2308 lines
86 KiB
HTML
2308 lines
86 KiB
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
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<html>
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<head>
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<title>The Answer Guy Issue 17</title>
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</head>
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<BODY BGCOLOR="EEE1CC" TEXT="#000000" LINK="#0000FF" VLINK="0020F0" ALINK=
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"FF0000">
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<!--endcut ========================================================= -->
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<H4>"Linux Gazette...<I>making Linux just a little more fun!</I>"
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</H4>
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<P> <hr> <P>
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<!-- =============================================================== -->
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<center>
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<H1><A NAME="answer">
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<img src="../gx/ans.gif" alt="" border=0 align=middle>
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The Answer Guy
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<img src="../gx/ans.gif" alt="" border=0 align=middle>
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</A></H1> <BR>
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<H4>By James T. Dennis
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<a href="mailto:jimd@starshine.org">jimd@starshine.org</a><BR>
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Starshine Technical Services, <A HREF="http://www.starshine.org/">
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http://www.starshine.org/</A> </H4>
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</center>
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<p><hr><p>
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<H3>Contents:</H3>
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<ul>
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<li><a HREF="./answer.html#fs">fs's</a>
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<li><a HREF="./answer.html#unix">Linux/Unix Emulator</a>
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<li><a HREF="./answer.html#vidX">Using X With 2 Monitors and 2 Video
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Cards</a>
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B
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<li><a HREF="./answer.html#host">Virtual Hosting</a>
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<li><a HREF="./answer.html#response">Response from Weitse Venema</a>
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<li><a HREF="./answer.html#file">Automatic File Transfer</a>
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<li><a HREF="./answer.html#ftpd">Installing wu-ftpd on a Linux Box</a>
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<li><a HREF="./answer.html#boot">Trying to Boot a Laptop</a>
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<li><a HREF="./answer.html#zmode">zmodem Reply</a>
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<li><a HREF="./answer.html#start">StartX</a>
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<li><a HREF="./answer.html#imap">IMAP and Linux</a>
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<li><a HREF="./answer.html#imap2">IMAP Again</a>
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<li><a HREF="./answer.html#uucp">UUCP Questions</a>
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<li><a HREF="./answer.html#flops">Using MS-DOS Floppies</a>
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<li><a HREF="./answer.html#inetd">inetd Questions</a>
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<li><a HREF="./answer.html#modem">Navas Modem FAQ</a>
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<li><a HREF="./answer.html#modem2">Setting Up a Modem</a>
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<li><a HREF="./answer.html#userid">User Identification</a>
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<li><a HREF="./answer.html#duplic">Duplicating a Linux Installed HD</a>
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</ul>
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<p><hr><p>
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<!--================================================================-->
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<a name="fs"></a>
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<h3><img align=bottom alt=" " src="../gx/ques.gif">
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fs's
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</h3>
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<P><B>
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From: Aaron M. Lee <a
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href="mailto:aaron@shifty.adosea.com">aaron@shifty.adosea.com</a><br>
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<p>Howdy Jim,
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My name's Aaron and I am sysadmin Cybercom Corp., an ISP in
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College Station, TX. We run nothing but Linux, and have been involved w/
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a lot of hacking and development on a number of projects. I have an
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unusual problem and have exhausted my resources for finding an answer- so
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i thought you might be able to help me out, if you've got the time.
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Anyway, here goes...
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<p>I've got a scsi disk I was running under Sparclinux that has 3
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partitions, 1 Sun wholedisk label, 2 ext2. That machine had a heart
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attack, and we don't have any spare Hypersparcs around- but I _really_
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need to be able to mount that drive to get some stuff off of it. I compiled
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in UFS fs support w/ Sun disklabel support into the kernel of an i386 Linux
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box, but the when I try to mount it, it complains that /dev/sd** isn't a
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valid block device, w/ either the '-t ufs' or '-t ext2' options. Also,
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fdisk thinks the fs is toast, and complains that the blocks don't end
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in physical boundaries (which is probably the case for an fdisk that
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doesn't know about Sun disklabels), and can't even tell that the
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partitions are ext2 (it thinks one of them is AIX!). Any ideas?
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</B><P>
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<img align=bottom alt=" " src="../gx/ans2.gif">
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Consider the nascent state of Sparc support for Linux
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I'm not terribly surprised that you're having problems.
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You seem to be asking:
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"How do I get Linux/Intel to see the fs on
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this disk?"
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<p> However I'm going to step back from the that question
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and ask the broader question:
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"How do you recover the (important) data off of
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that disk in a usable form?"
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<p> Then I'll step back even further and ask:
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"How important is that data? (what is its
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recovery worth to you)?"
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<p> ... and<br>
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"What were the disaster plans, and why
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are those plans inadequate for this
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situation?"
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<p> If you are like most ISP's out there -- you have not
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disaster or recovery plans, and little or no backup
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strategy. Your boss essentially asks you to running
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back and forth on the high wire at top speed -- without
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a net.
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<p> As a professional sysadmin you must resist the pressure
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to perform in this manner -- or at least you owe it to
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yourself to carefully spell out the risks.
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<p> In this case you had a piece of equipment that was
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unique the Sparc system -- so that any failure of
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any of its components would result in the lack of
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access to all data on that system.
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<p> Your question makes it clear that you didn't have
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sufficiently recent backups of the data on that
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system (otherwise the obvious solution would be
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to restore the data to some other system and
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reformat the drive in question).
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<p> My advice would be to rent (or even borrow) a
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SPARC system for a couple of days (a week is a
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common minimum rental period) -- and install
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the disk into that.
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<p> Before going to the expense of renting a system
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(or buying a used one) you might want to ensure
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that the drive is readable at the lowest physical
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level. Try the dd command on that device. Something
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like:
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<pre> dd if=/dev/sda | od | less
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</pre>
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<p> ... should let you know if the hardware is operational.
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If that doesn't work -- double and triple-check all of the
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cabling, SCSI ID settings, termination and other hardware
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compatibility issues. (You may be having some weird problem
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with a SCSI II differential drive connecting to an
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incompatible controller -- if this is an Adaptec 1542B
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-- be sure to break it in half before throwing it away
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to save someone else the temptation (the 1542C series is
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fine but the B series is *BAD*)).
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<p> Once you are reasonably confident that the hardware
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is talking to your system I'd suggest doing a direct,
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bitwise, dump of the disk to a tape drive. Just use a
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command like:
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<pre> dd if=/dev/sda of=/dev/st0
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</pre>
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<p> ... if you don't have a sufficiently large tape drive
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(or at least a sufficiently large spare hard disk) *and
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can't get one* than consider looking for a better
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employer.
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<p> Once you have a tape backup you can always get back
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to where you are now. This might not seem so great
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(since you're clearly not where you'd like to be) but
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it might be infinitely preferable to where you'll be
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if you have a catastrophic failure on mounting/fsck'ing
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that disk.
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<p> For the broader problem (the organizational ones rather
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Than the technical ones) -- you need to review
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the requirements and expectations of your employer --
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and match those against the resources that are being
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provided.
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<p> If they require/expect reliable access to their data --
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they must provide resources towards that end. The most
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often overlooked resource (in this case) is sysadmin
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time and training. You need the time to develop
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disaster/recovery plans -- and the resources to test
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them. (You'd be truly horrified at the number of sites
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that religiously "do backups" but have an entire staff that
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has never restored a single file from those).
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<p> Many organizations can't (or won't) afford a full spare
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system -- particularly of their expensive Sparc stations.
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They consider any system that's sitting on a shelf to be a
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"waste." -- This is a perfectly valid point of view.
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However -- if the production servers and systems are
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contributing anything to the companies bottom line --
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there should be a calculable cost for down time. If that's
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the case then there is a basis for comparison to the costs of
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rentals, and the costs of "spare" systems.
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<p> Organizations that have been informed of this risks and
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costs (by there IS staff) and continue to be unwilling or
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unable to provide the necessary resources will probably
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fail.
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<P><B><img align=bottom alt=" " src="../gx/ques.gif">
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Thanks in advance for any possible help,
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--Aaron
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</B><P>
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<img align=bottom alt=" " src="../gx/ans2.gif">
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It's often the case that I respond with things that
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I suspect my customer don't want to hear.
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The loss of this data (or the time lost to recovering
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it) is an opportunity to learn and plan -- you may
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prevent the loss of much more important information
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down the road if you now start planning for the
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inevitable hardware and system failures.
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<p><hr><p>
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<!--================================================================-->
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<a name="unix"></a>
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<h3><img align=bottom alt=" " src="../gx/ques.gif">
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Linux/Unix Emulator
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</h3>
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<P><B>
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From:Steven W., <a href="mailto:steven@gator.net">steven@gator.net</a><br>
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<p> Can you help me? Do you know of a Unix (preferably Linux) emulator
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that runs under Windows95?
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<p> -- Steven.
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</B><P>
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<img align=bottom alt=" " src="../gx/ans2.gif">
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Short Answer:
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I don't know of one.
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<p> Longer Answer:
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<p> This is a tough question because it really doesn't
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*mean* anything. An emulator is a piece of software
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that provide equivalent functionality to other software
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or hardware. Hopefully this software is indistinguishable
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from the "real" thing in all ways that count.
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<p> (Usually this isn't the case -- most VT100
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terminal emulation packages have bugs in them
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-- and that is one of the least complicated
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and most widespread cases of emulation in the
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world).
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<p> A Unix "emulator" that ran under Win '95 would probably not be
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of much use. However I have to ask what set of features
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you want emulated?
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<p> Do you want a Unix-like command shell (like
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Korn or Bash)? This would give you some of the
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"feel" of Unix.
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<p> Do you want a program that emulates one of the
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GUI's that's common on Unix? There are X Windows
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"display servers" (sort of like "emulators") that
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run under NT and '95. Quarterdeck's eXpertise
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would be the first I would try.
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<p> Do you want a program that allows you to run
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some Unix programs under Win '95? There are
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DOS, OS/2, and Windows (16 and 32 bit) ports of
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many popular Unix programs -- including most of
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the GNU utilities. Thus bash, perl, awk, sed,
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vi, emacs, tar, and hundreds of other utilities
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can be had -- most of them for free.
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<p> Do you want to run pre-compiled Unix binaries
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under Win '95? This would be a very odd request
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since there are dozens of implementations of
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Unix for the PC platform and hundreds for other
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architectures (ranging from Unicos on Cray super-
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computers to Minix and Coherent on XT's and 286's).
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Binary compatibility has playing only a tiny role
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in the overall Unix picture. I suspect that
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supporting iBCS (a standard for Unix binaries on
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intel processors -- PC's) under Win '95 would be a
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major technical challenge (and probably never
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provide truly satisfying results).
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<p> *note*: One of the papers presented at Usenix in
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Anaheim a couple of months ago discussed the
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feasibility of implementing an improved Unix
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subsystem under NT -- whose claim of POSIX support
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as proven to be almost completely useless in the
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real world. Please feel free to get a copy of
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the Usenix proceeding if you want the gory details
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on that. It might be construed as a "Unix emulation"
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for Windows NT -- and it might even be applicable to
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Win '95 -- with enough work.
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<p> If you're willing to run your Windows programs
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under Unix there's hope. WABI currently supports
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a variety of 16-bit Windows programs under Linux
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(and a different version support them under Solaris).
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Also work is continuing on the WINE project -- and
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some people have reported some success in running
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Windows 3.1 in "standard mode" under dosemu (the
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Linux PC BIOS emulator). The next version of WABI
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is expect to support (at least some) 32-bit Windows
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programs.
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<p> My suggestion -- if this is of any real importance to you --
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is that you either boot between Unix and DOS/Windows or that
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you configure a separate machine as a Unix host -- put it in
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a corner -- and using your Win '95 system as a terminal,
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telnet/k95 client and/or an X Windows "terminal" (display
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server).
