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<H1><A NAME="answer">
<img src="../gx/dennis/qbubble.gif" alt="(?)"
border="0" align="middle">
<font color="#B03060">The Answer Gang</font>
<img src="../gx/dennis/bbubble.gif" alt="(!)"
border="0" align="middle">
</A></H1>
<BR>
<H4>By Jim Dennis, Ben Okopnik, Dan Wilder, Dustin Puryear, Anthony Greene,
Brian Finn, Richard Turner, the Editors of <em>Linux Gazette</em>...
and You!
<br>Send questions (or interesting answers) to
<a href="mailto:linux-questions-only@ssc.com">linux-questions-only@ssc.com</a>
</H4>
</center>
<p><hr><p>
<!-- endcut ======================================================= -->
<H3>Contents:</H3>
<dl>
<dt><a href="#tag/greeting"
><strong>&para;: Greetings From Heather Stern</strong></A></dl>
<DL>
<!-- index_text begins -->
<dt><A HREF="#tag/1"
><img src="../gx/dennis/qbub.gif" height="28" width="50"
alt="(?)" border="0"
><strong>Linux Gazette</strong></a>
<dt><A HREF="#tag/2"
><img src="../gx/dennis/qbub.gif" height="28" width="50"
alt="(?)" border="0"
><strong>table overflow</strong></a>
<dt><A HREF="#tag/3"
><img src="../gx/dennis/qbub.gif" height="28" width="50"
alt="(?)" border="0"
><strong>Sed / Awk Script</strong></a>
<dt><A HREF="#tag/4"
><img src="../gx/dennis/qbub.gif" height="28" width="50"
alt="(?)" border="0"
><strong>Porting to Access</strong></a>
<dt><A HREF="#tag/5"
><img src="../gx/dennis/qbub.gif" height="28" width="50"
alt="(?)" border="0"
><strong>Issues with a modem</strong></a>
<dt><A HREF="#tag/6"
><img src="../gx/dennis/qbub.gif" height="28" width="50"
alt="(?)" border="0"
><strong>LinuxRedHat Errno 404</strong></a>
<dt><A HREF="#tag/7"
><img src="../gx/dennis/qbub.gif" height="28" width="50"
alt="(?)" border="0"
><strong>IP Masq and X</strong></a>
<dt><A HREF="#tag/8"
><img src="../gx/dennis/qbub.gif" height="28" width="50"
alt="(?)" border="0"
><strong>extra keyboard keys under X</strong></a>
<dt><A HREF="#tag/9"
><img src="../gx/dennis/qbub.gif" height="28" width="50"
alt="(?)" border="0"
><strong>cloning with dd</strong></a>
<dt><A HREF="#tag/10"
><img src="../gx/dennis/bbub.gif" height="28" width="50"
alt="(!)" border="0"
><strong>`HELP: Crontab not running</strong></a>
<dt><A HREF="#tag/11"
><img src="../gx/dennis/qbub.gif" height="28" width="50"
alt="(?)" border="0"
><strong>Replacing an MS Exchange Mail Server with Linux</strong></a>
<dt><A HREF="#tag/13"
><img src="../gx/dennis/qbub.gif" height="28" width="50"
alt="(?)" border="0"
><strong>background processes in Linux</strong></a>
<dt><A HREF="#tag/16"
><img src="../gx/dennis/qbub.gif" height="28" width="50"
alt="(?)" border="0"
></a>serial consoles, install, boot, etc --or--
<dd><A HREF="#tag/16"
><strong>Serial Consoles</strong></a>
<dt><A HREF="#tag/17"
><img src="../gx/dennis/qbub.gif" height="28" width="50"
alt="(?)" border="0"
></a>Confused About Internet Access to My Home Computer --or--
<dd><A HREF="#tag/17"
><strong>Does Internet access require an ISP?</strong></a>
<!-- index_text ends -->
</DL>
<!-- .~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~. -->
<A NAME="tag/greeting"><HR WIDTH="75%" ALIGN="center"></A>
<H3 align="left"><img src="../gx/dennis/hbubble.gif"
height="50" width="60" alt="(&para;) " border="0"
>Greetings from Heather Stern</H3>
<!-- begin hgreeting -->
Well, it's autumn at last, and sunny but cold and windy days (with the
leaves fluttering around ... heh, that would make a great backdrop on
my wallpaper...) are in competition with fluffy grey cloudy days (which
I also like). I'm pretty pleased; the Gang is growing!
<p>
The flip side of that is, I didn't get quite everything in. Some of the
items might well become seperate articles. Others will be seen next
month.
<p>
Anyways, I wanted to babble just a little bit about themes. Nowadays
your computer does not have to be drab and boring. Or, it <em>can</em>
be plain - but <em>your</em> idea of comfortably plain. With the fancier
window managers you hardly have to be sure that windows under X are still
square.
<p>
So, what did your computer dress like for All Hallow's Eve? Mine wants
to go as a Tektronix vector terminal, and the best I could find it was
a copy of Spacewars...
<p>
See you next month, everyone!
<!-- end hgreeting -->
<!-- .~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~. -->
<A NAME="tag/1"><HR WIDTH="75%" ALIGN="center"></A>
<!-- begin 1 -->
<H3 align="left"><img src="../gx/dennis/qbubble.gif"
height="50" width="60" alt="(?) " border="0"
>Linux Gazette</H3>
<p><strong>From <EM>Ben Okopnik</EM> to Jon Lapham on Thu, 5 Oct 2000
</strong></p>
<P><STRONG>
If I read your article correctly, you used sendmail to change your
"From" header and add some aliases. Why did you use sendmail to do
this? Why not set all this up in your email client? As a fellow mutt
enthusiast, you do know that this can be configured in your .muttrc and
that you can set up a global ".muttrc" for the system? It seems to me
that you should try to make it easy for your brother to do things like add
a new alias to his email list. The sendmail alias solution seems a bit
overkill IMO.
</STRONG></P>
<BLOCKQUOTE><IMG SRC="../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
I see that I've failed to explain my requirements sufficiently... &lt;grin&gt; I swear, LG readers are the best literary critics in the world!
</BLOCKQUOTE>
<BLOCKQUOTE>
Changing the <TT>/etc/Muttrc</TT> or the ~/.muttrc only changes the "From:" (note the colon), and not the "From " header (which does not exist at the time that the e-mail is created; it is added by the MTA). A number of mail readers, including Netscape (at this point, having done some serious fiddling with Muttrc, I'm uncertain about Mutt), use the "From " header in forming their 'Received from' and 'On dd/dd/dd, &lt;user&gt; wrote:' lines; since I get quite a lot of mail from other Linux users, I see a lot of "On dd/dd/dd, root wrote:"... Often (and this is much worse) the sender addy looks normal, but the "Reply to:" is set to "localusername@isp_host.com" <TT>-</TT> if you don't pay attention when you hit "Reply", you'll get an unpleasant surprise in 3-5 days (e.g., "Mail could not be delivered to '<A HREF="mailto:root@geocities.com"
>root@geocities.com</A>'...") In order to fix those headers completely, I change both the .muttrc and the sendmail setup. By the way, I found that in RedHat, the 'send-hook * my_hdr From:' line in Muttrc caused Mutt to give an error message. It works fine on my <A HREF="http://www.debian.org/">Debian</A> boxes...
