1257 lines
49 KiB
HTML
1257 lines
49 KiB
HTML
<!--startcut ==============================================-->
|
|
<!-- *** BEGIN HTML header *** -->
|
|
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
|
|
<HTML><HEAD>
|
|
<META HTTP-EQUIV="Content-Language" CONTENT="en-us">
|
|
<META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1">
|
|
<META NAME="generator" CONTENT="lgazmail v1.4G.i">
|
|
<LINK REV="made" href="mailto:%20linux-questions-only@ssc.com%20"><TITLE>More 2 Cent Tips & Tricks LG #92</TITLE></HEAD>
|
|
<BODY BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#0000FF" VLINK="#0000AF"
|
|
ALINK="#FF0000">
|
|
<!-- *** END HTML header *** -->
|
|
<!--endcut ==============================================-->
|
|
|
|
<!--startcut =========================================================-->
|
|
<!-- *** BEGIN navbar *** -->
|
|
<A HREF="lg_mail.html"><< Prev</A> | <A HREF="index.html">TOC</A> | <A HREF="../index.html">Front Page</A> | <A HREF="http://www.linuxgazette.com/cgi-bin/talkback/all.py?site=LG&article=http://www.linuxgazette.com/issue92/lg_tips.html">Talkback</A> | <A HREF="../faq/index.html">FAQ</A> | <A HREF="lg_answer.html">Next >></A>
|
|
<!-- *** END navbar *** -->
|
|
<!--endcut ===========================================================-->
|
|
|
|
<TABLE BORDER><TR><TD WIDTH="200">
|
|
<A HREF="http://www.linuxgazette.com/">
|
|
<IMG ALT="LINUX GAZETTE" SRC="../gx/2002/lglogo_200x41.png"
|
|
WIDTH="200" HEIGHT="41" border="0"></A>
|
|
<BR CLEAR="all">
|
|
<SMALL>...<I>making Linux just a little more fun!</I></SMALL>
|
|
</TD><TD>
|
|
|
|
|
|
<center>
|
|
<BIG><BIG><STRONG><FONT COLOR="maroon">More 2¢ Tips!</FONT></STRONG></BIG></BIG><BR>
|
|
<!-- BEGIN tips -->
|
|
|
|
<STRONG>By <A HREF="mailto:linux-questions-only@ssc.com">The Readers of <i>Linux Gazette</I></A></STRONG></BIG>
|
|
</TD></TR>
|
|
</TABLE>
|
|
<P>
|
|
|
|
<!-- END header -->
|
|
<center><STRONG>See also: The Answer Gang's
|
|
<a href="../tag/kb.html">Knowledge Base</a>
|
|
and the <i>LG</i>
|
|
<a href="http://www.linuxgazette.com/search.html">Search Engine</a></STRONG>
|
|
</center><HR>
|
|
<UL>
|
|
<!-- index_text begins -->
|
|
<li><A HREF="#tips.1"
|
|
><strong>Backup Software: Robustness</strong></a>
|
|
<li><A HREF="#tips.2"
|
|
><strong>can I have Linux on a ThinkPad G40? with WinXP?</strong></a>
|
|
<li><A HREF="#tips.3"
|
|
></a>Re: [Blt-newuser] Request suggestion for ftp server --or--
|
|
<br><A HREF="#tips.3"
|
|
><strong>FTP Daemons (Servers) and Alternatives: Just Say No?</strong></a>
|
|
|
|
<li><A HREF="#tips.4"
|
|
><strong>Pause after running xterm</strong></a>
|
|
<li><A HREF="#tips.5"
|
|
><strong>Tips on PDF conversion</strong></a>
|
|
<li><A HREF="#tips.6"
|
|
><strong>quotas on directories?</strong></a>
|
|
<li><A HREF="#tips.7"
|
|
><strong>What is Reverse DNS?</strong></a>
|
|
<li><A HREF="#tips.8"
|
|
><strong>Subscribe to groups...........pan,Knode.......????</strong></a>
|
|
<li><A HREF="#tips.9"
|
|
><strong>Confused about symantics of "mount -o,async/sync" commands</strong></a>
|
|
<li><A HREF="#tips.10"
|
|
><strong>Linux Journal Weekly News Notes - Tech Tips</strong></a>
|
|
<!-- index_text ends -->
|
|
</UL>
|
|
<!-- .~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~. -->
|
|
<P> <A NAME="tips.1"><HR WIDTH="75%" ALIGN="center"></A> <P>
|
|
<H3><IMG ALIGN=BOTTOM ALT="" SRC="../gx/lil2cent.gif">
|
|
<FONT COLOR="navy">Backup Software: Robustness</FONT></H3>
|
|
Mon, 2 Jun 2003 08:09:29 +1000
|
|
<BR>Nick Coleman (<a href="mailto:linux-questions-only@ssc.com?cc=njpc@ozemail.com.au&subject=%20Re%3A%20%5BLG%2092%5D%202c%20Tips%20%231">njpc from ozemail.com.au</a>)
|
|
|
|
|
|
<P>
|
|
This is a reply to a letter to the Mailbag in the June 2003 issue of
|
|
Linux Gazette,
|
|
<a href="../issue91/lg_mail.html#wanted.1">compressed tape backups</a>
|
|
</P>
|
|
<P><STRONG>
|
|
quite a while back I remember a discussion on compressed tar archives on
|
|
tape and the security risk, i.e. the data would be unrecoverable behind
|
|
the first damaged bit.