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<p> By running any combination of these programs on your Windows
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box and connecting to your Linux/Unix system you won't have
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to settle for "emulation." You'll have the real thing --
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from both sides. In fact one Linux system can serve as the
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"Unix emulation adapter" for about as many DOS and Windows
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systems as you care to connect to it.
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<p> (I have one system at a client site that has about 32Mb
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of RAM and 3Gb -- it's shared by about 300 shell and
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POP mail users. Granted only about 20 or 30 of them are
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ever shelled at any given time but it's no where near it's
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capacity).
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<p> I hope this gives you some idea why your question is
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a little non-sensical. Operating systems can be viewed
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from three sides -- user interface (UI), applications
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programming interface (API), and supported hardware
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(architecture).
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<p> Emulating one OS under another might refer to emulating
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the UI, or the API or both. Usually emulation of the
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hardware support is not feasible (i.e. we can't run DOS
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device drivers to provide Linux hardware support).
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<p> If one implemented the full set of Unix system calls
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in a Win '95 program that provided a set of "drivers"
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to translate a set of Unix like hardware abstractions
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into calls to the Windows device drivers -- and one
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ported a reasonable selection of software to run under
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this "WinUnix kernel" -- one could call that "Unix emulation."
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<p> However it would be more accurate to say that you had
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implemented a new version of Unix on a virtual machine
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which you hosted under Windows.
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<p> Oddly enough this is quite similar to what the Lucent
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(Formerly Bell Labs?) Inferno package does. Inferno
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seems to have evolved out of the Plan 9 research project
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-- which apparently was Dennis Ritchie's pet project for
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a number of years. I really don't know enough about
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the background of this package -- but I have a CD
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(distributed to attendees of the aforementioned Usenix
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conference) which has demo copies of Inferno for several
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"virtual machine" platforms (including Windows and Linux).
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<p> Inferno is also available as a "native" OS for a couple
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of platforms (where it includes it's own device drivers
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and is compiled as direct machine code for a machine's
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platform).
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<p> One reason I mention Inferno is that I've heard that
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it offers features and semantics that are very similar
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to those that are common in Unix. I've heard it described
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as a logical outgrowth of Unix that eschews some of the
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accumulation of idiosyncrasies that has plagued Unix.
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<p> One of these days I'll have to learn more about that.
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<P><B>
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<img align=bottom alt=" " src="../gx/ques.gif">
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I have Windows95 and Linux on my system, on separate partitions, I
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can't afford special equipment for having them on separate machines.
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I really like Linux, and Xwindows, mostly because of their great
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security features. (I could let anybody use my computer without
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worrying about them getting into my personal files). Windows95's
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pseudo-multi-user system sucks really bad. So, mainly, this is why I
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like Linux. I also like the way it looks. Anyways, I would just run
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Linux but my problem is that Xwindows doesn't have advanced support
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for my video card, so the best I can get is 640x480x16colors and I
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just can't deal with that. Maybe I'm spoiled. The guy I wrote on
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the Xwin development team told me that they were working on better
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support for my card, though. (Aliance Pro-Motion). But, meanwhile,
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I can't deal with that LOW resolution. The big top-it-off problem is
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that I don't know of anyway to have Linux running _while_ Win95 is
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running, if there even is a way. If there was, it would be great,
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but as it is I have to constantly reboot and I don't' like it. So
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this is how I came to the point of asking for an emulator. Maybe
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that's not what I need after all. So what can I do? Or does the
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means for what I want not exist yet?
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<p>-- Steven.
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</B><P>
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<img align=bottom alt=" " src="../gx/ans2.gif">
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If you prefer the existing Linux/X applications and
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user interface -- and the crux of the problem is support
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for your video hardware -- focus on that. It's a simpler
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problem -- and probably offers a simpler solution.
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<p> There are basically three ways to deal with a lack of
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XFree86 support for your video card:
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<ul>
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<li> Help write an XFree86 driver
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(I'm not a coder either -- but I do occasionally
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beat the bushes and offer bribes to coder
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friends)
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<li> Look for Metro-X or other (probably commercial)
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support. (A copy of Metro-X comes with Red Hat
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4.1 for about $50 -- so this is not outrageously
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expensive).
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<li> Replace the video card. There are plenty of
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really good video cards that are supported by
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XFree86. Number 9, and Matrox have good track
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records. Some of the 2Mb PCI cards are only
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about $100 (US).
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</ul>
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<p> Be sure to contact the manufacturer to ask for a
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driver. Point out that they may be able to make
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small changes to an existing XFree86 driver. You
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can even offer to help them find a volunteer
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(where you post to the comp.os.linux.dev...sys.
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newsgroup and one or two of the developer's mailing
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lists -- and offer some support). Just offering to
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do some of the "legwork" maybe be a significant
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contribution.
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<p> This is an opportunity to be a "Linux-Activist."
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<p>--
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Jim
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<p><hr><p>
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<!--================================================================-->
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<a name="vidX"></a>
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<h3><img align=bottom alt=" " src="../gx/ques.gif">
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Using X with 2 Monitors and 2 Video Cards
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</h3>
|
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<P><B>
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From:Charles A. Barrasso<a
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href="mailto:charles@blitz.com">charles@blitz.com</a><br>
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I was wondering how I would go about using X with 2 monitors and 2
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video cards? I am currently using XFree86 window manager. I know you
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can do this with the MetroX window manager but that costs money :(.
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</B><P>
|
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<img align=bottom alt=" " src="../gx/ans2.gif">
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I'm sure I gave a lengthy answer to this fairly recently.
|
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Maybe it will appear in this month's issue (or maybe
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I answered it on a newsgroup somewhere).
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<p> In any event, the short answer is: You don't.
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<p> The PC architecture doesn't support using multiple
|
|
VGA/EGA cards concurrently. I don't think XFree86 can
|
|
work with CGA cards (and who'd want to!). You might
|
|
be able to get a Hercules compatible Monochrome Graphics
|
|
Adapter (MGA) to work concurrently with a VGA card (since
|
|
they don't use overlapping address spaces). I don't know
|
|
if this is the method that Metro-X supports.
|
|
|
|
<p> There are specialized video adapters (typically very expensive
|
|
-- formerly in the $3000+ range) that can co-exist with
|
|
VGA cards. Two sets of initials that I vaguely recall are
|
|
TIGA and DGIS. Considering that you seem unwilling to
|
|
pay $100 (tops) for a copy of Metro-X I think these --
|
|
even if you can still find any of them -- are way out of
|
|
your price league.
|
|
|
|
<p> Another, reasonable, alternative is to connect a whole
|
|
Xterminal or another whole system and run X on that. You
|
|
can then remotely display your windows on that about as
|
|
easily as you could set them to display on the local
|
|
server.
|
|
|
|
<p> (I know -- you might not get some cool window manager
|
|
to let you drag windows from one display server to another
|
|
-- a trick which I've seen done with Macs under MacOS and
|
|
with Suns and SGI's. But I've never set one of those up
|
|
anyway -- so I couldn't begin to help you there).
|
|
|
|
<p> You might double check with the Metro-X people to see
|
|
what specific hardware is required/supported by their
|
|
multiple display feature and then check with the XFree86.org
|
|
to see if anyone has any drivers for one of those supported
|
|
configurations.
|
|
|
|
<p> As a snide note I find your phrase "that costs money :("
|
|
to be mildly offensive. First the cost of an additional
|
|
monitor has got to be at least 3 times the price of
|
|
a copy of Metro-X. Second "free" software is not about
|
|
"not having to pay money."
|
|
|
|
<p> I'm not trying to sell you a copy of Metro-X here. I
|
|
don't use it -- and I specifically choose videos cards
|
|
that are supported by XFree86 when I buy my equipments.
|
|
|
|
<p> Likewise I don't recommend Linux to my customers because
|
|
it "doesn't cost them anything." In fact it does cost
|
|
them the time it takes me to install, configure and maintain
|
|
it -- which goes for about $95/hr currently. I recommend
|
|
Linux because it is a better tool for many jobs -- and because
|
|
the benefits of it's being "free" -- in the GNU sense of the
|
|
term -- are an assurance that no one can "have them over a
|
|
barrel" for upgrades or additional "licensing" fees. They are
|
|
always *free* to deploy Linux on as many systems as they want,
|
|
have as many users and/or processes as they want on any system,
|
|
make their own modifications to the vast majority of tools
|
|
on the system or hire any consultants they want to make the
|
|
customizations they need.
|
|
|
|
<p> I'm sorry to be so "political" here -- but complaining
|
|
that Metro-X "costs money" and asking me for a way to
|
|
get around that just cost me about $50 worth of my time.
|
|
Heck -- I'll go double or nothing -- send my your postal
|
|
address and I'll buy you a copy of RedHat 4.1. That comes
|
|
with a license for one installation of Metro-X and only
|
|
costs about $50. I'll even cover the shipping and handling.
|
|
|
|
<p> (Please call them first to make sure that it really does
|
|
support your intended hardware configuration).
|
|
|
|
<P><B><img align=bottom alt=" " src="../gx/ques.gif">
|
|
|
|
Thanks for the time,
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
|
|
No problem. (I did say "mildly" didn't I).
|
|
<p>
|
|
--
|
|
Jim
|
|
|
|
<p><hr><p>
|
|
<!--================================================================-->
|
|
|
|
<a name="host"></a>
|
|
<h3><img align=bottom alt=" " src="../gx/ques.gif">
|
|
Virtual Hosting
|
|
</h3>
|
|
<P><B>
|
|
From: Wietse Venema <a
|
|
href="mailto:wietse@wzv.win.tue.nl">wietse@szv.sin.tue.nl</a><br>
|
|
|
|
|
|
tcpd has supported virtual hosting for more than two years. Below
|
|
is a fragment from the hosts_access(5) manual page.
|
|
</B>
|
|
<p><B> Wietse
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
|
|
Thanks for the quick response. I'll have to play with
|
|
that. I suppose a custom "virtual finderd" would
|
|
be a good experiment.
|
|
|
|
<p> Do you know where there are any working examples of this
|
|
and the twist option posted to the 'net? I fight with
|
|
some of these and don't seem to get the right results.
|
|
|
|
<p> What I'd like is an example that drops someone into a
|
|
chroot'd jail as "nobody" or "guest" and running a
|
|
copy of lynx if they are from one address -- but
|
|
lets them log in a a normal user if they are from an
|
|
internal address. (We'll assume a good anti-spoofing
|
|
packet-filter on the router(s)).
|
|
|
|
<p> Did you ever add the chrootuid functionality to tcpd?
|
|
|
|
<p> How would you feel about an option to combine the
|
|
hosts.allow and hosts.deny into just tcpd.conf?
|
|
|
|
<p> (I know I can already put all the ALLOW and DENY
|
|
directives in a single file -- and I'm not much of a
|
|
programmer but even *I* could patch my own copy to
|
|
change the filename -- I'm just talking about the
|
|
general case).
|
|
|
|
|
|
|
|
<p> SERVER ENDPOINT PATTERNS<br>
|
|
In order to distinguish clients by the network address
|
|
that they connect to, use patterns of the form:
|
|
<pre>
|
|
process_name@host_pattern : client_list ...
|
|
</pre>
|
|
|
|
<p> (which is what he said one to me when I suggested merging
|
|
his chrootuid code with tcpd).
|
|
|
|
<p> I've blind copied Wietse on this (Hi!). I doubt he has
|
|
time to read the Linux Gazette.
|
|
|
|
|
|
--
|
|
Jim
|
|
|
|
<p><hr><p>
|
|
<!--================================================================-->
|
|
|
|
<a name="response"</a>
|
|
<h3><img align=bottom alt=" " src="../gx/ques.gif">
|
|
Response from Weitse Venema
|
|
</h3>
|
|
<P><B>
|
|
From:Wietse Venema, <a href="mailto:wietse@wzv.win.tue.nl">wietse@wzv.win.tue.nl</a><br>
|
|
|
|
Do you know where there are any working examples of this
|
|
and the twist option posted to the 'net? I fight with
|
|
some of these and don't seem to get the right results.