</BLOCKQUOTE>
<BLOCKQUOTE>
Also, rather than adding <em>aliases</em>, I've caused sendmail to do <em>address conversions</em>, a completely different issue. An alias is a short name used as a substitute for a recipient's mail address; the conversions are a way for sendmail to know that the local username "ben" should be converted to "<A HREF="mailto:fuzzybear@pocketmail.com"
>fuzzybear@pocketmail.com</A>" on all outgoing mail.
</BLOCKQUOTE>
<P><STRONG><IMG SRC="../gx/dennis/qbub.gif" ALT="(?)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
I install RH linux on peoples machines all the time, and I have to say I
almost never have to change the default sendmail setup, even for single
user systems connected via ISP.
</STRONG></P>
<BLOCKQUOTE><IMG SRC="../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
Try this: once you've set up one of those accounts, send mail to yourself (not the local username, but the mail account at your ISP) and read the headers. You'll most likely find that the "From " header has your local username instead of your e-mail address. Of course, if you've found a way to fix this via Muttrc, I would be more than happy to learn it!
</BLOCKQUOTE>
<BLOCKQUOTE>
Ben Okopnik
</BLOCKQUOTE>
<!-- sig -->
<!-- end 1 -->
<!-- .~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~. -->
<A NAME="tag/2"><HR WIDTH="75%" ALIGN="center"></A>
<!-- begin 2 -->
<H3 align="left"><img src="../gx/dennis/qbubble.gif"
height="50" width="60" alt="(?) " border="0"
>table overflow</H3>
<p><strong>From <em>Heather Stern</em> and <em>Jim Dennis</em> to
james zhuang on Fri, 6 Oct 2000
</strong></p>
<P><STRONG>
Hi,
</STRONG></P>
<P><STRONG>
I am runing Redhat Linux 6.x. Recently I am getting an error message
'neighbour table overflow' pop up in the console screen.
</STRONG></P>
<P><STRONG>
Any ideas,
<br>James
</STRONG></P>
<BLOCKQUOTE><IMG SRC="../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>[Heather]
Yes, it means your localhost interface is not set up correctly. I don't
know the actual mechanics (perhaps one of the rest of the Gang will chime
in) but basically, the message is about your ARP cache going crazy trying
to deal with what is really local traffic.
</BLOCKQUOTE>
<BLOCKQUOTE>
Until you fix it, session based protocols like samba, nfs, ftp and telnet,
and ssh will have iffy connections. Samba and NFS will probably be so
annoying you can't really use them; a good ftp client will just feel like
it's slow as molasses.
</BLOCKQUOTE>
<BLOCKQUOTE>
Whereas, if you go into <TT>/etc/sysconfig/network-scripts</TT> and you make sure
that you have a valid ifcfg-lo file, things will be properly speedy.
</BLOCKQUOTE>
<BLOCKQUOTE><IMG SRC="../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>[JimD]
I noticed that 'pump' and some other DHCP clients would corrupt
your localhost/loopback configuration and remove the routes thereto
unless you explicity tell them which interface you want them to
work on. You'd think that 'pump' et al would default to leaving
your lo interface alone <TT>---</TT> but that seemed to be where I was
getting it for awhile.
</BLOCKQUOTE>
<!-- sig -->
<!-- end 2 -->
<!-- .~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~. -->
<A NAME="tag/3"><HR WIDTH="75%" ALIGN="center"></A>
<!-- begin 3 -->
<H3 align="left"><img src="../gx/dennis/qbubble.gif"
height="50" width="60" alt="(?) " border="0"
>Sed / Awk Script</H3>
<p><strong>From <em>Dan Wilder</em> to Kopf on Sat, 14 Oct 2000
</strong></p>
<P><STRONG>
Could someone tell me how to write a sed script which'll put text at the
beginning of each line of a file, and change all the backslashes in the file to
forwardslashes?
</STRONG></P>
<P><STRONG>
I need it so that I can change all my .m3u files from windows format to UNIX,
IE from:
</STRONG></P>
<P><STRONG><BLOCKQuote>
Deftones\White Pony\Pink Maggit.mp3
</BLOCKQuote></STRONG></P>
<P><STRONG>
to
</STRONG></P>
<P><STRONG>
<TT>/mnt/win_c/mp3s/Deftones/White</TT> Pony/Pink Maggit.mp3
</STRONG></P>
<P><STRONG>
Anyone have any ideas?
</STRONG></P>
<BLOCKQUOTE><IMG SRC="../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
Haven't tried it, but
</BLOCKQUOTE>
<BLOCKQUOTE><BLOCKQUOTE><CODE>
#!/bin/sh
<BR>#
<BR># call with filename as first argument. Puts
<BR># out revised file to standard out
</CODE></BLOCKQUOTE></BLOCKQUOTE>
<BLOCKQUOTE><BLOCKQUOTE><CODE>
sed 's%\%/%g;s%^%/mnt/win_c/mp3s/%' $1
</CODE></BLOCKQUOTE></BLOCKQUOTE>
<BLOCKQUOTE>
Uses "%" as delimiter, to avoid having to escape the
more conventional forward slash. The
</BLOCKQUOTE>
<BLOCKQUOTE>
s%\%/%g
</BLOCKQUOTE>
<BLOCKQUOTE>
says to put a forward slash in place of a backslash, and
the "g" modifier says to do it for every such.
</BLOCKQUOTE>
<BLOCKQUOTE>
;
</BLOCKQUOTE>
<BLOCKQUOTE>
is a command delimiter
</BLOCKQUOTE>
<BLOCKQUOTE>
s%^%/mnt/win_c/mp3s/%
</BLOCKQUOTE>
<BLOCKQUOTE>
says to substitute <TT>/mnt...</TT> at the beginning of each line
(that's what "^" matches).
</BLOCKQUOTE>
<BLOCKQUOTE>
For more info, see "man sed". This manpage contains one
of the several fine introductions to regular expressions,
which have the ability to match things like the beginning
or ending of a line, strings containing not just particular
characters put particular sets of characters, and so on.
See also "man grep".
</BLOCKQUOTE>
<!-- sig -->
<p><em>... but, when Kopf tried it ...</em></p>
<!-- end 3 -->
<P><STRONG><IMG SRC="../gx/dennis/qbub.gif" ALT="(?)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
Hi Dan,
</STRONG></P>
<P><STRONG>
I entered that in, but it gives me an error of:
</STRONG></P>
<P><STRONG><BLOCKQuote>
sed: <TT>-e</TT> expression #1, char 11: Unknown option to 's'
</BLOCKQuote></STRONG></P>
<P><STRONG>
I don't know what char 11 is, is it the 11th character inside the quotes of
what's being sent to sed? I've been messing around with the script, but to no
avail...
</STRONG></P>
<P><STRONG>
Any Ideas?