|
|
</STRONG></P>
|
|
<P><STRONG>
|
|
Now at that time I knew that bzip2, unlike gzip, is internally a
|
|
blocking algorithm and it should be possible to recover all undamaged
|
|
blocks after the damaged one.
|
|
</STRONG></P>
|
|
<P><STRONG>
|
|
Your correspondent may like to look into afio instead of tar for
|
|
backups. I believe it recovers from errors much better. The mondo
|
|
rescue tool developer uses it.
|
|
</STRONG></P>
|
|
<P><STRONG>
|
|
Regards,
|
|
<BR>Nick Coleman
|
|
</STRONG></P>
|
|
<BLOCKQUOTE>
|
|
[JimD]
|
|
The problems recovering tar files are worst with GNU tar operating on
|
|
gzip'd archives. star (by Joerg Schily, of cdrecord and mkisofs fame)
|
|
cpio, and pax are all better at resynchronizing to the archive headers
|
|
past a point of file corruption than GNU tar.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
afio might very well be better that cpio. I don't know, I neither run
|
|
my own tests nor perused the code.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
In general I'd suggest that added redundancy (both through ECC --
|
|
error correction coding -- and additional separate copies) is the better
|
|
way to make one's backups more robust.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
I've heard that BRU (backup/recovery utility: <A HREF="http://www.tolisgroup.com"
|
|
>http://www.tolisgroup.com</A>
|
|
a commercial product) adds ECC and checksum data to the archive stream
|
|
as it performs backups --- and defaults to verifying the archive
|
|
integrity in a second pass over the data. With cpio, afio, tar, star,
|
|
dump/restore and pax you have to write your own scripts to perform the
|
|
verification pass. (cpio and presumably afio do add checksums, GNU tar
|
|
doesn't, I don't know about the others). So far as I know none of the
|
|
common free tools adds additional ECC redundancy to their archives.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
There is an obscure little utility called 'ras' (redundancy archive
|
|
system) which can be used to create a set of ECC (sum) files to go
|
|
with set of base files and allow one to recover from the loss of a subset
|
|
of base files. This is essentially a utility to manually (and crudely)
|
|
perform the same sort of redundancy operations as a RAID5 subsystem.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
<A HREF="http://www.icewalkers.com/Linux/Software/52890/ras.html"
|
|
>http://www.icewalkers.com/Linux/Software/52890/ras.html</A>
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
However, I should warn that I haven't used this at all much less tried
|
|
to integrate it into any sane backup/recovery scripts!
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
So far the best free backup tool for Linux still seems to be AMANDA
|
|
(<A HREF="http://www.amanda.org"
|
|
>http://www.amanda.org</A> ) though Bacula (<A HREF="http://www.bacula.org"
|
|
>http://www.bacula.org</A> ) seems
|
|
to have a similar and impressive feature set.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
AMANDA still uses native dump and/or GNU tar to actually perform the
|
|
backup. It initiates those processes on each client, aggregates their
|
|
archives on a central server and manages the process of writing them
|
|
out to tapes (optionally using a tape changer).