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
|
|
Use "twist" to run a service that depends on destination address:
|
|
|
|
fingerd@host1: ALL: twist /some/where/fingerd-for-host1
|
|
<P><B>
|
|
<img align=bottom alt=" " src="../gx/ques.gif">
|
|
What I'd like is an example that drops someone into a
|
|
chroot'd jail as "nobody" or "guest" and running a
|
|
copy of lynx if they are from one address -- but
|
|
lets them log in a a normal user if they are from an
|
|
internal address. (We'll assume a good anti-spoofing
|
|
packet-filter on the router(s)).
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
|
|
I have a little program called chrootuid that you could use.
|
|
<P><B>
|
|
<img align=bottom alt=" " src="../gx/ques.gif">
|
|
Did you ever add the chrootuid functionality to tcpd?
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
|
|
I would do that if there was a performance problem. Two small
|
|
programs really is more secure than a bigger one.
|
|
<P><B>
|
|
|
|
<img align=bottom alt=" " src="../gx/ques.gif">
|
|
How would you feel about an option to combine the
|
|
hosts.allow and hosts.deny into just tcpd.conf?
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
|
|
What about compatibility with 1 million installations world-wide?
|
|
<P><B>
|
|
<img align=bottom alt=" " src="../gx/ques.gif">
|
|
(I know I can already put all the ALLOW and DENY
|
|
directives in a single file -- and I'm not much of a
|
|
programmer but even *I* could patch my own copy to
|
|
change the filename -- I'm just talking about the
|
|
general case).
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
This is because the language evolved over time. Compatibility can
|
|
become a pain in the rear.
|
|
|
|
<p>--
|
|
Weitse
|
|
|
|
<p><hr><p>
|
|
<!--================================================================-->
|
|
|
|
<a name="file"></a>
|
|
<h3><img align=bottom alt=" " src="../gx/ques.gif">
|
|
Automatic File Transfer
|
|
</h3>
|
|
<P><B>
|
|
From:Kenneth Ng, <a href="mailto:kenng@kpmg.com">kenng@kpmg.com</a><br>
|
|
|
|
In Linux Gazette, there is a mention of how to transfer files
|
|
automatically using ftp.
|
|
|
|
Here is how:
|
|
<pre>
|
|
#!/bin/csh
|
|
ftp -n remote.site << !
|
|
user joe blow
|
|
binary
|
|
put newfile
|
|
quit
|
|
!
|
|
</pre>
|
|
</B>
|
|
<p><B>And that's it. Granted ssh is better. But sometimes you have to go
|
|
somewhere that
|
|
only supports ftp.
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
That's one of several ways. Another is to use ncftp
|
|
-- which supports things like a "redial" option to keep
|
|
trying a busy server until it gets through. ncftp also has
|
|
a more advanced macro facility than the standard .netrc (FTP).
|
|
|
|
<p> You can also use various Perl and Python libraries (or classes)
|
|
to open ftp sessions and control them. You could use 'expect'
|
|
to spawn and control the ftp program.
|
|
|
|
<p> All of these methods are more flexible and much more robust
|
|
than using the standard ftp client with redirection ("here"
|
|
document or otherwise).
|
|
<p>
|
|
--
|
|
Jim
|
|
|
|
<p><hr><p>
|
|
<!--================================================================-->
|
|
|
|
<a name="ftpd"></a>
|
|
<h3><img align=bottom alt=" " src="../gx/ques.gif">
|
|
Installing wu-ftpd on a Linux Box
|
|
</h3>
|
|
<P><B>
|
|
From: Stephen P. Smith, <a href="mailto:ischis@evergreen.com">ischis@evergreen.com</a><br>
|
|
|
|
I just installed wu-ftpd on my linux box. I have version 2.4.
|
|
I can login under one of my accounts on the system and everything
|
|
works just fine.
|
|
</B>
|
|
<p><B>If I try an anonymous ftp session, the email password is rejected.
|
|
|
|
what are the possible sources of failure?
|
|
where should i be going for more help? :-)
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
|
|
Do you have a user named 'ftp' in the /etc/passwd file?
|
|
<P><B><img align=bottom alt=" " src="../gx/ques.gif">
|
|
done.
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
|
|
wu-ftpd takes that as a hint to allow *anonymous* FTP.
|
|
If you do have one -- or need to create one -- be sure that
|
|
the password for it is "starred out." wu-ftpd will not
|
|
authenticate against the system password that's defined for a
|
|
a user named "ftp."
|
|
<P><B><img align=bottom alt=" " src="../gx/ques.gif">
|
|
done.
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
|
|
You should also set the shell to something like /bin/false or
|
|
/bin/sync (make sure that /bin/false is really a binary and
|
|
*not* a shell script -- there are security problems -- involve
|
|
IFS (inter-field separators) if you use a shell script in the
|
|
/etc/passwd shell field).
|
|
<P><B><img align=bottom alt=" " src="../gx/ques.gif">
|
|
done.
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
|
|
There is an FAQ for anonymous FTP (that's not Linux specific).
|
|
There is also a How-To for FTP -- that is more Linux oriented.
|
|
If you search Yahoo! on "wu-ftp" you'll find the web pages
|
|
at Washington University (where it was created) and at
|
|
academ.com -- a consulting service that's taken over development
|
|
of the current beta's.
|
|
<P>
|
|
<img align=bottom alt=" " src="../gx/ques.gif">
|
|
<B>Guess I will just have to do it the hard
|
|
way. Will tell you what I find (just in
|
|
case you want to know.
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
|
|
What does your /etc/ftpaccess file look like?
|
|
|
|
<p> Did you compile a different path for the ftpaccess file
|
|
(like /usr/local/etc/)?
|
|
|
|
<p> What authentication libraries are you using (old
|
|
fashioned DES hashes in the /etc/passwd, shadow,
|
|
shadow with MD5 hashes -- like FreeBSD's default,
|
|
or the new PAM stuff)?
|
|
|
|
<p> Is this invoked through inetd.conf with tcpd
|
|
(the TCP Wrappers)? If so, what does your /var/log/messages
|
|
say after a login failure? (Hint: use the command:
|
|
'tail -f /var/log/messages > /dev/tty7 &' to leave a continuously
|
|
updated copy of the messages file sitting on one of your
|
|
-- normally unused -- virtual consoles).
|
|
<p>
|
|
One trick I've used to debug inetd launched programs (like
|
|
ftpd and telnetd) is to wedge a copy of strace into the
|
|
loop. Change the reference to wu.ftpd to trace.ftpd --
|
|
create a shell or perl script named trace.ftpd that consists
|
|
of something like:
|
|
<pre>
|
|
#! /bin/sh
|
|
exec strace -o /tmp/ftpd.strace /usr/sbin/wu.ftpd
|
|
</pre>
|
|
<p> ... and then inspect the strace file for clues about
|
|
what failed. (This is handy for finding out that the
|
|
program couldn't find a particular library or configuration
|
|
file -- or some weird permissions problems, etc).
|
|
|
|
<p>
|
|
--
|
|
Jim
|
|
|
|
|
|
<p><hr><p>
|
|
<!--================================================================-->
|
|
|
|
<a name="boot"></a>
|
|
<h3><img align=bottom alt=" " src="../gx/ques.gif">
|
|
Trying to Boot a Laptop
|
|
</h3>
|
|
<P><B>
|
|
From: Yash Khemani, <a href="mailto:khemani@plexstar.com">khemani@plexstar.com</a><br>
|
|
|
|
I've got a Toshiba satellite pro 415cs notebook computer on which I've
|
|
installed RedHat 4.1. RedHat 4.1 was installed on a jaz disk connected
|
|
via an Adaptec slimscsi pcmcia adapter. the installation went
|
|
successfully, i believe, up until the lilo boot disk creation. i
|
|
specified that i wanted lilo on a floppy - so that nothing would be
|
|
written to the internal ide drive and also so that i could take the
|
|
installation and run it at another such laptop. after rebooting, i
|
|
tried booting from the lilo floppy that was created, but i get nothing
|
|
but continuous streams of 0 1 0 1 0 1...
|
|
</B>
|
|
<p><B>i am guessing that the lilo floppy does not have on it the pcmcia
|
|
drivers. what is the solution at this point to run RedHat on this
|
|
machine?
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
|
|
You've got the right idea.
|
|
The 1010101010101... from LILO is a dead giveaway that
|
|
your kernel is located on some device that cannot be
|
|
accessed via the BIOS.
|
|
|
|
<p> There are a couple of ways to solve the problem.
|
|
I'd suggest LOADLIN.EXE.
|
|
|
|
<p> LOADLIN.EXE is a DOS program (which you might have
|
|
guessed by the name) -- which can load a Linux kernel
|
|
(stored as a DOS file) and pass it parameters (like
|
|
LILO does). Basically LOADLIN loads a kernel (Linux or
|
|
FreeBSD -- possibly others) which then "kicks" DOS
|
|
"out from under it." In other words -- it's a one-way
|
|
trip. The only way back to DOS is to reboot (or
|
|
run dosemu ;-) .
|
|
|
|
<p> LOADLIN is VCPI compatible -- meaning that it can run
|
|
from a DOS command prompt even when you have a memory
|
|
manager (like QEMM) loaded. You can also set LOADLIN
|
|
as your "shell" in the CONFIG.SYS. That's particularly
|
|
handy if you're using any of the later versions of DOS
|
|
that support a multi-boot CONFIG.SYS (or you're using the
|
|
MBOOT.SYS driver that provided multi-boot features in
|
|
older versions of DOS).
|
|
|
|
<p> To use LOADLIN you may have to create a REALBIOS.INT
|
|
file (a map of the interrupt vectors that are set by
|
|
your hardware -- before any drivers are loaded).
|
|
To do this you use a program (REALBIOS.EXE) to create
|
|
a special boot floppy, then you boot off that floppy
|
|
(which records the interrupt vector table in a file)
|
|
-- reboot back off your DOS system and run the second
|
|
stage of the REALBIOS.EXE.
|
|
|
|
<p> This little song and dance may be necessary for each
|
|
hardware configuration. (However you can save and
|
|
copy each of the REALBIOS.INT files if you have a
|
|
couple of configurations that you switch between --
|
|
say, with a docking station and without).
|
|
|
|
<p> With LOADLIN you could create a DOS bootable floppy,
|
|
with a copy of LOADLIN.EXE and a kernel (and the
|
|
REALBIOS.INT -- if it exists). All of that will
|
|
just barely fit on a 1.44M floppy.
|
|
|
|
<p> Another way to do this would be to create a
|
|
normal DOS directory on your laptop's IDE drive --
|
|
let's call it C:\LINUX (just to be creative).
|
|
|
|
<p> Then you'd put your LOADLIN.EXE and as many different
|
|
kernels as you liked in that directory -- and maybe
|
|
a batch file (maybe it could be called LINUX.BAT) to
|
|
call LOADLIN with your preferred parameters. Here's a
|
|
typical LINUX.BAT:
|
|
<pre>
|
|
@ECHO OFF
|
|
ECHO "About to load Linux -- this is a one-way trip!"
|
|
PAUSE
|
|
LOADLIN lnx2029.krn root=/dev/sda1 ro
|
|
</pre>
|
|
<p> (where LNX2029.KRN might be a copy of the Linux-2.0.29
|
|
kernel -- with a suitable DOS name).