</STRONG></P>
<P><STRONG>
Thanks,
</STRONG></P>
<P><STRONG>
Aengus
</STRONG></P>
<BLOCKQUOTE><IMG SRC="../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>Try
</BLOCKQUOTE>
<BLOCKQUOTE><BLOCKQUOTE><CODE>
sed 's%\\%/%g;s%^%/mnt/win_c/mp3s/%'
</CODE></BLOCKQUOTE></BLOCKQUOTE>
<BLOCKQUOTE>
The "\" has special significance as an escape character,
means "ignore me but take next character literally".
</BLOCKQUOTE>
<BLOCKQUOTE>
My bad.
</BLOCKQUOTE>
<!-- sig -->
<!-- end 3 -->
<!-- .~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~. -->
<A NAME="tag/4"><HR WIDTH="75%" ALIGN="center"></A>
<!-- begin 4 -->
<H3 align="left"><img src="../gx/dennis/qbubble.gif"
height="50" width="60" alt="(?) " border="0"
>Porting to Access</H3>
<p><strong>From <em>Ben Okopnik</em> to John Humphre Halliday on Tue, 17 Oct 2000
</strong></p>
<p><strong>
Hello Answer Guy!
</strong></p>
<BLOCKQUOTE><IMG SRC="../gx/dennis/qbub.gif" ALT="(?)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
Hello, John -
</BLOCKQUOTE>
<BLOCKQUOTE>
The Answer Guy/Gang is a column in the Linux Gazette; we answer Linux-based questions for our readers. It just so happens, though, that I was the EDP manager for an insurance company in the Virgin Islands <TT>-</TT> and this company used Clipper (all the in-house apps were written in it). Due to the major Y2K issues inherent in their operations, I convinced them to switch to a different suite of apps <TT>-</TT> which involved converting the old databases to Access.
</BLOCKQUOTE>
<BLOCKQUOTE>
First, for the Linux community: for those of you who want to read/use Clipper DBFs under Linux, I've written a front end for Martin Schulze's "dbview" called "clipview"; it's a viewer/converter that patches the differences between the two formats. It's available on my site <TT>-</TT> <A HREF="http://www.geocities.com/~ben-fuzzybear/clipview.tgz"
>http://www.geocities.com/~ben-fuzzybear/clipview.tgz</A> <TT>-</TT> and Martin may also be including the functionality in future releases of "dbview".
</BLOCKQUOTE>
<P><STRONG><IMG SRC="../gx/dennis/qbub.gif" ALT="(?)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
I was hoping you'd be able to recommend the quickest way to port from a
Clipper/DB2 database to Access 2000. A client has asked that I do this for
them and I know almost nothing about Clipper <TT>-</TT> just that it's a compiler for
DB2 type databases (.dbf). Is it possible to access the tables through an
ODBC connection in Access and simply copy/import the tables/data to Access?
</STRONG></P>
<BLOCKQUOTE><IMG SRC="../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
You actually have several ways to do it; Access can link the files via ODBC or read them via its "import" facility (DB3, DB4, or FoxPro types work fine; I seem to remember DB2 as not working correctly...) Note that linking works fine unless you specify "shared" mode; then, it becomes dead slow. If you decide to import the files, make absolutely sure that you index them beforehand; Access can make a really horrible mess of a file that is out of index, and will do so without any notification... By the same token, double-check any files you import (# of records, totals, etc.)
</BLOCKQUOTE>
<BLOCKQUOTE>
Good luck!
<br>Ben Okopnik
</BLOCKQUOTE>
<!-- sig -->
<!-- end 4 -->
<!-- .~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~. -->
<A NAME="tag/5"><HR WIDTH="75%" ALIGN="center"></A>
<!-- begin 5 -->
<H3 align="left"><img src="../gx/dennis/qbubble.gif"
height="50" width="60" alt="(?) " border="0"
>Issues with a modem</H3>
<p><strong>From <em>Ben Okopnik</em> to J. Miguel Iglesias S. on Wed, 18 Oct 2000
</strong></p>
<P><STRONG>
I have a PC running RedHat 6.2, I also have an
internal Motorola ModemSurfr 56k.
</STRONG></P>
<P><STRONG>
Some guy told me he found the way to make it work with
linux, so he told me to define the parameters using
the setserial function.
</STRONG></P>
<BLOCKQUOTE><IMG SRC="../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
Just for the sake of clarity: "setserial" is used to configure the serial port, which is necessary for access to the modem; it does not configure the modem itself. In the case of internal modems such as yours, the port is part of the card itself <TT>-</TT> but you should still realize that there is a difference.
</BLOCKQUOTE>
<P><STRONG><IMG SRC="../gx/dennis/qbub.gif" ALT="(?)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
Checking the boot log I saw the system runs setserial
at boot and detects the port for the modem.
</STRONG></P>
<BLOCKQUOTE><IMG SRC="../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
That's pretty standard, at least in the distributions with which I'm familiar; the problem is that the values to which the ports are set are usually 'auto' or default values. It pays to manually configure "setserial" to get the best performance (and in some cases, _any_ performance) from your serial ports: after a bit of tweaking, I saw the data transfer rate across my serial link go from just over 9kB/s to just under 12kB/s.
</BLOCKQUOTE>
<P><STRONG><IMG SRC="../gx/dennis/qbub.gif" ALT="(?)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
However I used the setserial function and somehow my
modem gave me some response using minicom.
</STRONG></P>
<BLOCKQUOTE><IMG SRC="../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
A good sign! This says that your modem is _not_ a Winmodem, and you're talking to the right port.
</BLOCKQUOTE>
<P><STRONG><IMG SRC="../gx/dennis/qbub.gif" ALT="(?)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
If I use minicom, I'm able to dial to my ISP, but the
speed is way too slow (it takes about 30 seconds just
to display the greeting from my ISP) so my connection
times out before I'm able to login to the ISP.
</STRONG></P>
<BLOCKQUOTE><IMG SRC="../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
This sounds like a conflict <TT>-</TT> and in this term, I include hardware as well as software that sets up hardware, such as "setserial". Let's go over the possibilities.
</BLOCKQUOTE>
<BLOCKQUOTE>
1) Serial port. As a guess, I would say that this is most likely the culprit, given that tweaking "setserial" is what allowed you to see your modem in the first place. Read the "setserial" man page carefully, particularly paying attention to the speed flags such as "hi" and "vhi". Check the other settings for the port you're using, port and IRQ both, and _specify_ them rather than auto-configuring. "setserial" can be used right from the command line, so you do not have to reboot to change the settings; experiment with different values and see if they produce any changes.
</BLOCKQUOTE>
<BLOCKQUOTE>
2) "Usage" conflict. In theory, once some piece of software uses a given serial port, it will write a "lock" file that will prevent other software from trying to use it. Unfortunately, this scheme is not perfect: a particularly stupid piece of software (one that does not honor or check for the lock), or one that uses the 'cua' port addressing scheme (as in '<TT>/dev/cua0</TT>', etc.) may try to use a port that is already in use, causing a problem. Immediately after rebooting and _before_ trying to do anything with the modem, try running the "fuser" utility on the appropriate "<TT>/dev/ttySx</TT>" port <TT>-</TT> if another process is using it, "fuser" should let you know.