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
Thus, AMANDA is tape centric and still has the inherent risks of the
|
|
underlying archiver (vendor's dump --- dumpe2fs for Linux, or GNU tar).
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
I think it would be neat if AMANDA or Bacula were integrated with
|
|
ras or some redundancy library in some meaningful way.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
There is an overview of these and other free backup packages for UNIX
|
|
(and Linux) at:
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE><BLOCKQuote>
|
|
<A HREF="http://www.backupcentral.com/free-backup-software2.html"
|
|
>http://www.backupcentral.com/free-backup-software2.html</A>
|
|
</BLOCKQuote></BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
Ultimately you'd want to keep multiple generations of data backups even
|
|
if you knew that you had perfect ECC, redundancy, media, and drives.
|
|
You need this for the same reason you need backups regardless of how
|
|
sophisticated and redundant your RAID array is configured. Because you
|
|
may find that your software or your users corrupt your data, and you
|
|
may need to back off to earlier, known good versions of the data,
|
|
possibly days, weeks, even month after those backups were made.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
(Some forms of corruption can be subtle and insidious).
|
|
</BLOCKQUOTE>
|
|
|
|
<!-- end 1 -->
|
|
<!-- .~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~. -->
|
|
<P> <A NAME="tips.2"><HR WIDTH="75%" ALIGN="center"></A> <P>
|
|
<H3><IMG ALIGN=BOTTOM ALT="" SRC="../gx/lil2cent.gif">
|
|
<FONT COLOR="navy">can I have Linux on a ThinkPad G40? with WinXP?</FONT></H3>
|
|
Thu, 05 Jun 2003 18:35:32 PST
|
|
<BR>borejsza (<a href="mailto:linux-questions-only@ssc.com?cc=linux-questions-only@ssc.com, linux@linux.ucla.edu&cc=borejsza@ucla.edu&subject=%20Re%3A%20%5BLG%2092%5D%202c%20Tips%20%232">borejsza from ucla.edu</a>)
|
|
|
|
|
|
<P><STRONG>
|
|
Hi,
|
|
</STRONG></P>
|
|
<P><STRONG>
|
|
I am about to buy a laptop and am looking for advice as to its
|
|
compatibility with Linux.
|
|
</STRONG></P>
|
|
<P><STRONG>
|
|
I know little about computers (last time I owned one it was a Commodore
|
|
64), and less about Linux, but saw a friend use it, and would like to
|
|
learn how to myself, and gradually move away from Windows. The laptop I
|
|
am thinking of buying is an IBM ThinkPad G40
|
|
(<A HREF="http://www-132.ibm.com/webapp/wcs/stores/servlet/ProductDisplay?productId=8600909&storeId=1&langId=-1&categoryId=2580117&dualCurrId=73&catalogId=-840"
|
|
>http://www-132.ibm.com/webapp/wcs/stores/servlet/ProductDisplay?productId=8600909&storeId=1&langId=-1&categoryId=2580117&dualCurrId=73&catalogId=-840</A>). I think it is a new model, and could not find it anywhere on the
|
|
pages that list hardware that has been already tried out with Linux.
|
|
</STRONG></P>
|
|
<P><STRONG>
|
|
Can anybody confirm that I can partition that laptop between Linux and
|
|
WindowsXP before I blow all my savings on it?
|
|
</STRONG></P>
|
|
<P><STRONG>
|
|
Thanks,
|
|
<BR>Alex
|
|
</STRONG></P>
|
|
|
|
<blockquote><font color="#1F1F1F">You could buy one preloaded from EmperorLinux:
|
|
(<A HREF="http://www.emperorlinux.com/auk.html"
|
|
>http://www.emperorlinux.com/auk.html</A>)
|
|
-- Ben</font></blockquote>
|
|
|
|
<blockquote><font color="#000066">Or they'll preload a dual boot, or can customize. (So this tip is good
|
|
for more than that one model.)
|
|
-- Heather</font></blockquote>
|
|
|
|
<blockquote><font color="#1F1F1F">As far as I'm concerned, IBM-made hardware today should be a sure bet
|
|
for Linux anyway: they've really thrown themselves behind Linux in a big
|
|
way, and I'd be surprised to hear of a laptop they make that can't run
|
|
it. Come to think of it, given the range of hardware that Linux supports
|
|
these days, making a 'top that can't run Linux would be quite a trick in
|
|
the first place.