|
|
|
|
<p> I'd also recommend another batch file (SINGLE.BAT) that
|
|
loads Linux in single-user mode (for fixing things when
|
|
they are broken). That would replace the LOADLIN line
|
|
in the LINUX.BAT with a line like:
|
|
|
|
<pre> LOADLIN lnx2029.krn single root=/dev/sda ro
|
|
</pre>
|
|
<p> Another way to do all of this is to simply dd a
|
|
properly configured kernel to a floppy. You use the
|
|
rdev command to patch the root device flags in the
|
|
kernel and dump it to a floppy. This works because
|
|
a Linux kernel is designed to work as a boot image.
|
|
The only problem with this approach is that it doesn't
|
|
allow you to pass any parameters to your kernel (to
|
|
force single user mode, to select an alternate root
|
|
device/filesystem, or whatever).
|
|
|
|
<p> For other people who have a DOS system and want to
|
|
try Linux -- but don't want to "commit" to it with
|
|
a "whole" hard drive -- I recommend DOSLINUX.
|
|
|
|
<p> A while back there was a small distribution called
|
|
MiniLinux (and another called XDenu) which could
|
|
install entirely within a normal DOS partition --
|
|
using the UMSDOS filesystem. Unfortunately MiniLinux
|
|
has not been maintained -- so it's stuck with a 1.2
|
|
kernel and libraries.
|
|
|
|
<p> There were several iterations of a distribution called
|
|
DILINUX (DI= "Drop In") -- which appears to have eventually
|
|
evolved into DOSLINUX. The most recent DOSLINUX seems was
|
|
uploaded to the Incoming at Sunsite within the last two
|
|
weeks -- it includes a 2.0.29 kernel.
|
|
|
|
<p> The point MiniLinux and DOSLINUX is to allow one to install
|
|
a copy of Linux on a DOS system as though it were a DOS
|
|
program. DOSLINUX comes as about 10Mb of compressed
|
|
files -- and installs in about 20-30Mb of DOS file space.
|
|
It includes Lynx, Minicom, and a suite of other utilities
|
|
and applications.
|
|
|
|
<p> All in all this is a quick and painless way to try Linux.
|
|
So, if you have a DOS using friend who's sitting on the fence,
|
|
give them a copy of DOSLINUX and show them how easy it is.
|
|
|
|
<p><img align=bottom alt=" " src="../gx/ques.gif">
|
|
<P><B>
|
|
thanks!<br>
|
|
yash
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
|
|
You're welcome.
|
|
|
|
(Oh -- you might want to get those shift keys fixed --
|
|
e.e. cummings might sue for "look and feel")
|
|
|
|
<p>
|
|
--
|
|
Jim
|
|
|
|
<p><hr><p>
|
|
<!--================================================================-->
|
|
|
|
<a name="zmode"></a>
|
|
<h3><img align=bottom alt=" " src="../gx/ques.gif">
|
|
zmodem Reply
|
|
</h3>
|
|
|
|
From: Donald Harter Jr., <a href="mailto:harter@mufn.org">harter@mufn.org</a><br>
|
|
|
|
I saw your post about zmodem in the Linux Gazette. I can't answer the
|
|
readers question, but maybe this will help. My access to the internet is a
|
|
dial in account(no slip, no ppp). I access the freenets. I can't use
|
|
zmodem to transfer files from the internet and freeenets to my pc. I can
|
|
use kermit though. It seems that there are some control characters involved
|
|
in zmodem that prevent it from being used with my type of connection. I saw
|
|
a some information about this on one of the freenets. They suggested using
|
|
telix and another related protocol. I tried that, but it didn't work
|
|
either. Kermit is set up to run slow. You can get kermit to go faster in
|
|
certain circumstances by executing its "FAST" macro. I can download data at
|
|
about 700cps with the "FAST" macro of kermit. Unfortunately kermit hangs up
|
|
the line for me so I have to "kill -9 kermitpid" to exit it. That problem
|
|
can probably be eliminated with the right compile options. In certain cases
|
|
I can't use the "FAST" macro when uploading.
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
|
|
I'm familiar with C-Kermit. In fact I may have an
|
|
article in the June issue of SysAdmin magazine on that very
|
|
topic.
|
|
|
|
<p> The main points of my article are that C-Kermit is a
|
|
telnet and rlogin client as well as a serial communications
|
|
program -- and that it is a scripting language that's
|
|
available on just about every platform around.
|
|
|
|
<p> I know about Telix' support for the kermit transfer protocol.
|
|
It sucks. On my main system I get about 1900 cps for
|
|
ZMODEM transfers -- about 2200 for kermit FAST (between
|
|
a copy of C-Kermit 5A(188) and 6.0.192 and about 70 cps
|
|
(yes -- seventy!) between a copy of C-Kermit and Telix'
|
|
internal kermit.
|
|
|
|
<p> Other than that I've always liked Telix. Minicom has
|
|
nice ncurses and color -- but is not nearly as featureful
|
|
or stable as either Telix for DOS or any version of C-Kermit.
|
|
|
|
<p> Your line hangups probably have to do with your settings for
|
|
carrier-watch. Try SET CARRIER-WATCH OFF or ON and see if
|
|
it still "hangs" your line. I suspect that its actually just
|
|
doing read() or write() calls in "blocking" mode. You might
|
|
have to SET FLOW-CONTROL NONE, too. There are lots of
|
|
C-Kermit settings. If you continue to have trouble -- post
|
|
a message to the comp.protocols.kermit.misc newsgroup
|
|
(preferred) or send a message to kermit-support@columbia.edu.
|
|
|
|
<p> When I first started using C-Kermit (all of about two months
|
|
ago) my initial questions where answered by Frank da Cruz
|
|
himself (he's the creator of the Kermit protocol and the
|
|
technical lead of the Kermit project at Columbia University).
|
|
(That was before he knew that I'm a "journalist" -- O.K.
|
|
quit laughing!). Frank is also quite active in the newsgroup.
|
|
I think he provides about 70 or 80 per cent of the technical
|
|
support for the project.
|
|
|
|
<p> Oh yeah! If you're using C-Kermit you should get the
|
|
_Using_C-Kermit_ book. It was written by Frank da Cruz and
|
|
Christine Gianone -- and is the principal source of funding
|
|
for the Kermit project. From what I gather a copy of the
|
|
book is your license to use the software.
|
|
<p>
|
|
--
|
|
Jim
|
|
|
|
|
|
<p><hr><p>
|
|
<!--================================================================-->
|
|
|
|
<a name="start"></a>
|
|
<h3><img align=bottom alt=" " src="../gx/ques.gif">
|
|
StartX
|
|
</h3>
|
|
<P> <B>
|
|
From: Robert Rambo, <a href="mailto:robert.rambo@yale.edu">robert.rambo@yale.edu</a><br>
|
|
|
|
Hi, I was wondering if you can help me out. When I use the command
|
|
'startx -- -bpp16' to change the color depth, the windows in X are much
|
|
bigger than the monitor display. So, nothing fits properly and
|
|
everything has become larger. But the color depth has changed
|
|
correctly. I use FVWM as my display manager. Is there some way to fix
|
|
this problem?
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
If using the 16 bit plan (16bpp) mode to increase
|
|
your color depth -- that suggests that selecting this
|
|
mode is causing the server to use a lower resolution.
|
|
|
|
<p> That is completely reasonable. If you have a 2Mb video
|
|
card and you run it in 1024x768x256 or 1024x768x16 --
|
|
then you try to run it with twice as many colors --
|
|
the video RAM has to come from somewhere. So it
|
|
bumps you down to 800x600 or 640x480. These are just
|
|
examples. I don't deal with graphics much so I'd have
|
|
to play with a calculator to figure the actual maximum
|
|
modes that various amounts of video RAM could support.
|
|
|
|
<p> There are alot of settings in the XConfig file. You
|
|
may be able to tweak them to do much more with your
|
|
existing video card. As I've said before -- XConfig
|
|
files are still magic to me. They shifted from blackest
|
|
night to a sort of charcoal gray -- but I can't do them
|
|
justice in a little article hear. Pretty much I'd have
|
|
to lay hands on it -- and mess with it for a couple of
|
|
hours (and I'm definitely not the best one for that job).
|
|
|
|
<p> If you haven't upgraded to a newer XFree86 (3.2?) then
|
|
this would be a good time to try that. The newer one
|
|
is much easier to configure and supports a better selection
|
|
of hardware -- to a better degree than the older versions.
|
|
I haven't heard of any serious bugs or problems with
|
|
the upgrades.
|
|
|
|
<p> You may also want to consider one of the commercial servers.
|
|
Definitely check with them in advance to be absolutely certain
|
|
that your hardware is supported before you buy. Ask around in
|
|
the newsgroups for opinions about your combination of hardware.
|
|
It may be that the XFree86 supports you particular card better
|
|
than Metro-X or whatever.
|
|
|
|
<p> You may also want to look at beefing up your video hardware.
|
|
As I've said -- I don't know the exact figures -- but I'd
|
|
say that you probably need a 4Mb card for anything like
|
|
16bpp at 1024x768. You should be able to look up the
|
|
supported modes in your card's documentation or on the
|
|
manufacturer's web site or BBS.
|
|
|
|
|
|
<B><P><img align=bottom alt=" " src="../gx/ques.gif">
|
|
Also, is there some way to change the color depth
|
|
setting to start X with a depth of 16 every time. I do not use the XDM
|
|
manager to initiate an X session.
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
|
|
Yes -- it's somewhere in that XConfig file. I don't
|
|
remember the exact line. I really wish a bona fide GUI
|
|
X wiz would sign up for some of this "Answer Guy" service.
|
|
|
|
<p> It doesn't matter whether you use xdm or not. If you
|
|
put the desired mode in the XConfig file. However --
|
|
since you don't you could just write your own wrapper
|
|
script, alias or shell function to call 'startx' with
|
|
the -- -bpp16 options. You could even re-write 'startx'
|
|
(it is just a shell script). That may seem like cheating --
|
|
but it may be easier than fighting your way through the
|
|
XConfig file (do you get the impression that I just don't
|
|
like that thing -- it is better than a WIN.INI or a
|
|
SYSTEM.INI -- but not be much).
|
|
|
|
|
|
<p>
|
|
--
|
|
Jim Dennis,
|
|
|
|
<p><hr><p>
|
|
<!--================================================================-->
|
|
|
|
<a name="imap"></a>
|
|
<h3><img align=bottom alt=" " src="../gx/ques.gif">
|
|
IMAP and Linux
|
|
</h3>
|
|
<P> <B>
|
|
From: Brian Moore, <a
|
|
href="mailto:bem@thorin.cmc.net">bem@thorin.cmc.net</a><br>
|
|
|
|
Being a big IMAP fan (and glad to see it finally getting recognition:
|
|
Netscrape 4 and IE4 will both support it), your answer left a lot out.
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
|
|
Will these support the real features (storing and
|
|
organizing folders on the server side)?
|
|
|
|
<p> I heard that NS "Communicator" (the next release
|
|
Netscape's Navigator series is apparently going to
|
|
come with a name change) supports IMAP -- but it's
|
|
possible to implement this support as just a variant
|
|
of POP -- get all the message and immediately
|
|
expunge all of them from the server.
|
|
|
|
<p> It seems that this is how Eric S. Raymond's 'fetchmail'
|
|
treating IMAP mail boxes -- as of about 2.5 (it seems
|
|
that he's up to 3.x now)
|
|
|
|
<P><img align=bottom alt=" " src="../gx/ques.gif">
|
|
<B>The easiest IMAP server to install is certainly the University of
|
|
Washington server. It works, handles nearly every mailbox format around
|
|
and is very stable. It's also written by the guy in charge of the IMAP
|
|
spec itself, Mark Crispin.
|
|
|
|
As for clients, there is always Pine, which knows how to do IMAP quite
|
|
well. This is part of most Linux distributions as well.