</BLOCKQUOTE>
<BLOCKQUOTE>
3) IRQ conflict. I've noticed that under Linux, as contrasted against DOS/Win, IRQ conflicts seem to slow down the associated process instead of just crashing the machine; a "friendlier" response, as I see it, and certainly easier to diagnose. Try removing the modem from the system and checking "<TT>/proc/interrupts</TT>" for other hardware using the IRQ that it requires (e.g., IRQ4 for ttyS0/ttyS2, or IRQ3 for ttyS1/ttyS3.) Also, check "<TT>/proc/ioports</TT>" for 03F8, 02F8, 03E8, and 02E8 <TT>-</TT> the port addresses for ttyS[0123] <TT>-</TT> though I wouldn't expect too much trouble there.
</BLOCKQUOTE>
<P><STRONG><IMG SRC="../gx/dennis/qbub.gif" ALT="(?)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
If I use the pppdial in Gnome it simply don't detect
my modem.
</STRONG></P>
<BLOCKQUOTE><IMG SRC="../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
I would first make sure that the serial port and the modem were working OK before trying to set up a dial-up account <TT>-</TT> i.e., eliminate the conflicts and make a good connection via "minicom" (make sure you're using the correct setup values in "minicom", as well!), _then_ worry about automating the dial-up.
</BLOCKQUOTE>
<BLOCKQUOTE>
Good luck,
<br>Ben Okopnik
</BLOCKQUOTE>
<!-- sig -->
<!-- end 5 -->
<p><em>... Miguel replies...</em></p>
<!-- begin 5 -->
<P><STRONG><IMG SRC="../gx/dennis/qbub.gif" ALT="(?)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
I will try all your hints and let you know how it worked, maybe my
experience will bring some hope with this modem to other users.
</STRONG></P>
<P><STRONG>
I'm considering to buy an external modem anyway (but still want to make my
current modem as well), do you think I should buy a CNet ($70) or I should
go safer and buy an US Robotics ($110)?
</STRONG></P>
<P><STRONG>
Thanks a lot for all your help and regards
</STRONG></P>
<P><STRONG>
Miguel
</STRONG></P>
<BLOCKQUOTE><IMG SRC="../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
My experience with modems is that "you get what you pay for". I've had
excellent luck with USR and Hayes modems, variable with other brands;
given the above choices, I would certainly plunk down the extra money
for the USR.
</BLOCKQUOTE>
<BLOCKQUOTE>
Along with LinuxMafia's Rick Moen, I believe that internal modems, when
ground fine and lightly roasted, make a decent coffee but have little
use otherwise; making your existing modem work is good troubleshooting
practice, but your idea of replacing it with an external is a good one.
</BLOCKQUOTE>
<BLOCKQUOTE>
Ben Okopnik, modem curmudgeon
<IMG SRC="../gx/dennis/smily.gif" ALT=":)"
height="24" width="20" align="middle">
</BLOCKQUOTE>
<!-- sig -->
<!-- end 5 -->
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<A NAME="tag/6"><HR WIDTH="75%" ALIGN="center"></A>
<!-- begin 6 -->
<H3 align="left"><img src="../gx/dennis/qbubble.gif"
height="50" width="60" alt="(?) " border="0"
>LinuxRedHat Errno 404</H3>
<p><strong>From <em>Heather Stern</em> to Ken on Wed, 18 Oct 2000
</strong></p>
<P><STRONG>
I want to change the default of Errno 404, so that the user is
redirected
to another URL when they request a URL that is not on my server.
What directory and file do I need to edit?
</STRONG></P>
<BLOCKQUOTE><IMG SRC="../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
In most web servers it's possible to configure it so 404 errors
(or other numbered errors, another popular one to force this way
is 501 as it sometimes happens from broken scripts) go to a special
page of your choice. A lot of big ISPs have 404 errors lead to a
front page for their search engine, explaining that whatever you
were trying to find has moved.
</BLOCKQUOTE>
<BLOCKQUOTE>
On <A HREF="http://www.apache.org/">Apache</A> under <A HREF="http://www.suse.com/">SuSE</A>, the file to adjust is <TT>/etc/httpd/httpd.conf</TT>
but it could as easily be under a home directory for Apache under
<TT>/usr</TT> somewhere. I've no experience with the other servers, but the
powerful ones like Roxen Challenger and aolserver should definitely
also have the feature available.
</BLOCKQUOTE>
<!-- sig -->
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<A NAME="tag/7"><HR WIDTH="75%" ALIGN="center"></A>
<!-- begin 7 -->
<H3 align="left"><img src="../gx/dennis/qbubble.gif"
height="50" width="60" alt="(?) " border="0"
>IP Masq and X</H3>
<p><strong>From <em>Heather Stern</em> to M.K. Laha on Thu, 19 Oct 2000
</strong></p>
<P><STRONG>
My Linux PC is on a private LAN that connects to the internet through a
(Linux based) router using IP masquerading.
</STRONG></P>
<P><STRONG>
My problem is that I can't seem to point the
DISPLAY environment variable on a remote machine on the internet to that
of my Linux PC. So, if I run, say, gnuplot, on the remote server, I
cannot see its output on my PC.
</STRONG></P>
<P><STRONG>
I've tried setting the DISPLAY variable on the remote machine to point
to the router but that doesn't work. Seeting the DISPLAY variable to
point to my PC obviously doesn't work because it is not "visible" to the
remote machine on the internet.
</STRONG></P>
<P><STRONG>
I shall greatly appreciate any help/pointers. Thanks in advance.
</STRONG></P>
<P><STRONG>
<TT>-</TT> Manas Laha
</STRONG></P>
<BLOCKQUOTE><IMG SRC="../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
So assuming that you are at one Linux box (Home) and your other Linux box
(Work) is behind all this firewall stuff. (Yours might really have some
other relationship to you, but this will help everyone understand what
I mean, and usually it's corporate boxes that have better defenses.)
</BLOCKQUOTE>
<BLOCKQUOTE>
If you have been provided a way to reach Work from Home via ssh, then all
you need to do is turn on X11 forwarding. Then ssh will create a "virtual"
display (usually Work:10.0) which will acept X GUI commands, but really
send them up the ssh pipe back to Home.
</BLOCKQUOTE>
<BLOCKQUOTE>
So, ot's okay not to be running X on the Work system at all, as long as the
libraries are there so programs that you want to run can be good X clients.
You do need to be running X on your Home system though. Launch ssh out of
an xterm (eterm, etc.) and both your ssh client plus Work's ssh daemon must
be given the options that X11 forwarding is okay. Why? Because these days
it usually defaults to off, as it's a security risk; X usally has an
annoyingly strong root privilege. You can reduce the risk by using .Xauthority
files so only <EM>your</EM> account at Work can use the pipe.
</BLOCKQUOTE>
<BLOCKQUOTE>
What most people don't think of, is that this trick, where Work's CPU is
supposed to display on Home's monitor, used to be the normal way that the
X windowing system was used... and that's why the part of X that paints on
the monitor is called the server.
</BLOCKQUOTE>
<!-- sig -->
<!-- end 7 -->
<p><em>... Manas answers...</em></p>
<!-- begin 7 -->
<p><strong><IMG SRC="../gx/dennis/qbub.gif" ALT="(?)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
Thanks for your prompt reply. I haven't tried using ssh so far, but
I shall certainly try it out now.