|
|
-- Ben</font></blockquote>
|
|
<BLOCKQUOTE>
|
|
[jra]
|
|
Now, that's <EM>not</EM> to say that you can <EM>easily</EM> dual-boot XP. There may
|
|
be reinstallation issues, and licensing; I don't know that Partition-*
|
|
or FIPS can safely resize whatever you have loaded without breaking it,
|
|
and you may not have "install" media for XP -- only "recover" media,
|
|
which will <EM>not</EM> let you install on a resized partition.
|
|
</BLOCKQUOTE>
|
|
|
|
<blockquote><font color="#1F1F1F">Missing install media for WinXP isn't relevant to its ability to coexist
|
|
with Linux, but personally, if my vendor "forgot" to include the Other OS
|
|
that I had paid for - I'd demand my real discs, or that they discount the
|
|
box the price of their OS. Given the number of people competing for your
|
|
business in this venue, I have precious little tolerance for that kind of
|
|
ripoff.
|
|
-- Ben</font></blockquote>
|
|
<BLOCKQUOTE>
|
|
[jra]
|
|
I would google for "linux win xp dual boot howto", and see what I got.
|
|
-- jra
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
[Kapil]
|
|
Apparently, the trick is to: (1) Install Linux and resize the NTFS
|
|
partition (2) Boot the recovery CD for XP (3) Interrupt (count 5
|
|
<IMG SRC="../gx/dennis/smily.gif" ALT=":-)"
|
|
height="24" width="20" align="middle">)
|
|
the reinstallation process and run "OS.bat". It seems XP will then
|
|
"just install" on the resized partition.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
This worked with the laptops bought for our Institute. YMMV.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
-- Kapil.
|
|
</BLOCKQUOTE>
|
|
|
|
<!-- end 2 -->
|
|
<!-- .~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~. -->
|
|
<P> <A NAME="tips.3"><HR WIDTH="75%" ALIGN="center"></A> <P>
|
|
<H3><IMG ALIGN=BOTTOM ALT="" SRC="../gx/lil2cent.gif">
|
|
<FONT COLOR="navy">FTP Daemons (Servers) and Alternatives: Just Say No?</FONT></H3>
|
|
Tue, 3 Jun 2003 06:03:09 -0700
|
|
<BR>Jim Dennis (<a href="mailto:linux-questions-only@ssc.com?cc=Blt-newuser@basiclinux.net&cc=jimd@starshine.org&subject=%20Re%3A%20%5BLG%2092%5D%202c%20Tips%20%233">the <em>LG</em> Answer Guy</a>)
|
|
<BR>Question by Dinos Kouroushaklis on the BLT-newuser list (Blt-newuser from basiclinux.net)
|
|
|
|
<!-- ::
|
|
FTP Daemons (Servers) and Alternatives: Just Say No?
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
:: -->
|
|
<P><STRONG>
|
|
Dear list members,
|
|
</STRONG></P>
|
|
<P><STRONG>
|
|
I would like to hear your suggestions for an ftp server.
|
|
</STRONG></P>
|
|
<P><STRONG>
|
|
I would like to replace an existing win2k ftp server with a Linux based one.
|
|
What I am interested in is reliability and ease of management.
|
|
The machine should need only one (maybe more) ethernet card to provide the
|
|
ftp service (except during installation time). The two ethernet cards can
|
|
be use
|
|
one for management and one for the traffic.
|
|
</STRONG></P>
|
|
<P><STRONG>
|
|
The machine will be an Intel Celeron 400 Mhz with 160 (128+32) and
|
|
20 GB hard disk with a public (static) IP address in the DMZ.
|
|
</STRONG></P>
|
|
<P><STRONG>
|
|
Regards
|
|
</STRONG></P>
|
|
<P>
|
|
Just to be contrarian I have to suggest that you seriously consider
|
|
abandoning FTP entirely. HTTP is adequate for simple, lightweight
|
|
anonymous distribution of files (text or binary). scp, sftp (SSH) and
|
|
rsync over ssh are inherently more secure than plain FTP can ever be.
|
|
Your MS-Windows users can get Putty (and pscp, et al.) for free.