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
|
|
I did mention pine. However it's not my personal favorite.
|
|
|
|
Do you know of a way to integrate IMAP with emacs mh-e/Gnus
|
|
(or any mh compatible folder management system)?
|
|
|
|
<P>
|
|
<img align=bottom alt=" " src="../gx/ques.gif">
|
|
<B>For GUI clients there is ML, which is a nice client, but requires Motif
|
|
and can be slow as sin over a modem when you have a large mailbox.
|
|
That's available in source at
|
|
http://www-CAMIS.Stanford.EDU/projects/imap/ml
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
|
|
I thought I mentioned that one as well -- but it's
|
|
a blur to me.
|
|
|
|
<p> I personally avoid GUI's like the plague. I'm
|
|
typing this from my laptop, through a null modem link
|
|
to my machine in the other room.
|
|
|
|
<p> I run emacs under screen -- so I can use mh-e for most
|
|
mail, Gnus for netnews and for some of my mailing lists
|
|
(it can show news folders as though they were threaded
|
|
news groups). screen allows me to detach my session from
|
|
my terminal so I can log out, take off with the laptop,
|
|
and re-attach to the same session later (via modem or when
|
|
I get back home).
|
|
|
|
<P>
|
|
<img align=bottom alt=" " src="../gx/ques.gif">
|
|
<B>Asking on the mailing list about static linked linux versions will get
|
|
you one (and enough nagging may get them to actually put one of the
|
|
current version up).
|
|
|
|
ML is really the nicest mail client I have ever used.
|
|
|
|
As for pop daemons with UIDL support, go for qpopper from qualcomm.
|
|
ftp.qualcomm.com somewhere. Has UIDL and works fine.
|
|
</B><P>
|
|
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
|
|
O.K. I'll at that to my list.
|
|
|
|
<p> Does that one also support APOP's authentication
|
|
mechanism (which I gather prevents disclosing your
|
|
password over an untrusted network by using something
|
|
like an MD5 hash of your password concatenated with
|
|
a date and time string -- or something like that)?
|
|
|
|
<p> Does qpopper allow you to maintain a POP user account
|
|
file that's separate from your /etc/passwd file?
|
|
|
|
<p> Do you know of an IMAP server that supports these
|
|
sorts of features (secure authentication and separate
|
|
user base)?
|
|
|
|
<p> (I know this probably seems like a switch -- the
|
|
so called "Answer Guy" asking all the questions --
|
|
but hey -- I've got to get my answers from *somewhere*)
|
|
|
|
<p>
|
|
--
|
|
Jim
|
|
|
|
<p><hr><p>
|
|
<!--================================================================-->
|
|
<a name="imap2"></a>
|
|
<h3><img align=bottom alt=" " src="../gx/ques.gif">
|
|
More IMAP
|
|
</H3><P> <B>
|
|
From: Graham Todd, <a href="mailto:gtodd@yorku.ca">gtodd@yorku.ca</a>
|
|
<br>
|
|
|
|
PINE - one of the easiest to use mail clients around - does IMAP just
|
|
fine. You can read mail from multiple servers and mailboxes and save
|
|
it locally or in remote folders on the servers - which is what IMAP is
|
|
all about: Internet Message Access Protocol = flexible and
|
|
configurable *access* to mail servers without having to pop and fetch
|
|
messages all over the place (but still having the ability save locally
|
|
if you want).
|
|
</B>
|
|
<p><B>The Netscape's Communicator 4.0b2 thing does too but there are so many
|
|
other ugly bits that I'm not gonna bite.
|
|
</B>
|
|
<p><B>Jeez pretty soon with this fancy new IMAP stuff you'll be able to do
|
|
almost as much as you can right now with emacs and ange-ftp (which I
|
|
use regularly to access remote mail folders and boxes with out having
|
|
to login - it's all set up in .netrc).
|
|
|
|
Of course the answer is almost always "emacs" .... BTW Linux
|
|
makes a GREAT program loader for emacs ;-)
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
|
|
Seems kind of kludgey. Besides -- does that
|
|
give you the main feature that's driving the creation
|
|
of the IMAP/ACAP standards? Does it let you
|
|
store your mail on a server and replicate that to
|
|
a couple of different machines (say your desktop and
|
|
your laptop) so you can read and respond to mail "offline"
|
|
and from *either* system?
|
|
|
|
<P><B><img align=bottom alt=" " src="../gx/ques.gif">
|
|
|
|
Yeah, more or less. If you save the mail on your server to local
|
|
folders or make a local folder be /me@other.mail.host:/usr/spool/me.
|
|
Using ange-ftp to me seem exactly like IMAP in Pine or Netscape
|
|
communicator 4.0b2. Though apparently IMAP will update folders across
|
|
hosts so that only that mail deleted locally (while offline) will get
|
|
deleted on the remote host on the next login etc. etc. I don't know
|
|
much about IMAP's technical standard either but find I get equal mail
|
|
management capability from ange-ftp/VM. (equal to Pine and
|
|
Communicator so far).
|
|
</B>
|
|
<p><B>WARNING: In a week or so when I get time I'm gonna ask you a tricky
|
|
question about emacs and xemacs.
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
|
|
Feel free. Of course I do know a bit more about emacs
|
|
than I do about X -- so you may not like my answer much.
|
|
|
|
<P><B><img align=bottom alt=" " src="../gx/ques.gif">
|
|
|
|
Heh heh OK...
|
|
|
|
|
|
(comp.emacs.xemacs is silent on this). Emacs running as emacs -nw in
|
|
a tty (i.e console or an xterm) runs fine and lets me use all the job
|
|
control commands (suspend/fg etc) but with Xemacs job control won't
|
|
work unless I'm running as root. That is if I'm running "xemacs" or
|
|
"xemacs -nw" in an xterm or at the console and do C-z and then once
|
|
I'm done in the shell I do "fg", xemacs comes back but the keyboard
|
|
seems to be bound to the tty/console settings (Ctrl-z Ctrl-s Ctrl-q
|
|
etc all respond as if I were in a dumb terminal). The only recourse
|
|
is to Ctrl-z back out and kill xemacs. This does not happen if I run
|
|
xemacs setuid root (impractical/scary) or as root (scary). Something
|
|
somewhere that requires root permission or suid to reset the tty
|
|
characteristics doesn't have it in xemacs - but does in emacs...
|
|
|
|
My only response so far has been that "you'll have to
|
|
rebuild/recompile your xemacs" - but surely this wrong. Does anything
|
|
more obvious occur to you? I feel it must be something simple in my
|
|
set up (RH Linux 2.0.29). Of course if I could get this fixed I'd
|
|
start feeling more comfortable not having GNU-Emacs on my machine ;-)
|
|
which may not be an outcome you would favour.
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
|
|
I once had a problem similar to this one -- suspending
|
|
minicom would suspend the task and lock me out of it.
|
|
|
|
It seemed that the ownership of the tty was being
|
|
changed.
|
|
|
|
<p> So -- the question comes up -- what permissions are set on
|
|
your /dev/tty* nodes. It seems that most Linux distributions
|
|
are set up to have the login process chown the these to to the
|
|
current user (and something seems to restore them during or after
|
|
logout).
|
|
|
|
<p> I don't know enough about the internals of this process.
|
|
I did do a couple of experiments with the 'script' command
|
|
and 'strace' using commands like:
|
|
|
|
<pre> strace -o /tmp/strace.script /usr/bin/script</pre>
|
|
|
|
<p> ... and eyeballing the trace file. This shows how the
|
|
script command (which uses a psuedo tty -- or pty) searches
|
|
for an available device.
|
|
|
|
<p> I then did a simple 'chown 600 /dev/ttyp*' as root
|
|
(this leaves a bunch of /dev/ttyq* and /dev/ttyr nodes
|
|
available). The 'script' command then reports that
|
|
the system is "out of pty's."
|
|
|
|
<p> Obviously the script command on my system don't
|
|
do a very thorough search for pty's. It effectively
|
|
only looks at the first page of them.
|
|
|
|
<p> The next test I ran was to add a new line to my
|
|
/etc/services file (which I called stracetel) -- and
|
|
a new line to me /etc/inetd.conf that referred to it.
|
|
|
|
<p> This line looks like this:
|
|
<pre>
|
|
stracetel stream tcp nowait root /usr/sbin/tcpd \
|
|
/usr/bin/strace -o /root/tmp/t.strace /usr/sbin/in.telnetd
|
|
</pre>
|
|
<p> ... all on one line, of course.
|
|
|
|
<p> Then I connected to that with the command:
|
|
|
|
<pre> telnet localhost stracetel</pre>
|
|
|
|
<p> This gives me an strace of how telnetd handles the
|
|
allocation and preparation of a pty. Here, as I suspected,
|
|
I saw chown() and chmod() calls after telnetd did it's
|
|
search through to list of pty's to find the first one.
|
|
|
|
<p> Basically both programs (and probably most other
|
|
pty clients) attempt to open each pty until one returns
|
|
a valid file descriptor or handle. (It might be nice
|
|
if there was a system call or a daemon that would allow
|
|
programs to just say "give me a pty" -- rather than forcing
|
|
a flurry of failed open attempts -- but that's probably too
|
|
much to ask for.
|
|
|
|
<p> There result of these experiments suggests that there
|
|
are many ways of handling pty's -- and some of them may
|
|
have to be set as compile time options for your system.
|
|
|
|
<p> It may be that you just need to make all the pty's
|
|
mode 666 (which they are on my system) or you might
|
|
chgrp them to a group like tty or pty, make them mode
|
|
660 and make all the pty using programs on your system
|
|
SGID.
|
|
|
|
<p> I've noticed that all of my pty's are 666 root.root
|
|
(my tty's root.tty and ttyS*'s are root.uucp all are
|
|
mode 660 and all programs that need to open them are
|
|
either root run (getty) or SGID as appropriate).
|
|
|
|
<p> Some of the policies for ownership and permissions are
|
|
set my your distribution. Red Hat 2.x is *old* and
|
|
some of these policies may have changed in the 3.03 and
|
|
4.1 releases. Mine is a 3.03 with *lots* of patches,
|
|
updated RPM's and manually installed tarballs.
|
|
|
|
<p> Frankly I don't know *all* of the security implications
|
|
of having your /dev/tty* set to mode 666. Obviously
|
|
normal attempt to open any of these while they're in
|
|
use return errors (due to the kernel locking mechanisms).
|
|
Other attempts to access them (through shell redirection,
|
|
for example) seem to block on I/O. I suspect that a
|
|
program that improperly opened it's tty (failed to
|
|
set the "exclusive" flag on the open call) would be
|
|
vulnerable.
|
|
|
|
|
|
<p> Since you're an emacs fan -- maybe you can tell me --
|
|
is there an mh-e/Gnus IMAP client?
|
|
|
|
<P><B><img align=bottom alt=" " src="../gx/ques.gif">
|
|
|
|
|
|
No Kyle Jones (VM maintainer/author) has said maybe IMAP4 for VM
|
|
version 7. I think his idea is to make VM do it what it does well and
|
|
rely on outside packages to get the mail to it ...
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
|
|
Also -- isn't there a new release of ange-ftp --
|
|
I forget the name -- but I'm sure it changed named too.
|
|
<img align=bottom alt=" " src="../gx/ques.gif">
|
|
<P><B>
|
|
Yes it's called EFS - it preserves all the functionality but is more
|
|
tightly meshed with dired - supposedly it will be easier to use EFS in
|
|
other elisp packages (I don't know why or how this would be so).