</strong></p>
<p><strong>
<TT>-</TT> Manas Laha
</strong></p>
<!-- end 7 -->
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<A NAME="tag/8"><HR WIDTH="75%" ALIGN="center"></A>
<!-- begin 8 -->
<H3 align="left"><img src="../gx/dennis/qbubble.gif"
height="50" width="60" alt="(?) " border="0"
>extra keyboard keys under X</H3>
<p><strong>From <em>Ben Okopnik</em> to Gavin W. Burris on Sun, 22 Oct 2000
</strong></p>
<P><STRONG><IMG SRC="../gx/dennis/qbub.gif" ALT="(?)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
I have a Gateway keyboard with multimedia keys along the top. Is there
any way to use these under X? Could I press one and have a program or
shell script run? Thank you for your time.
</STRONG></P>
<BLOCKQUOTE><IMG SRC="../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
The answer depends on exactly what those keys do. If they are
"programmable" keys such as Gateway used to have, then their definition
is up to you: if you can invoke a shell script by typing something in,
then you can invoke it with a "programmable" key. As an example,
"icewm" can use those "Windows" keys to pull up the program menu;
a combination of arrow keys and the 'Enter' key will invoke any of the
listed apps. "icewm" can also (I believe this violates the "window
manager mandate", but works very well for me personally) intercept
Ctrl- key combinations, which can then be tied to specific commands.
</BLOCKQUOTE>
<BLOCKQUOTE>
If, on the other hand, they generate some sort of previously unmapped
key codes, then you would have to dig a little deeper into your WM man
page and other reference material. The "key codes must be passed to the
application" directive seems to be one that is ignored by most WMs, and
one or more may be capable of being 'told' to intercept these new
codes <TT>-</TT> but this would obviously be a per-WM-specific feature.
</BLOCKQUOTE>
<BLOCKQUOTE>
I recommend taking a closer look at what's happening via 'showkey' in a
VT and 'xev' in an xterm. Once you have an idea of what keycodes you're
generating, you'll know in what direction to search.
</BLOCKQUOTE>
<BLOCKQUOTE>
Ben Okopnik
</BLOCKQUOTE>
<!-- sig -->
<!-- end 8 -->
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<A NAME="tag/9"><HR WIDTH="75%" ALIGN="center"></A>
<!-- begin 9 -->
<H3 align="left"><img src="../gx/dennis/qbubble.gif"
height="50" width="60" alt="(?) " border="0"
>cloning with dd</H3>
<p><strong>From <em>Ben Okopnik</em> to Chris Smart on Mon, 23 Oct 2000
</strong></p>
<P><STRONG><IMG SRC="../gx/dennis/qbub.gif" ALT="(?)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
Hi, do you know how I can speed up the dd command under Linux when cloning
disks. I use dd if=/dev/hd? of=/dev/hd? at the moment, are there any flags
that I can use to speed it up. Or maybe you know a quicker way to clone
disks that preferably doesn't use Norton ghost or powerquest disk image!
</STRONG></P>
<P><STRONG>
Any help will be much appreciated
</STRONG></P>
<BLOCKQUOTE><IMG SRC="../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
There is a "hard limit" associated with the type of process that you're
talking about: the 'speed', or the maximum data transfer rate of the
slowest HD. One tool that could be useful, especially if you're cloning
to a number of identical drives, is "hdparm" <TT>-</TT> the man page gives a
good "tuning" guide (I got a significant improvement from my laptop HD
performance after playing with it for a bit) which can help you maximize
the DTR of a given drive. This applies to both of the drives involved.
</BLOCKQUOTE>
<BLOCKQUOTE>
The other issue is, of course, "dd" itself, particularly the 'bs'
option which sets the size of the block that is read from 'if' and
written to 'of'. Here is a test worth trying:
</BLOCKQUOTE>
<blockquote><pre>time dd if=/dev/hd? of=testfile bs=[N]k count=M
</pre></blockquote>
<BLOCKQUOTE>
where NxM=10Mbytes, and the source and the target are on different
drives. Vary N (and consequently M) and see what blocksize gives you
the best performance. Given this type of custom-tweaking, I believe you
should be able to improve on the performance of any other software...
</BLOCKQUOTE>
<BLOCKQUOTE>
Ben Okopnik
</BLOCKQUOTE>
<!-- sig -->
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<A NAME="tag/10"><HR WIDTH="75%" ALIGN="center"></A>
<!-- begin 10 -->
<H3 align="left"><img src="../gx/dennis/bbubble.gif"
height="50" width="60" alt="(!) " border="0"
>`HELP: Crontab not running</H3>
<p><strong>From <em>Richard N. Turner</em> on Sat, 09 Sep 2000
</strong></p>
<BLOCKQUOTE>
Dear Editor,
</BLOCKQUOTE>
<BLOCKQUOTE>
I saw the article mentioned in the subject and some of the
followups and had to reply.
</BLOCKQUOTE>
<BLOCKQUOTE>
I've seen more than my share of people cursing cron and saying:
&quot;But the
script runs fine from the command line!&quot;. Pierre Abbat's reply
in the
September issue was right on. Most people will modify the PATH
variable to
include some directories beyond the major ones that get defined
in places like
<TT>/etc/profile</TT> and scripts will fail when they attempt to run some
commands that
rely on this modified PATH.
</BLOCKQUOTE>
<BLOCKQUOTE>
The thing to remember is that cron doesn't run your .profile
when it runs a
script. If you don't explicitly define the full path to a
program run from
within the script it'll fail. So you either have to make sure
your script
contains something like &quot;/home/mydir/devel/bin/prog1&quot; (or
whatever) or amend
the PATH at the top of the script.
</BLOCKQUOTE>
<BLOCKQUOTE>
Another alternative is to just source, depending on your shell,
either .profile
or .bash_profile from within your script (assuming that it
defines PATH and
whatever other environment variables were helping the script run
from the
command line). If you include a line near the top of your
script like:
</BLOCKQUOTE>
<BLOCKQUOTE><BLOCKQUOTE><CODE>
. /home/mydir/.profile
</CODE></BLOCKQUOTE></BLOCKQUOTE>
<BLOCKQUOTE>
or
</BLOCKQUOTE>
<BLOCKQUOTE><BLOCKQUOTE><CODE>
. /home/mydir/.bash_profile
</CODE></BLOCKQUOTE></BLOCKQUOTE>
<BLOCKQUOTE>
all things you usually rely on in your interactive environment
are defined for
your scripts run under cron as well.