|
|
</P>
|
|
<P>
|
|
(Plain, standard FTP will, by dint of the standards, always pass user
|
|
name and password information "in the clear" across the Internet --- those
|
|
exposing these valuable, private tokens to "sniffers"). For some
|
|
purposes BitTorrent can be far more efficient (for widespread, peer
|
|
assisted distribution of files to many concurrent clients, for
|
|
example).
|
|
</P>
|
|
<P>
|
|
SSH, scp, and sftp:
|
|
</P>
|
|
<P><BLOCKQuote>
|
|
<A HREF="http://www.openssh.org"
|
|
>http://www.openssh.org</A>
|
|
</BLOCKQuote></P>
|
|
<P>
|
|
Putty:
|
|
</P>
|
|
<P><BLOCKQuote>
|
|
<A HREF="http://www.chiark.greenend.org.uk/~sgtatham/putty"
|
|
>http://www.chiark.greenend.org.uk/~sgtatham/putty</A>
|
|
</BLOCKQuote></P>
|
|
<P>
|
|
rsync:
|
|
</P>
|
|
<P><BLOCKQuote>
|
|
<A HREF="http://www.samba.org/rsync"
|
|
>http://www.samba.org/rsync</A>
|
|
</BLOCKQuote></P>
|
|
<P><DL><DT>
|
|
BitTorrent:
|
|
<DD><A HREF="http://bitconjurer.org/BitTorrent"
|
|
>http://bitconjurer.org/BitTorrent</A>
|
|
</DL></P>
|
|
<P>
|
|
If you can, just eliminate FTP and direct your users and customers to
|
|
better alternatives.
|
|
</P>
|
|
<P>
|
|
In general the problem with FTP servers is that they run as root
|
|
(at least during the authentication phase, if they support <EM>anything</EM>
|
|
other than anonymous FTP). So FTP daemons have classically been a
|
|
source of vulnerability (as bad as DNS -- BIND/named --- and MTA --
|
|
sendmail --- daemons).
|
|
</P>
|
|
<P>
|
|
With that in mind, vsftpd would probably be my first free choice.
|
|
(<A HREF="http://vsftpd.beasts.org"
|
|
>http://vsftpd.beasts.org</A> )
|
|
</P>
|
|
<P>
|
|
ProFTPd is popular, and has configuration file syntax that's a vaguely
|
|
similar to <A HREF="http://www.apache.org/">Apache</A>/HTML/SGML (I'll leave it for others to judge that
|
|
a feature or bug). However, ProFTPd is complex and has had too many
|
|
security alerts posted against it for my tastes.
|
|
(<A HREF="http://www.proftpd.org"
|
|
>http://www.proftpd.org</A> ).
|
|
</P>
|
|
<P>
|
|
WU-FTPD (for years the default that shipped with most Linux
|
|
distributions) has the worst security track record in the field. I
|
|
wouldn't recommend it, I don't care how many bugs they've patched.
|
|
There comes a time to abandon the codebase and start from scratch.
|
|
There also comes a time when "brand recognition" (the project's name)
|
|
shifts from notoriety to notorious infamy.
|
|
</P>
|
|
<P>
|
|
By contrast, Chris Evans coded vsftpd specifically to be as secure as
|
|
possible. He discussed the design and every pre-release of the code
|
|
extensively on the Linux security auditing mailing list (and in other
|
|
fora devoted to secure programming and coding topics).
|
|
</P>
|
|
<P>
|
|
If you're willing to go with a commercial/shareware package (that's not
|
|
free) I'd suggest that Mike Gleason's ncftpd has been around longer
|
|
than vsftpd and still has a very good track record.
|
|
(<A HREF="http://www.ncftpd.com"
|
|
>http://www.ncftpd.com</A> ). Registration is only $200 (U.S.) per server
|
|
for unlimited concurrent connections ($100 for up to 50 concurrent
|
|
users) and is free for use in educational domains.
|
|
</P>
|
|
<P>
|
|
If there are no objections I'd like to cross-post this to the Linux
|
|
Gazette for publication (names of querents will be sanitized) since
|
|
the question comes up periodically and I like to refresh this answer
|
|
and the URLs.
|
|
</P>
|
|
<P>
|
|
All of this assumes that you have no special needs of your FTP server.