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
|
|
I'll have to play with those a bit.
|
|
Can VM handle mh style folders?
|
|
<p>
|
|
--
|
|
Jim
|
|
|
|
<p><hr><p>
|
|
<!--================================================================-->
|
|
|
|
<a name="uucp"></a>
|
|
<h3><img align=bottom alt=" " src="../gx/ques.gif">
|
|
UUCP Questions
|
|
</h3>
|
|
<P> <B>
|
|
From: David J. Weis, <a
|
|
href="mailto:weisd3458@uni.edu">weisd3458@uni.edu</a><br>
|
|
|
|
|
|
I had a couple minor questions on UUCP. If you have a few minutes, I'd
|
|
appreciate the help immensely. I'll tell you a little bit about what we're
|
|
doing.
|
|
</B><P>
|
|
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
|
|
Glancing ahead -- I'd guess that this would take quite a bit
|
|
more than a few minutes.
|
|
<P>
|
|
<img align=bottom alt=" " src="../gx/ques.gif">
|
|
<B>My company has a domain name registered (plconline.com) and two offices.
|
|
One is the branch office which is located in the city with the ISP. The
|
|
head office is kind of in the sticks in western Iowa. I've been
|
|
commissioned to find out how difficult it would be to set up the uucp so
|
|
the machine in Des Moines (the big city ;-) would grab all the domain mail
|
|
and then possibly make a subdomain like logan.plconline.com for all the
|
|
people in the main office to use email.
|
|
</B>
|
|
<p><B>This would all be running on RedHat 4 over dialup uucp. The system in Des
|
|
Moines uses uucp over tcp because it has to share the line with
|
|
masquerading, etc.
|
|
</B>
|
|
<p><B>Thanks for any advice or pointers you have.
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif"><br>
|
|
|
|
Unfortunately I this question is too broad to answer
|
|
via e-mail. O'Reilly has a whole book on uucp and
|
|
there are several HOW-TO's for Taylor UUCP and
|
|
sendmail under Linux.
|
|
|
|
<p> My uucp mostly works but I haven't configured it to
|
|
run over TCP yet. I also haven't configured my
|
|
system to route to any uucp hosts within my domain.
|
|
|
|
<p> You can address mail to a uucp host through a
|
|
DNS by using the '%' operator. For example I can
|
|
get my main mail system (antares.starshine.org) to
|
|
forward mail to my laptop using an address like:
|
|
|
|
<pre> jim%mercury@starshine.org</pre>
|
|
|
|
<p> ... the DNS MX record for starshine.org routes
|
|
mail to my ISP. My ISP then spools it up in UUCP
|
|
until my machine (antares) picks it up. The
|
|
name antares is basically transparent to most of
|
|
this process.
|
|
|
|
<p> When antares gets the mail it converts the
|
|
percent sign into a "bang" (!) and spools it
|
|
for mercury (which happens to be my laptop).
|
|
|
|
<p> Obviously requiring all of your customers and
|
|
correspondents to use percent signs in their addressing
|
|
to your users is not going to work very well. It will
|
|
probably result in alot of lost mail, alot of complaints
|
|
and a constant barrage of support calls.
|
|
|
|
<p> There are two ways to make your internal mail routing
|
|
transparent to the rest of world. You can create a
|
|
master aliases list on your mail hub (the easy way) or
|
|
you can create DNS and MX entries for each of the hosts.
|
|
|
|
<p> If you'd like more help we could arrange to talk on
|
|
the phone. UUCP is difficult to set up for the first
|
|
time (nearly vertical initial learning curve). Once it's
|
|
set up it seems to be pretty low maintenance. However
|
|
my meta-carpus can't handle explaining the whole process
|
|
via e-mail (and I don't understand enough of it well to
|
|
be brief).
|
|
|
|
<p>
|
|
--
|
|
Jim
|
|
|
|
|
|
<p><hr><p>
|
|
<!--================================================================-->
|
|
|
|
<a name="flops"></a>
|
|
<h3><img align=bottom alt=" " src="../gx/ques.gif">
|
|
Using MS-DOS Floppies
|
|
</h3>
|
|
<P> <B>
|
|
From: Barry, <a
|
|
href="mailto:remenyi@hotmail.com">remenyi@hotmailcom</a><br>
|
|
|
|
Hi, I have a problem that I can't find the solution to:
|
|
</B>
|
|
<p><B>I run Redhat 4.1 with mtools already installed, with it, I can copy a
|
|
file to or from a dos disk in A: with mcopy etc..
|
|
But if I change the disk & do mdir, it tells gives me the listing of
|
|
what was in the last disk. The only solution is to wait hours for the
|
|
cache to expire before I can look at another disk.
|
|
</B>
|
|
<p><B>The problem occurs no matter how I access the floppy, I also tried using
|
|
dosemu, and mount, but I have the same problem. I can read and write
|
|
from the first disk that I put in with no problems, but if I change the
|
|
disk, the computer acts as if the first disk is still in the drive. It
|
|
also doesn't matter who I am loged in as eg. root has the same problem.
|
|
I also upgraded mtools to 3.3 but no change.
|
|
</B>
|
|
<p><B>Is there some way to disable the disk cache (I assume thats the problem)
|
|
for the floppy drive?
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
|
|
You probably have a problem with the "change disk" detection
|
|
circuitry on your floppy.
|
|
|
|
<p> There's a pretty good chance that you'd see the same thing
|
|
under DOS too.
|
|
|
|
<p> Unfortunately I don't know of an easy way to solve this
|
|
problem. You could try replacing the floppy ($30 or so)
|
|
the controller ($20 -- to ???) and/or the cable.
|
|
|
|
<p> If that's not feasible in your case you could try something
|
|
like a mount/sync/umount (on a temporary mount point).
|
|
This might force the system to detect the new floppy. It's
|
|
very important not to try to write anything to a floppy when the
|
|
system is confused about which floppy is in there.
|
|
|
|
<p> DOS systems that I have used -- while they were afflicted
|
|
with this problem -- sometimes severely trash the directories
|
|
on a diskette in that situation.
|
|
|
|
<p> It probably doesn't even matter if the mount, sync, umount
|
|
that I describe fails -- just so the system is forced to
|
|
"rethink" what's there. I'd consider writing a short script
|
|
to do this -- put a temporary mount point that's "user" accessible
|
|
to avoid having to be root to do this (and especially to avoid
|
|
having to create any SUID root perl scripts or write a C wrapper
|
|
or any of that jazz).
|
|
|
|
<p> Here's a sample line for your /etc/fstab:
|
|
|
|
<pre># /etc/fstab
|
|
/dev/fd0 /mnt/tmp umsdos noauto,rw,user 0 0</pre>
|
|
|
|
<p> (according to my man pages the "user" options should
|
|
imply the nosuid, nodev etc. options -- which prevent
|
|
certain other security problems).
|
|
|
|
<p> So your chdisk script might look something like:
|
|
|
|
<pre> #! /bin/sh
|
|
/bin/mount /mnt/tmp
|
|
/bin/sync
|
|
/bin/umount /mnt/tmp</pre>
|
|
|
|
<p> ... you could also just do a 'mount /mnt/tmp' or a
|
|
'mount /mnt/a' or whatever you like for your system --
|
|
and just use normal Linux commands to work with those
|
|
files. The mtools are handy sometimes -- but far from
|
|
indispensable on a Linux system with a good fstab
|
|
file.
|
|
|
|
<p> As a security note: mount must be SUID in order to
|
|
allow non-root users to mount filesystems. Since
|
|
there have been security exploits posted on mount
|
|
specifically and various other SUID files chronically,
|
|
I suggest configuring mount and umount such that they
|
|
can only be executed by members of a specific group
|
|
(like a group called "disk" or "floppy"). Then you
|
|
can add yourself and any other users who have a valid
|
|
reason to work at your console to that group. Finally
|
|
change the permissions on mount and umount to something
|
|
like:
|
|
|
|
<pre> -r-sr-x--- 1 root disk .... /bin/mount</pre>
|
|
|
|
<p> .... i.e. don't allow "other" to execute it.
|
|
|
|
<p> This also applies to all your SVGALib programs (which
|
|
should not be executed except from the console) and
|
|
as many of your other SUID programs as you can.
|
|
|
|
<p> (... it would be nice to do that to sendmail -- and
|
|
I've heard it's possible. However it's a bit trickier
|
|
than I've had time to mess with on this system).
|
|
|
|
<p> As PAM (pluggable authentication module) technology
|
|
matures you'll be able to configure your system to
|
|
dynamically assign group membership's based on
|
|
time of day and source of login (value of `tty`).
|
|
|
|
<p> This will be nice -- but it doesn't appear to be
|
|
quit ready yet.
|
|
|
|
<p>
|
|
--
|
|
Jim
|
|
<P><B>
|
|
<img align=bottom alt=" " src="../gx/ques.gif">
|
|
|
|
I just wanted to write to thank you for you response to my mail.
|
|
I did as you suggested and the problem is solved!
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
|
|
Actually, you were also right about the problem occurring in DOS as
|
|
I used to have a lot of floppies go bad before I went all the way
|
|
to linux, but I didn't make the connection.
|
|
<P><B>
|
|
<img align=bottom alt=" " src="../gx/ques.gif">
|
|
Anyway, thanks again, you've made my day!
|
|
</B>
|
|
<p><B>Barry
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
You're welcome. I'm glad it wasn't something complicated.
|
|
BTW: which suggestion worked for you? Replacing one or
|
|
another componenent? Or did you just use the "mount, sync,
|
|
umount" trick?
|
|
|
|
<p> Under DOS I used to use Ctrl-C, from the COMMAND.COM A:
|
|
prompt to force disk change detection. You can use that
|
|
if you still boot this machine under DOS for some work.
|
|
<p>
|
|
--
|
|
Jim
|
|
|
|
<p><hr><p>
|
|
<!--================================================================-->
|
|
|
|
<a name="inetd"></a>
|
|
<h3><img align=bottom alt=" " src="../gx/ques.gif">
|
|
inetd Questions
|
|
</h3>
|
|
<P> <B>
|
|
From: Benjamin Peikes, <a href="mailto:benp@npsa.com">benp@npsa.com</a><br>
|
|
|
|
Answer guy,<br>
|
|
|
|
I have two questions for you.
|
|
</B>
|
|
<p><B> 1) I'm using one machine with IPAliasing and was wondering if
|
|
there is a version of inetd built so that you can have different
|
|
servers spawned depending on the ip number connected to.
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
|
|
That's an excellent question.
|
|
|
|
There is apparently no such feature or enhanced version of
|
|
inetd or xinetd.
|
|
|
|
<p> It also doesn't appear to be possibly to use TCP Wrapper
|
|
rules (tcpd, and the /etc/hosts.allow and /etc/hosts.deny)
|
|
to implement this sort of virtual hosting.
|
|
|
|
<p> So far it appears that all of the support for virtual hosting
|
|
is being done by specific applications. Apache and some other
|
|
web servers have support for it. The wu-ftpd's most recent
|
|
versions support it.
|
|
|
|
<p> I suspect that you could create a special version of
|
|
inetd.conf to open sockets on specific local IP addresses
|
|
and listen on those. I would implement that as a command
|
|
line option -- passing it a regex and/or list of ip addresses
|
|
to listen on after the existing command line option to
|
|
specify which configuration file to use. Then you'd load
|
|
different copies of this indetd with commands like:
|
|
|
|
<pre> /usr/sbin/inetd /etc/inetd.fred 192.168.14.0 17.18.0.0
|
|
/usr/sbin/inetd /etc/inetd.barney barneyweb
|
|
/usr/sbin/inetd /etc/inetd.wilma 192.168.2.3
|
|
</pre>
|
|
<p> (This would be something like -- all of the 192.168.14.*
|
|
address and all of the 17.18.*.* addresses are handled by
|
|
the first inetd -- all of the access to a host named
|
|
barneyweb (presumably looked up through the /etc/hosts file)
|
|
would be handled by the next inetd. and all of the accesses
|
|
to the ipalias 192.168.2.3 would be handled by the last one)
|
|
|
|
<p> This would allow one to retain the exact format of the
|
|
existing inetd files.