</BLOCKQUOTE>
<BLOCKQUOTE>
If you do decide to source your .profile, you might want to
watch for things
that depend on there being a display and/or keyboard
&quot;attached&quot; to the process
running the script. If there isn't, you might see strange error
messages like
&quot;not a typewriter&quot; or &quot;cannot open display :0.0&quot;. I have a
toolbox of
variables and shell functions that I like to use in a file
called
&quot;std_functions&quot; which I source near the beginning of my
interactive
environment setup as well as my scripts. One of the things I
put in
`std_functions' is:
</BLOCKQUOTE>
<blockquote><pre> TRUE="0 -eq 0" #Lets you define Boolean environment
variables and
FALSE="1 -eq 0" #makes scripts easier to read six
months from now.
if [ -t 0 ]
then
INTERACTIVE=${TRUE}
else
INTERACTIVE=${FALSE}
fi
</pre></blockquote>
<BLOCKQUOTE>
The &quot;-t&quot; test returns `true' if stdin (file handle 0) is
associated with a
terminal. Then in your profile, you can do things like run xrdb
using:
</BLOCKQUOTE>
<blockquote><pre> if [ ${INTERACTIVE} ]
then
xrdb -l ~.Xresources
fi
</pre></blockquote>
<BLOCKQUOTE>
and not get weird messages from your cron jobs (The above `if'
block would, of
course, evaluate as false under cron). I tend to keep my
profile arranged so
that any setup that I need for my interactive sessions is
wrapped by an
if-then-fi block. After all, you don't really need to define
aliases and use
them in your shell scripts (Ugh!).
</BLOCKQUOTE>
<BLOCKQUOTE>
Hope this'll help someone...
</BLOCKQUOTE>
<BLOCKQUOTE>
PS: I've somehow missed reading the Gazette for the last couple
of months. It
keeps getting better. Keep up the good work.
</BLOCKQUOTE>
<BLOCKQUOTE>
--
RNT
</BLOCKQUOTE>
<!-- sig -->
<p><em> On behalf of the crew, thanks! We couldn't do it without you!
-- Heather </em></p>
<!-- end 10 -->
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<A NAME="tag/11"><HR WIDTH="75%" ALIGN="center"></A>
<!-- begin 11 -->
<H3 align="left"><img src="../gx/dennis/qbubble.gif"
height="50" width="60" alt="(?) " border="0"
>Replacing an MS Exchange Mail Server with Linux</H3>
<p><strong>From <em>Dustin Puryear</em>, <em>Anthony E. Greene</em>,
and <em>Brian Finn</em> to
hutchins on 11 Sep 00
</strong></p>
<p><em>On this subject, we hear both from the author of a good book
all about it, a serious cross-platform power user, and someone
who simply found something better than Exchange to use in
this fashion.</em></p>
<P><STRONG>
This is a sort of follow on to your discussion in Issue 56 of reasons
not to migrate a Linux mailserver to MS Exchange.
</STRONG></P>
<P><STRONG>
One feature that the MS Exchange Server/Outlook Client (as well as
the Lotus Notes Server/Client) offers is a centralized address book.
</STRONG></P>
<BLOCKQUOTE><IMG SRC="../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>[Dustin]
Dear Jonathan,
</BLOCKQUOTE>
<BLOCKQUOTE>
I read with some dismay your message to Linux Gazette regarding a lack of
"centralized" directory services on Linux. Nothing could be further from the
truth. There are several LDAP servers ready to run on Linux. Better yet,
OpenLDAP, an open-source LDAP server, compiles easily on Linux and can be
integrated with MTA's such as Sendmail and Postfix. In addition, you can
access the directories on OpenLDAP from Netscape or Outlook 98+ easily. In
fact, I have implemented OpenLDAP at my company and it works great!
</BLOCKQUOTE>
<BLOCKQUOTE>
FYI, I cover both Postfix and OpenLDAP in my book, "Integrate Linux Solutions
into Your Windows Network," which is aimed specifically at NT managers wishing
to use Linux to their advantage in NT-dominated networks. (Of course, it works
the other way around as well--if you wish to bring NT/Windows into your UNIX
organization the book just as well.)
</BLOCKQUOTE>
<BLOCKQUOTE>
Feel free to ask me any specific questions that you may have.
</BLOCKQUOTE>
<BLOCKQUOTE>
Best regards, Dustin
</BLOCKQUOTE>
<BLOCKQUOTE>
---
Dustin Puryear
<A HREF="mailto:dpuryear@usa.net"
>dpuryear@usa.net</A>
</BLOCKQUOTE>
<!-- sig -->
<p><em>Hey Dustin, thanks for joining the Gang! If anyone sends you good
questions and you copy your answers to <strong>LG</strong> at
<a href="mailto:linux-questions-only@ssc.com">linux-questions-only@ssc.com</a> -- we will publish
them so more people can understand how it all ticks.
-- Heather </em></p>
<BLOCKQUOTE><IMG SRC="../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>[Anthony]
There is no reason this would not work for external addresses. I run an
LDAP server on my home network for members of my household. Most of the
addresses are for external users. I update it using an LDAP client
&lt;<A HREF="http://www.biot.com/gq/&gt"
>http://www.biot.com/gq/&gt</A>; and the changes are immediately available to everyone.
</BLOCKQUOTE>
<BLOCKQUOTE>
Netscape has no problem using the LDAP server automatically to resolve
partial addresses. I did the same thing in my former organization where Outlook
2000 and Outlook Express were the clients. The Outlook 2000 client needed to
be tweaked to use a more flexible LDAP query, but then they both worked
fine. Even the StarOffice mail client can use LDAP, but the procedure for
selecting addresses in StarMail is tedious and non-intuitive.
</BLOCKQUOTE>
<BLOCKQUOTE>
The Outlook 2000 installer makes you choose either Internet-Only or
Exchange Server mode. If you choose Exchange Server mode (the default, I think),
then you will have to edit the registry to get a more flexible LDAP query. The
default search looks only at the beginning of the email address. It does
not search the 'cn' (commonName), 'sn' (surname), 'givenName', or any other
attributes. I changed the search so that it looked anywhwere in the 'cn'
attribute. You can figure this out by looking at the man pages for the utilities
that ship with OpenLDAP and the registry entry associated with the LDAP
server on the Windows client machine.
</BLOCKQUOTE>
<BLOCKQUOTE>
If you're limited to performing updates from a Winbox, you might look into
ldap-abook &lt;<A HREF="http://sourceforge.net/projects/ldap-abook/"
>http://sourceforge.net/projects/ldap-abook/</A>&gt;. It's a set of perl
scripts and a module that makes it easy to maintain an LDAP address book.
You will probably have to edit the scripts to fit your situation, but it can
work. I found it easier to do batch updates by updating an LDIF file and
re-importing the whole thing during off-peak periods. If you have a large
directory, you'll probably want to get a good LDAP client instead. The utility
programs that come with OpenLDAP are pretty good if you only have command-line
access to the server.
</BLOCKQUOTE>
<!-- sig -->
<BLOCKQUOTE><IMG SRC="../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>[Brian]
In issue 58, an Answer Guy reader was looking for a Linux replacement
for Microsoft Exchange. I believe OpenMail by HP
(<A HREF="http://www.hp.com/go/openmail"
>http://www.hp.com/go/openmail</A>)
could be what he is looking for. Here is a blurb from Info World about it:
</BLOCKQUOTE>
<BLOCKQUOTE><BLOCKQuote>
"Summary: HP OpenMail is an impressive, highly scalable mail server.
One OpenMail server will handle Microsoft Outlook (with scheduling
and calendar), Lotus cc:Mail, Lotus Notes, Microsoft Mail, Web,
and standard e-mail clients.
</BLOCKQuote></BLOCKQUOTE>
<BLOCKQUOTE>
Cost: Free for Red hat Linux servers with up to 50 mailboxes. $41
per mailbox on Linux Servers, $77 per mailbox on other platforms.