|
|
If you need special features (directory trees restricted by user/group
|
|
info, pluggable authentication support, virtual domain support, etc)
|
|
then you'll have to review these products more carefully. However,
|
|
each of them offers at least some virtual domain/server functionality
|
|
and a mixture of other features.
|
|
</P>
|
|
<BLOCKQUOTE>
|
|
[Dan]
|
|
For a comprehensive annotated list, see:
|
|
<A HREF="http://linuxmafia.com/pub/linux/security/ftp-daemons"
|
|
>http://linuxmafia.com/pub/linux/security/ftp-daemons</A>
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
Everybody's got their favorite, and mine's PURE-ftpd, of which
|
|
Rick Moen of Linuxmafia says on the above page:
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE><BLOCKQuote>
|
|
Seems like a winner.
|
|
</BLOCKQuote></BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
<A HREF="http://sourceforge.net/projects/pureftpd"
|
|
>http://sourceforge.net/projects/pureftpd</A>
|
|
</BLOCKQUOTE>
|
|
|
|
<!-- end 3 -->
|
|
<!-- .~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~. -->
|
|
<P> <A NAME="tips.4"><HR WIDTH="75%" ALIGN="center"></A> <P>
|
|
<H3><IMG ALIGN=BOTTOM ALT="" SRC="../gx/lil2cent.gif">
|
|
<FONT COLOR="navy">Pause after running xterm</FONT></H3>
|
|
Fri, 30 May 2003 20:39:56 -0400
|
|
<BR>Ben Okopnik (<a href="mailto:linux-questions-only@ssc.com?cc=ben@callahans.org&subject=%20Re%3A%20%5BLG%2092%5D%202c%20Tips%20%234">the <em>LG</em> Answer Gang</a>)
|
|
|
|
|
|
|
|
<blockquote><font color="#000066">Okay, so it's a nickel's worth. So there.
|
|
-- Heather</font></blockquote>
|
|
<P>
|
|
Here's a little problem you might run into: you want to run a certain
|
|
program - say, as a Mozilla "Helper application" - which needs to run in
|
|
an xterm. So, you set it up like so:
|
|
</P>
|
|
|
|
<blockquote><pre>xterm -e myprogram -my -options
|
|
</pre></blockquote>
|
|
<P>
|
|
The only problem is, when it comes time to run it, all you see is a
|
|
flash as the xterm appears, then immediately disappears. What happened?
|
|
What error did it print out? Why (this does happen at times) does it
|
|
work when you launch it 'manually' but not from Mozilla?...
|
|
</P>
|
|
<P>
|
|
Here's an easy and useful solution that will require you to hit a key in
|
|
order to exit the xterm after the program has finished running. Note
|
|
that it may fail on tricky command lines (subshell invocations, evals,
|
|
and other shell-specific gadgetry) but should work fine with normal
|
|
commands and their options.
|
|
</P>
|
|
<p align="center">See attached <tt><a href="misc/tips/okopnik.hold.bash.txt">okopnik.hold.bash.txt</a></tt></p>
|
|
<P>
|
|
Invoke it like so:
|
|
</P>
|
|
|
|
<blockquote><pre>xterm -e hold myprogram -my -options
|
|
</pre></blockquote>
|
|
<BLOCKQUOTE>
|
|
[jra]
|
|
Were you actually planning to <EM>answer</EM> those question, Prof?
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
Or are they left as an exercise for the students?
|
|
<IMG SRC="../gx/dennis/smily.gif" ALT=":-)"
|
|
height="24" width="20" align="middle">
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
[Ben]
|
|
The answer is implicit in the solution provided, and will depend on the
|
|
specific program being launched. The implementation, as always, <EM>is</EM>
|
|
left to the student. Giddyap, dammit.