|
|
|
|
<p> However I don't know enough about sockets programming to
|
|
know how much code this would entail. The output of
|
|
'netstat -a' on my machine here shows the system listening
|
|
on *:smtp and *:telnet (among others). I suspect that those
|
|
stars would show up different if I had a socket open to
|
|
a specific service on a specific service.
|
|
|
|
<p> This scheme might use up to many file descriptors. Another
|
|
approach would be to have a modified tcpd. This would have
|
|
to have some option where by the destination *as well as*
|
|
the source was matched in the /etc/tcpd.conf file(s).
|
|
|
|
<p> (Personally I think that tcpd should be compiled
|
|
with a change -- so that the single tcpd.conf
|
|
file is used in preference to the /etc/hosts.allow
|
|
and /etc/hosts.deny files. Current versions do
|
|
support the single conf file -- but the naming is
|
|
still screwy).
|
|
|
|
<p> I'm not sure quite how Wietse would respond to this --
|
|
possibly by repeating the question:
|
|
|
|
<p> "If you want me to add that -- what should I
|
|
take OUT?"
|
|
|
|
<p> (which is what he said one to me when I suggested merging
|
|
his chrootuid code with tcpd).
|
|
|
|
<p> I've blind copied Wietse on this (Hi!). I doubt he has
|
|
time to read the Linux Gazette.
|
|
<P>
|
|
<img align=bottom alt=" " src="../gx/ques.gif">
|
|
<B>2) A related problem: I have one machine running as a mail server
|
|
for several domains where the users are using pop to get their
|
|
mail. The problem is that the From: line always has the name
|
|
of the server on it. Is there a way to use IPaliasing to fix
|
|
this? Or do I have to muck around with the sendmail.conf file?
|
|
</B><P>
|
|
|
|
<p> This is becoming a common question.
|
|
|
|
<p> Here's a couple of pointers to web sites and FAQ or HOWTO
|
|
documents that deal specifically with "Virtual Mail Hosting"
|
|
<ul>
|
|
<li><a href="http://www.sinbad.wantabe.com/virtualmail">How to Set up Sendmail for Virtual Domains</a>
|
|
<li><a href="http://www.qmail.org">qmail: A Replacement for Sendmail</a>
|
|
</ul>
|
|
<p> (look for references to "virtualdomains")
|
|
|
|
<p> ... and here's one guide to Virtual Web Hosting:
|
|
<ul>
|
|
<li><a href="http://inorganic5.fdt.net/ldp/HOWTO/mini/Virtual-Web">
|
|
Virtual Web Mini-HOWTO</a>
|
|
</ul>
|
|
<P>
|
|
<img align=bottom alt=" " src="../gx/ques.gif">
|
|
<B>I guess the best way to do this would be to change inetd to figure
|
|
out on which interface the connection has been made on and then
|
|
pick the correct inetd.conf to reference, like
|
|
<pre>
|
|
inetd.conf.207.122.3.8
|
|
inetd.conf.207.122.3.90</pre>
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
I would recommend that as a default behavior.
|
|
I suggested adding additional parameters to the
|
|
command line specifically because it could be done
|
|
without breaking any backward compatibility. The
|
|
default would be to simply work as it does now.
|
|
|
|
<p> I still suspect that this has some scalability problems
|
|
-- it might not be able to handle several hundred or several
|
|
thousand aliased addresses.
|
|
|
|
<p> I might still be useful to implement it as a variation of --
|
|
or enhancement to -- tcpd (TCP_Wrappers).
|
|
<P>
|
|
<img align=bottom alt=" " src="../gx/ques.gif">
|
|
<B>I think that inetd reads in the configuration file when it
|
|
starts because it needs a SIGHUP to force it to reread the conf
|
|
file. All you would have to do is make it reference the right table.
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
|
|
This is also documented in the inetd man page.
|
|
<P>
|
|
<img align=bottom alt=" " src="../gx/ques.gif">
|
|
<B>Do you know where I could find the code? I would be interested
|
|
in looking at it?
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
|
|
The source code from inetd should be in the bundle
|
|
of sources that comes with the "NetKit"
|
|
|
|
<p> Look to:
|
|
|
|
<p><a href="ftp://ftp.inka.de/pub/comp/Linux/networking/NetTools/">ftp:..ftp.inka.de/pub/comp/Linux/networking/NetTools/</a>
|
|
|
|
<p> and mirrored at:
|
|
|
|
<p><a href="ftp://ftp.uk.linux.org/pub/linux/Networking/PROGRAMS/NetTools/>ftp://ftp.uk.linux.org/pub/linux/Networking/PROGRAMS/NetToos/</a>
|
|
|
|
<p> More information about Linux network code can be
|
|
found at:
|
|
|
|
<p><a href="ftp://sunsite.unc.edu/pub/Linux/system/network/NET-3-HOWTO">ftp://sunsite.unc.edu/pub/Linux/system/network/NET-3-HOWTO/</a>
|
|
|
|
<p> ... this includes the history of it's development and the
|
|
names of people who were active in it at various stages.
|
|
|
|
<p> If you're going to try to hack this together -- I'd suggest
|
|
a friendly posting to the comp.linux.development.system
|
|
newsgroup -- and possibly some e-mail to a couple of
|
|
carefully chosen people in the NET-3-HOWTO.
|
|
<p>
|
|
--
|
|
Jim
|
|
|
|
<p><hr><p>
|
|
<!--================================================================-->
|
|
|
|
<a name="modem"></a>
|
|
<h3><img align=bottom alt=" " src="../gx/ques.gif">
|
|
Navas Modem FAQ
|
|
</h3>
|
|
<P> <B>
|
|
From: John Doe
|
|
<br>
|
|
The next time you answer a modem question, you'd do well
|
|
to recommend reading of the very good Navas Modem FAQ at
|
|
<a href="http://www.aimnet.com/~jnavas/modem/faq.html">http://www.aimnet.com/~jnavas/modem/faq.html/</a>
|
|
</B><P><img align=bottom alt=" " src="../gx/ans2.gif">
|
|
|
|
Well, here's someone who wants to make a anonymous
|
|
tip to "The Answer Guy."
|
|
|
|
|
|
<p>At "John Doe's" request I looked over this site. It
|
|
does have extensive information about modems -- including
|
|
lots of press releases about which companies are acquiring
|
|
each other (3Com over US Robotics, Quarterdeck gets DataStorm).
|
|
|
|
<p>However there didn't appear to be any references to Linux,
|
|
Unix or FreeBSD.
|
|
|
|
<p>So -- if one needs information about modems in general this
|
|
looks like an excellent site to visit. However it the question
|
|
pertains specifically to using your modem with Linux -- I'd
|
|
suggest:
|
|
|
|
<a href="http://sunsite.unc.edu/LDP/HOWTO/Serial-HOWTO.html">http://sunsite.unc.edu/LDP/HOWTO/Serial-HOWTO.html</a>
|
|
|
|
<p>
|
|
--
|
|
Jim
|
|
|
|
<p><hr><p>
|
|
<!--================================================================-->
|
|
|
|
<a name="modem2"></a>
|
|
<h3><img align=bottom alt=" " src="../gx/ques.gif">
|
|
Setting Up a Modem
|
|
</h3>
|
|
<P> <B>
|
|
From: Yang, <a href="mailto:lftian@ms.fudan.edu.cn">lftian@ms.fudan..edu.cn</a>
|
|
</br>
|
|
I have an AT 3300 card( from Aztech) which integrates the function of
|
|
sound card and 28.8K modem. It seems that it need a special driver for its
|
|
modem function to be work. In MSDOS, there is a aztpnp.exe for that
|
|
purpose. Do you know is there any way I can get the card work (at least its
|
|
modem function) in Linux?
|
|
</B><p>
|
|
<B>Tianming Yang
|
|
</B><P><img align=bottom alt=" " src="../gx/ans2.gif">
|
|
|
|
I'm not familiar with that device. The
|
|
name of the driver suggests that this is a
|
|
Plug 'n Play (pnp) device (sometimes we use the
|
|
phrase "plug and *pray*" -- as it can be a toss
|
|
of the dice to see if they'll work as intended.
|
|
|
|
<p> My guess would be that this is a PCMCIA card
|
|
for a laptop system (which I personally pronounce
|
|
"piecemeal").
|
|
|
|
<p> Did you look in the "Hardware HOWTO" (start at
|
|
www.ssc.com, online mirror of FAQ's and HOWTO's)?
|
|
|
|
<p> Did you go to Yahoo! and do a keyword search on
|
|
the string:
|
|
|
|
<pre> linux +aztech</pre>
|
|
|
|
<p> ... (the plus sign is important there)?
|
|
|
|
<p> Since all of the real details about the configuration
|
|
of the card are determined by the manufacturer
|
|
(Aztech in this case) I would start by contacting
|
|
them.
|
|
|
|
<p> If they've never heard of Linux -- or express no
|
|
interest in supporting it -- please consider letting
|
|
them know that Linux support affects your purchasing
|
|
decisions. Also let them know that getting support
|
|
for Linux is likely to cost them very little.
|
|
|
|
|
|
<p> How to get a Linux driver for your hardware:
|
|
|
|
<p> If you are a hardware company that would like
|
|
to provide support for Linux and FreeBSD and other
|
|
operating systems -- but you don't have the
|
|
development budget -- just ask.
|
|
|
|
<p> That's right. Go to the comp.os.linux.development.system
|
|
newsgroups and explain that you'd like to provide
|
|
full documentation and a couple of units of your hardware
|
|
to a team of Linux programmers in exchange for a freely
|
|
distributable driver. Be sure to make the sources for
|
|
one of your other drivers (preferably any UNIX, DOS, or
|
|
OS/2 driver) available to them.
|
|
|
|
<p> If you don't like that approach, consider publishing the
|
|
sources to your existing drivers. If you are really in
|
|
the hardware business than the benefits of diverse OS
|
|
support should far outweigh any marginal "edge" you might
|
|
get from not letting anyone see "how you do it."
|
|
|
|
<p> (Just a suggestion for all those hardware vendors out there).
|
|
<p>
|
|
--
|
|
Jim
|
|
|
|
<p><hr><p>
|
|
<!--================================================================-->
|
|
|
|
<a name="userid"></a>
|
|
<h3><img align=bottom alt=" " src="../gx/ques.gif">
|
|
User Identification
|
|
</h3><P> <B>
|
|
From: Dani Fricker, <a
|
|
href="mailto:101550.3160@CompuServe.COM">101550.3160@CompuServe.COM</a>
|
|
<br>
|
|
i need your help. for some reasons i have to identify a user on my
|
|
webserver by his/her ip-address. fact is that users logon comes from
|
|
different physical machines. that means that i have to assign something
|
|
like a virtual ip-address to a users log name. something like a reversal
|
|
masquerading.
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
The IP Address of any connecting client is provided
|
|
to any CGI scripts you run, and is stored in the
|
|
server's access log (or a reverse DNS lookup of it
|
|
is stored therein -- depending on your httpd and
|
|
configuration).
|
|
|
|
<p> * Note: I suggest disabling reverse DNS
|
|
lookup on webserver wherever possible.
|
|
it generates alot of unnecessary traffic
|
|
and you can isolate, sort, and look up the
|
|
IP addresses in batches when you want to
|
|
generate statistics involving domain names.
|
|
|
|
<p> (I also tend to think that most of the
|
|
reports done on web traffic logs have about
|
|
as much rigor and resemblance to statistical
|
|
analysis as reading chicken entrails).
|
|
<P>
|
|
<img align=bottom alt=" " src="../gx/ques.gif">
|
|
<B>my ip-gateway connects my inner lan over two token ring network cards
|
|
(sorry, not my idea!) with the internet (lan <-> tr0 <-> tr1 <->
|
|
internet). the masquerading forward roule of ipfwadm gives me the
|
|
possibility to indicate a source and a destination address.