</BLOCKQUOTE>
<BLOCKQUOTE>
Platforms: <A HREF="http://www.redhat.com/">Red Hat</A> Linux 6.x;
<br>HP-UX 10.20 or 11.0;
<br>AIX 4.21 or 4.3;
<br>Solaris 2.5.1 to 2.6
</BLOCKQUOTE>
<BLOCKQUOTE>
Hope this helps,
<br>Brian Finn
</BLOCKQUOTE>
<!-- sig -->
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<A NAME="tag/13"><HR WIDTH="75%" ALIGN="center"></A>
<!-- begin 13 -->
<H3 align="left"><img src="../gx/dennis/qbubble.gif"
height="50" width="60" alt="(?) " border="0"
>background processes in Linux</H3>
<p><strong>From <em>Peter Samuelson</em> to Andy Larkum on Sat, 30 Sep 2000
</strong></p>
<BLOCKQUOTE>
Regarding a recent LG Two-Cent Tip--
[Andy Larkum asks LG]
</BLOCKQUOTE>
<P><STRONG><IMG SRC="../gx/dennis/qbub.gif" ALT="(?)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
I have a small query. I want to log into a Linux machine, set a
process running, and log out again, leaving the process running. It
has been suggested that I can do this by simply using 'nohup
command &amp;' but this didn't work, because the process was killed as
soon as I logged out again.
</STRONG></P>
<BLOCKQUOTE><IMG SRC="../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>[Heather responds] <font color="navy"><em>
screen with autodetach mode turned on would work nicely. We use it
here all the time. -- Heather</em></font>
</BLOCKQUOTE>
<BLOCKQUOTE><IMG SRC="../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>[Peter]
What you want is the 'disown' command, a bash builtin. It causes the
shell to detach a background job from the tty and basically forget it
ever existed.
</BLOCKQUOTE>
<BLOCKQUOTE>
This is really useful in loops. Often I want to start 100 jobs in the
background but don't care about stopping them later. So:
</BLOCKQUOTE>
<BLOCKQUOTE><code>
i=0; while [ $i -lt 100 ]; do some_long_job_involving_$i &amp; disown; ((i=i+1)); done
</code></BLOCKQUOTE>
<BLOCKQUOTE>
Note that I use '&amp;' to put each job in the background, then immediately
disown it. That way the job numbers don't accumulate and get in the
way.
</BLOCKQUOTE>
<BLOCKQUOTE>
If you are forced to use a non-bash shell that doesn't support disown,
you can get the same effect by running the background job in a
subshell:
</BLOCKQUOTE>
<BLOCKQUOTE><BLOCKQUOTE><CODE>
sh -c 'some_long_job &amp;'
</CODE></BLOCKQUOTE></BLOCKQUOTE>
<BLOCKQUOTE>
The 'sh' you spawn to run the job exits immediately <TT>--</TT> it's not an
interactive shell so it doesn't bother with th job control crap <TT>--</TT> and
your login shell is none the wiser about some_long_job still going.
</BLOCKQUOTE>
<BLOCKQUOTE>
Peter
</BLOCKQUOTE>
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<A NAME="tag/16"><HR WIDTH="75%" ALIGN="center"></A>
<!-- begin 16 -->
<H3 align="left"><img src="../gx/dennis/qbubble.gif"
height="50" width="60" alt="(?) " border="0"
>Serial Consoles</H3>
<p><strong>From <em>Jim Dennis</em> to Joseph Annino on Sun, 08 Oct 2000
</strong></p>
<!-- ::
Serial Consoles
~~~~~~~~~~~~~~~
:: -->
<P><STRONG>
One thing that is really great about Sun hardware is that you can get rid of
the monitor, mouse, and keyboard all together and do everything from install
the operating system to change EEPROM settings via a serial console. While
Intel hardware was never designed this way, I cannot find much information
about setting up Linux on Intel to approximate this. Is it possible to
install and boot Linux over a serial console? Log-in in this way is easy,
but to be able to completely administer a system the install and boot
functions are critical, especially the Lilo prompt would be nice.
</STRONG></P>
<BLOCKQUOTE><IMG SRC="../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
Note: Linux on Sun and other SPARC hardware supports the serial
console just as you'd expect. Let's try to remember that Linux is
just a "PC UNIX" anymore. I've also used Linux serial console on
PReP (PowerPC Reference Platform) systems.
</BLOCKQUOTE>
<BLOCKQUOTE>
I've heard that some new Intel motherboards include BIOS support
for serial console. However, I haven't seen one of those yet.
</BLOCKQUOTE>
<BLOCKQUOTE>
As to your question. Yes, Linux can support a serial console, and
it can concurrently support the normal PC console (with virtual
consoles) and a serial console.
</BLOCKQUOTE>
<BLOCKQUOTE>
Your first step is to compile your kernel with serial console
support. That's a standard configuration option in the 2.2.x
kernels and it was available as an unofficial patch for years
(since the pre-1.0 days). There is a small text file to explain
this support in <TT>/usr/src/linux/Documentation/serial-console.txt</TT>
(Obviously depends on your kernel version, but it's been there for
awhile so any recent kernel should include it).
</BLOCKQUOTE>
<BLOCKQUOTE>
Next you have to configure LILO by editing the <TT>/etc/lilo.conf.</TT>
There are two parts to this configuration <TT>---</TT> you want to configure
the LILO bootloader itself to include support for prompting and
handling input on the serial port, and you want to add a command
line parameter to the kernel to enable and configure the serial
console support that you had compile into it.
</BLOCKQUOTE>
<BLOCKQUOTE>
So you need a lilo.conf that looks something like:
</BLOCKQUOTE>
<blockquote><pre>boot=/dev/hda2
root=/dev/hda3
install=/boot/boot.b
map=/boot/map
delay=20
prompt
# vvvvvvvvv
serial=0,19200n8
# ^^^^^^^^^
image=/boot/vmlinuz
label=new
read-only
# vvvvvvvvvvvvvvvvv
append="console=ttyS0,19200"
# ^^^^^^^^^^^^^^^^^
</pre></blockquote>
<BLOCKQUOTE>
Note that these different parameters don't have matching
syntax. On the serial= directive (which configures the
LILO boot loader support) we have the port number (without
the ttyS device name prefix) followed by the speed, parity
and data bits. On the append= drive we are passing a
kernel option. The kernel console= option takes the base
name of a device (with the <TT>/dev/</TT> directory name, but with
the ttyS* prefix/device name), and then the port speed.
</BLOCKQUOTE>
<BLOCKQUOTE>
Actually the speed, parity, and bits settings for both
of these use the same format and syntax. So the important
difference is that one (the serial=) takes just a serial port
number while the other takes a device name (ttyS*). The first time
I tried to get LILO working with a serial console I didn't read it
carefully enough and I thought I knew more than the documentation.
It took me a few hours to figure out that I needed to remove the
"ttyS" from my serial= line!
</BLOCKQUOTE>
<BLOCKQUOTE>
Finally, some newer PC motherboards/chipsets have support
for full serial operation. These tend to be the more
expensive keyboards that are designed for rackmount cases
and are particularly handy for co-location servers.