|
|
<IMG SRC="../gx/dennis/smily.gif" ALT=":)"
|
|
height="24" width="20" align="middle">
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
[JimD]
|
|
</BLOCKQUOTE>
|
|
|
|
<blockquote><pre> xterm -e /bin/sh 'myprogram -my -options; read x'
|
|
</pre></blockquote>
|
|
<BLOCKQUOTE>
|
|
... in other words, have a shell execute your program, then read a
|
|
dummy value from the xterm (the xterm process' console/terminal/stdin)
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
The command will run, output will be displayed, you'll get a pause
|
|
where you can type anything you like (also allowing you to scroll
|
|
through the xterm's buffer). When you hit [Enter] the xterm goes away.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
Seems pretty transparent to me. More verbose:
|
|
</BLOCKQUOTE>
|
|
|
|
<blockquote><pre> xterm -e /bin/sh 'myprogram -my -opts; echo "[Enter] when done: ";read x'
|
|
</pre></blockquote>
|
|
<BLOCKQUOTE>
|
|
More elegant, create a two line script:
|
|
</BLOCKQUOTE>
|
|
<p align="center">See attached <tt><a href="misc/tips/jimd.pauseadter.sh.txt">jimd.pauseadter.sh.txt</a></tt></p>
|
|
<BLOCKQUOTE>
|
|
(I'm not really sure we need the eval, but I don't think it'll hurt in
|
|
any case).
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
Now simply:
|
|
</BLOCKQUOTE>
|
|
|
|
<blockquote><pre> xterm -e pauseafter.sh myprogram -my -opts
|
|
</pre></blockquote>
|
|
<BLOCKQUOTE>
|
|
(<TT>/me</TT> shudders at the electrons that got excited by this blatantly
|
|
obvious suggestion).
|
|
</BLOCKQUOTE>
|
|
|
|
<!-- end 4 -->
|
|
<!-- .~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~. -->
|
|
<P> <A NAME="tips.5"><HR WIDTH="75%" ALIGN="center"></A> <P>
|
|
<H3><IMG ALIGN=BOTTOM ALT="" SRC="../gx/lil2cent.gif">
|
|
<FONT COLOR="navy">Tips on PDF conversion</FONT></H3>
|
|
Thu, 12 Jun 2003 12:12:55 +0100 (BST)
|
|
<BR>Mike Martin (<a href="mailto:linux-questions-only@ssc.com?cc=redtuxxx@yahoo.co.uk&subject=%20Re%3A%20%5BLG%2092%5D%202c%20Tips%20%235">the <em>LG</em> Answer Gang</a>)
|
|
|
|
|
|
<P><STRONG>
|
|
Has anyone any ideas on converting PDF's to decent text.
|
|
</STRONG></P>
|
|
<P><STRONG>
|
|
To explain
|
|
</STRONG></P>
|
|
<P><STRONG>
|
|
I have a document which has been scanned in, with the only accurate
|
|
conversion being to pdf (no images)
|
|
</STRONG></P>
|
|
<P><STRONG>
|
|
So I have used pdf2ps which gives me ps file.
|
|
</STRONG></P>
|
|
<P><STRONG>
|
|
However then when I use psto... anything text like, the output is
|
|
exactly ^L
|
|
</STRONG></P>
|
|
<P><STRONG>
|
|
Any ideas/tips?
|
|
</STRONG></P>
|
|
<BLOCKQUOTE>
|
|
[Thomas]
|
|
If you could convert the pdf to ps and then to LateX then you won't have a
|
|
problem since tex -> ascii is not a problem. However, going from ps to
|
|
ascii might require some more thought.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
I know that there is a utility called "a2ps" which takes ascii and
|
|
converts it to a ps file, however I cannot see a converse one program.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
I am sure that there is a perl module (hey, Ben!) that could be used to
|
|
write a perl-script for such a task, however, I am going to suggest you
|
|
try the following......(I haven't tested this):
|
|
</BLOCKQUOTE>
|
|
|
|
<blockquote><pre>strings ./the_ps_file.ps | col -b > ~/new_text_file.txt
|
|
</pre></blockquote>
|
|
<BLOCKQUOTE>
|
|
I am shunting this through "col" since you describe having lots of "^L"
|
|
characters. You might have to edit the file by hand as well, since I am
|
|
sure that a lot of useless information is being processed.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
[Ben]
|
|
See the "pstotext" utility for that.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
[Andreas]
|
|
There's a utility called pdftotext, it is in the xpdf Package, see the
|
|
xpdf-Homepage
|
|
<A HREF="http://www.foolabs.com/xpdf"
|
|
>http://www.foolabs.com/xpdf</A>
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
Hopefully an OCR has been performed on your scanned document before it
|
|
was converted to pdf, otherwise the pdf file would just contain an image
|
|
and could not directly be converted to text.