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
|
|
Oh. So all of the clients that you're interested in
|
|
are on a private LAN and going through a masquerading/NAT
|
|
server (network address translation).
|
|
|
|
<p> I would try using ident for starters. Run identd on your
|
|
Masquerade Host and make calls to the ident service from
|
|
your CGI scripts. I don't think it will work -- but it
|
|
should be worth a little info.
|
|
|
|
<p> From there you might be able to configure all the clients
|
|
on the inner LAN to use an *applications* level proxy
|
|
(squid -- formerly cached, CERN httpd, or the apache cache/
|
|
proxy server). Masquerading can be thought of as a
|
|
"network layer proxying services" while SOCKS, and similar
|
|
services -- which work with the co-operation of the client
|
|
software -- are applications layer proxies.
|
|
|
|
<p> I don't know if the private net IP address or other info
|
|
will propagate through any of these HTTP proxies.
|
|
|
|
<p> If this is *really* important to you, you could consider
|
|
writing your own "NAT Ident" service and client. I don't
|
|
know how difficult that would be -- but it seems like the
|
|
code for the identd (and the RFC 931? spec) might give you
|
|
a starting point for defining a protocol (you might want
|
|
to secure that service under TCP_Wrappers). You might want
|
|
to consider making this a TCP "Multiplexed" service --
|
|
look for info on tcpmux for details about that.
|
|
|
|
<p> The gist of tcpmux is that it allows your custom client
|
|
to talk to a daemon on TCP port 1 of the server host and
|
|
ask for a service by name (rather than relying on
|
|
"Well-Known Port Addresses"). So, if you're going to create
|
|
a new service -- it makes sense to put it under tcpmux
|
|
so you don't pick your own port number for it -- and then
|
|
have the IANA assign that port to something else that you
|
|
might want later.
|
|
<P><img align=bottom alt=" " src="../gx/ques.gif">
|
|
<B>do you see a possibility for an 'address assignment' between the two
|
|
interfaces? if you do please let me know.
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
I don't know of any existing way to determine the IP
|
|
address of a client on the other side of any NAT/masquerading
|
|
host -- I'm not even sure if there's any existing way to do it
|
|
for a client behind a SOCKS or TIS FWTK or other applications
|
|
level proxy.
|
|
|
|
<p> I'll be honest. With most "Answer Guy" questions I
|
|
do some Yahoo!, Alta-vista and SavvySearch queries -- and
|
|
ask around a bit (unless I already know the answer pretty
|
|
well -- which doesn't happen all that often these days).
|
|
I skipped that this time -- since I'm pretty sure that
|
|
there's nothing out there that does this.
|
|
|
|
<p> I welcome any corrections on this point. I'll be happy
|
|
to forward any refutations and corrections to Dani.
|
|
|
|
<p> All of this begs the greater question:
|
|
|
|
<p> What are you really trying to do?
|
|
|
|
<p> If you are trying to provide some form of transparent
|
|
access control to your webserver (so local users can
|
|
see special stuff without using a "name and password")
|
|
-- there are better ways available.
|
|
|
|
<p> Netscape and Internet Explorer both support a form
|
|
of client-certificate SSL -- which is supported at
|
|
the server side by the Stronghold (commercial Apache)
|
|
server.
|
|
|
|
<p> As an alternative -- I'd look at the possibility of
|
|
finding or writing a Kerberos "auth" module for
|
|
Apache (and deploying Kerberos to the clients).
|
|
This might be more involved than you're management
|
|
is willing to go for -- but writing new variations of
|
|
the indentd service might also fall into that category.
|
|
|
|
<p> IP addresses are a notoriously bad form of access
|
|
control. If you have a properly configured set of
|
|
anti-spoofing rules in the packet filters on your
|
|
router -- and you can show that no other routes exist
|
|
into your LAN -- then you can base access controls to
|
|
services (TCP/Wrappers) to about the granularity of
|
|
"from here" and "not from here." Attempting to read
|
|
more into them than that is foolhardy.
|
|
|
|
<p> Ethernet and Token Ring MAC (media access control) addresses
|
|
(sometimes erroneously called "BIA's" -- burned in addresses)
|
|
are just about as bad (most cards these days have options to
|
|
over-ride the BIA with another MAC -- usually a feature of
|
|
operating the card in "promiscuous" mode).
|
|
|
|
<p> Yet another approach to the problem might be to simply
|
|
put a web server on the internal LAN (no routing through
|
|
the NAT/masquerading host) -- and use something like
|
|
rdist to replication/mirror the content between the
|
|
appropriate document trees on the internal and exterior
|
|
web servers.
|
|
|
|
<p> Basically we'd need to know much more about your
|
|
requirements in order to give relevant recommendations.
|
|
|
|
|
|
<p>
|
|
--
|
|
Jim
|
|
|
|
<p><hr><p>
|
|
<!--================================================================-->
|
|
|
|
<a name="duplic"></a>
|
|
<h3><img align=bottom alt=" " src="../gx/ques.gif">
|
|
Duplicating a Linux Installed HD
|
|
</h3><P> <B>
|
|
From: Mohammad A. Rezaei, <a href="mailto:rezaei@tristan.TN.CORNELL.EDU">rezaei@tristan.TN.CORNELL.EDU</a><br>
|
|
|
|
I just read your response to duplicating a hard drive using dd.
|
|
I think using dd limits the uses of this technique too much.
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
|
|
I absolutely agree. I wonder where I suggested 'dd'
|
|
without expressing my misgivings.
|
|
|
|
<p> Please consider quoting little portions of my posting
|
|
when making references to them -- I write alot and
|
|
can't remember past postings without some context.
|
|
<P>
|
|
<img align=bottom alt=" " src="../gx/ques.gif">
|
|
<B>I have more than once installed/transfered entire hard drives using
|
|
tar. simply put both drives in the same machine, mount the new drive
|
|
in /mnt and do something like
|
|
<pre>
|
|
tar -c -X /tmp/excludes -f / | (cd /mnt; tar xvf -)
|
|
The file....
|
|
|
|
/tmp/excludes should contain:
|
|
|
|
/mnt
|
|
/proc
|
|
and any other non-local, mounted drives, such as nfs mount points.
|
|
</pre>
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
|
|
There are better ways to do this.
|
|
|
|
One way is to use a command like:
|
|
<pre>
|
|
find ... -xdev -type f | tar cTf - - | \
|
|
(cd ... && tar xpf - )
|
|
|
|
Another is to use:
|
|
|
|
find ... | cpio pvum /new/directory
|
|
|
|
... which I only learned after years of using
|
|
the tar | (cd ... && tar) construct.
|
|
</pre>
|
|
|
|
<p> In both of these cases you can use find parameters
|
|
to include just the files that you want. (Note:
|
|
with tar you *must* prevent find from printing any
|
|
directory names by using the -type f (or more
|
|
precisely a \! -type d clause) -- since tar will
|
|
default to tar'ing any directories named in a
|
|
recursive fashion).
|
|
|
|
<p> The -T (capital "tee") option to GNU tar means to
|
|
"Take" a list of files as an "include" list. It
|
|
is the complement to the -X option that you list.
|
|
|
|
<p> You can also pipe the output of your find through
|
|
grep -v (or egrep -v) to filter out a list of
|
|
files that you want to exclude.
|
|
<P><B><img align=bottom alt=" " src="../gx/ques.gif">
|
|
|
|
finally, one has to install the drive onto the new machine,
|
|
boot from floppy and run lilo.
|
|
|
|
The disks don't have to be identical. the only disadvantage is having
|
|
to run lilo, but that's takes just a few minutes.
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
|
|
The only message I can remember posting about 'dd'
|
|
had an extensive discussion of using tar and cpio for
|
|
copying trees.
|
|
|
|
Am I forgetting one -- or did you only get part of
|
|
my message?
|
|
|
|
<P><B><img align=bottom alt=" " src="../gx/ques.gif">
|
|
|
|
Hope this helps.
|
|
</B><P>
|
|
<img align=bottom alt=" " src="../gx/ans2.gif">
|
|
|
|
Hopefully it will help some readers. The issues of
|
|
copying file trees and doing differential and
|
|
incremental backups is one that is not well covered in
|
|
current books on system administration.
|
|
|
|
<p> When I do a full backup I like to verify that it
|
|
was successful by extracting a table of contents or
|
|
file listing from the backup media. I then keep a
|
|
compressed copy of this. Here I use tar:
|
|
<pre>
|
|
tar tf /dev/st0 | gzip > /root/tapes.contents/.....
|
|
</pre>
|
|
<p> .... where the contents list is named something like:
|
|
<pre>
|
|
antares-X.19970408
|
|
</pre>
|
|
<p> .... which is a hostname, a volume (tape) number and a
|
|
date in YYYYMMDD format (for proper collation -- sorting).
|
|
|
|
<p> To do a differential I use something like:
|
|
|
|
<pre> find / -newer /root/tape.contents/.... \
|
|
| egrep -v "^(/tmp|/proc|/var/spool/news)" \
|
|
| tar czTf - /mnt/mo/diff.`date +%Y%m%d`.tar
|
|
</pre>
|
|
<p> ... (actually it's more complicated than that since
|
|
I build the list and compute the size -- and do some
|
|
stuff to make sure that the right volume is on the
|
|
Magneto Optical drive -- and mail nastygrams to myself
|
|
if the differential won't fit on that volume -- if the
|
|
volume is the most recent one (I don't overwrite the
|
|
most recent -- I rotate through about three generations)
|
|
-- etc).
|
|
|
|
<p> However this is the core of a differential backup.
|
|
If you wanted an incremental -- you'd supply a different
|
|
file to the -newer switch on your find command.
|
|
|
|
<p> The difference between differential and incremental is
|
|
difficult to explain briefly (I spent about a year
|
|
explaining it to customers of the Norton Backup). Think of
|
|
it this way:
|
|
|
|
<p> If you have a full -- you can just restore that.
|
|
|
|
<p> If you have a full, and a series of differentials,
|
|
you can restore the most recent full, and the
|
|
most recent differential (any older fulls or differentials
|
|
are unneeded)
|
|
|
|
<p> If you have a full and a series of incrementals you
|
|
need to restore the most recent full, and each
|
|
subsequent incremental -- in order until the most
|
|
Recent.
|
|
|
|
<p> It's possible (even sensible in some cases) to use a
|
|
hybrid of all three methods. Let's say you have a large
|
|
server that takes all day and a rack full of tapes to do a
|
|
full backup. You might be able to do differentials for
|
|
a week or two on a single tape per night. When that fills
|
|
up you might do an incremental, and then go back to
|
|
differentials. Doing this to a maximum of three incrementals
|
|
might keep your all day backup marathons down to once a month.
|
|
The restore must go through the "hierarchy" of media in the
|
|
correct order -- most recent full, each subsequent incremental
|
|
in order, and finally the most recent differential that was
|
|
done after that.
|
|
|
|
<p> (Personally, I avoid such complicated arrangements like the
|
|
plague. However they are necessary in some sites.)
|
|
|
|
|
|
|
|
<P>
|
|
-- Jim
|
|
|
|
<!--================================================================-->
|
|
<P> <hr> <P>
|
|
<center><H4>Previous "Answer Guy" Columns</H4></center>
|
|
<P>
|
|
<A HREF="../issue13/answer.html">Answer Guy #1, January 1997</A><BR>
|
|
<A HREF="../issue14/answer.html">Answer Guy #2, February 1997</A><br>
|
|
<A HREF="../issue15/answer.html">Answer Guy #3, March 1997</A><br>
|
|
<A HREF="../issue16/answer.html">Answer Guy #4, April 1997</A>
|
|
<P><HR><P>
|
|
<center><H5>Copyright © 1997, James T. Dennis <BR>
|
|
Published in Issue 17 of the Linux Gazette May 1997</H5></center>
|
|
|
|
<P> <hr> <P>
|
|
<!--================================================================-->
|
|
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