</BLOCKQUOTE>
<!-- sig -->
<!-- end 16 -->
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<A NAME="tag/17"><HR WIDTH="75%" ALIGN="center"></A>
<!-- begin 17 -->
<H3 align="left"><img src="../gx/dennis/qbubble.gif"
height="50" width="60" alt="(?) " border="0"
>Does Internet access require an ISP?</H3>
<p><strong>From <em>Mike Orr</em> to Jeffrey Stephens on Tue, 17 Oct 2000
</strong></p>
<!-- ::
Does Internet access require an ISP?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
:: -->
<P><STRONG><IMG SRC="../gx/dennis/qbub.gif" ALT="(?)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
I'm a bit confused. I was re-reading back issues of Linux Gazette and
came across this answer which you provided in the Sept. 98 column, issue
32. I am running Redhat 6.2 which I configured using the <A HREF="http://www.kde.org/">KDE</A>
workstation option. I understand you to say in the enclosed answer that
no one can access their computer over the internet without making
arrangements with their ISP. Then what's the big deal about securing my
cable connection? Since I haven't made any arrangements with my ISP
your answer would seem to suggest that I am secure. On the other hand,
if someone can break into my machine then I ought
to be able to connect with it myself over the internet without going
through my ISP. Am I missing something here?
</STRONG></P>
<P><STRONG>
Regards,
</STRONG></P>
<P><STRONG>
Jeff Stephens
</STRONG></P>
<BLOCKQUOTE><IMG SRC="../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>[a past reply] <em><font color="navy">
Permission to Set up a Linux Server
</font></em></blockquote>
<em><font color="navy">
<blockquote>
Alright, I finally figured out what you were asking. It took a little
work, though.
</blockquote>
<blockquote>
First note: when you set up a Linux system it defaults to providing
many services. It is already a "server."
</blockquote>
<blockquote>
What you seem to be asking is: "How do I make my server accessible
via the Internet?"
</blockquote>
<blockquote>
As you surmised you would have to make arrangements with some ISP
to have some dedicated (or at least
"dial on demand") connection to the net, or to "co-locate" your
hardware with them.
</blockquote>
</font color="navy">
</em>
<BLOCKQUOTE><IMG SRC="../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>[Mike]
There are several issues here. One is, what the terms "server", "ISP"
and "being connected to the Internet" all mean. Another is, how do the
different types of Internet connections affect how easy it is for a
cracker to break into your computer.
</BLOCKQUOTE>
<BLOCKQUOTE>
If you have Internet access, you are connected to the Internet <EM>through</EM>
an ISP (Internet Service Provider) of some sort. For cable modems, the
cable company normally runs its own ISP that all customers must use.
My DSL provider allows me to use any of several local ISPs instead of
their own. The cableco or telco connects you to your
ISP through some non-Internet means (cable or DSL to the cableco/telco
central office, then ATM or Frame Relay or whatever to the ISP), and
then the ISP takes it from there. Your ISP is your gateway to the
Internet: no gateway, no Internet.
<br>&nbsp;<br>
Being a "server" means your computer runs services which other people
can use. Of course, at the most basic level, all Internet-aware
computers are servers, because Internet is a two-way street, and if
you can ping up other computers, other computers can ping you.
But normally "server" means you're running application-level services:
web, e-mail, ssh, telnet, ftp, etc. that other people can use. And yes,
most Linux distributions come with all these services enabled by
default, and yes, this is a security risk. (See"Linux Security, or
Rather, the Lack Thereof" in last month's News Bytes
(<A HREF="../issue58/lg_bytes58.html#general"
>http://www.linuxgazette.com/issue58/lg_bytes58.html#general</A>).)
You should know which services your computer is running and turn off
those you don't specifically want to offer.
<P> The answer you quoted was from 1998, and things were different back
then. Cable modems and DSL were not common, at least not in the US.
(Although my Canadian friend likes to point out that he had a cable
modem in eastern BC a year before we even heard the term "cable modem".)
Almost everybody used analog modems with dial-up connections. Dial-up
connections are by nature less vulnerable to
attack than cable modems are, because the would-be cracker will find
that your server:
<ol>
<li> may be disconnected right now.
<li> may have a dynamic IP, and of course the cracker must know the machine's
<EM>current</EM> IP (or domain name) in order to sabotage it.
</ol>
To solve problem (1), dial-up users need a 24-hour connection or a "dial
on demand" service. Dial on demand means the ISP will telephone your
computer whenever a packet comes through for it and the link is down.
This requires a special arrangement with the ISP, and your
computer must be configured to answer the phone, and you have to make
sure that nothing else (answering machine, fax machine or person) picks up
the phone first. Most ISPs would not do this, and the few that did
charged big bucks for it.
</BLOCKQUOTE>
<BLOCKQUOTE>
(Note: Linux distributions have the "diald" daemon which does dial-on-demand
in the opposite direction: whenever your computer or internal network
wants to connect outside, it will dial the ISP for you if the connection is
down. But this does not help the problem above, which is <EM>incoming</EM> traffic.)
</BLOCKQUOTE>
<BLOCKQUOTE>
For any kind of 24-hour connection (dedicated modem with separate phone
line, ISDN, Frame Relay, T-1), you would be paying $140-$1000 per month--
out of reach for most individuals. Those of us who have long desired this
are ecstatic that we can now get this service at an affordable rate.
</BLOCKQUOTE>
<BLOCKQUOTE>
To solve problem (2), you need a static IP (one that never changes) or
"dynamic DNS" service. Of course, this affects cable modems as
well. With a cable modem, you may have a dynamic IP (which changes
every time you plug in the modem, and perhaps every few days as well).
This will at least ensure that even if a cracker breaks in, he (or she)
won't be back over the long term, because when he tries to come back,
he'll find himself on a different computer and he'll have to start from
square one determining its configuration. Of course the tradeoff is, if
you wish to run a web server or e-mail server and you have a dynamic IP,
it'll be mighty inconvenient for the public to know your current IP or
domain name.
</BLOCKQUOTE>
<BLOCKQUOTE>
("Dynamic DNS" means the nameserver is set up to allow its configuration
(which IP your domain name points to) to be changed frequently and
conveniently, either by you typing a new number on a web page or by a
script on your computer which sends in the new information.)
</BLOCKQUOTE>
<BLOCKQUOTE>
So yes, people from the outside can crack your computer even if you
haven't made special arrangements with your ISP. <I>Linux Gazette</I> has
published several articles this year on securing your home network, and these
are all recommended reading.
</BLOCKQUOTE>
<!-- sig -->
<!-- end 17 -->
<!-- .~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~. -->
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<P> <hr> </p>
<H5 align="center"><a href="http://www.linuxgazette.com/copying.html"
>Copyright &copy;</a> 2000, James T. Dennis
<BR>Published in <I>Linux Gazette</I> Issue 59 November 2000</H5>
<H6 ALIGN="center">HTML transformation by
<A HREF="mailto:star@tuxtops.com">Heather Stern</a> of
Tuxtops, Inc.,
<A HREF="http://www.tuxtops.com/">http://www.tuxtops.com/</A>
</H6>
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