|
|
</BLOCKQUOTE>
|
|
<P><STRONG>
|
|
Unfortunately, and very annoyingly this is what seems to have
|
|
happened, seriously aggravating software - it lies.
|
|
</STRONG></P>
|
|
<P><STRONG>
|
|
Off to to see if I can work out how to convert the image to text (its
|
|
only tables)
|
|
</STRONG></P>
|
|
<BLOCKQUOTE>
|
|
[Ben]
|
|
Well, if it's a picture, "pstotext" won't help. Oh, and don't
|
|
bother with "strings" on a .ps file: it's <EM>all</EM> text.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
[Robos]
|
|
Hmm, I ran into some ocr discussion lately and found this: gocr and claraorc
|
|
(<A HREF="http://www.claraocr.org"
|
|
>http://www.claraocr.org</A>). The latter one seems to be more evolved...
|
|
</BLOCKQUOTE>
|
|
|
|
<!-- end 5 -->
|
|
<!-- .~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~. -->
|
|
<P> <A NAME="tips.6"><HR WIDTH="75%" ALIGN="center"></A> <P>
|
|
<H3><IMG ALIGN=BOTTOM ALT="" SRC="../gx/lil2cent.gif">
|
|
<FONT COLOR="navy">quotas on directories?</FONT></H3>
|
|
Tue, 3 Jun 2003 19:55:26 +0200
|
|
<BR>Emmanuel Damons (<a href="mailto:linux-questions-only@ssc.com?cc=emmanuel.damons@enterpriseig.com&subject=%20Re%3A%20%5BLG%2092%5D%202c%20Tips%20%236">emmanuel.damons from enterpriseig.com</a>)
|
|
|
|
|
|
|
|
<br>Answered By Thomas Adma, Jim Dennis, Kapil Hari Paranjape
|
|
|
|
<P>
|
|
Hi
|
|
</P>
|
|
<P>
|
|
Can you help me I need to specify the size that a folder can grow.
|
|
almost like the quotas for folder and not users
|
|
</P>
|
|
<P>
|
|
Thanks
|
|
</P>
|
|
<BLOCKQUOTE>
|
|
[K.-H.]
|
|
spontaneous idea, especially if this is for one folder only:
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE><BLOCKQuote>
|
|
create a partiton of exactly right size and mount it at mountpoint "folder".
|
|
If creating a partition is not possible use a file and mount it a loop device.
|
|
</BLOCKQuote></BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
[JimD]
|
|
In the same concept you could use regular files with the loop mount
|
|
option to create "partitions" of this sort.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
Example:
|
|
</BLOCKQUOTE>
|
|
|
|
<blockquote><pre> dd if=/dev/zero of=/mnt/images/$FOLDERNAME bs=1024 count=$SIZE
|
|
mkfs -F /mntimages/$FOLDERNAME
|
|
mount -o loop /mntimages/$FOLDERNAME $TARGET
|
|
</pre></blockquote>
|
|
<BLOCKQUOTE>
|
|
Where:
|
|
</BLOCKQUOTE>
|
|
|
|
<blockquote><pre> FOLDERNAME is an arbitrary filename used as a "loopback image"
|
|
(the container that the loop block device driver will treat
|
|
as if it were a partition)
|
|
SIZE is the desired size in kilobytes
|
|
TARGET is the desired location of the "folder" (the mountpoint for
|
|
this filesystem).
|
|
</pre></blockquote>
|
|
<BLOCKQUOTE>
|
|
You can use any of the Linux supported filesystem types (ext2, ext3,
|
|
minix, XFS, JFS, ReiserFS) and you can tune various options (like
|
|
the amount of reserved space on such "folders" and which UID/GID
|
|
(user or group) that space is reserved for. You should be able to
|
|
use quotas, ACLs and EAs (extended attributes and access control lists)
|
|
(assuming you've patched your kernel for ACL/EA use and enabled it)
|
|
etc.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
Obviously this approach as a couple of downsides. You need
|
|
intervention by root (or some sudo or SUID helpers) to create and
|
|
use these images.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
[Kapil]
|
|
Of course, you can use User-mode-linux to create and use these images.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
[JimD]
|
|
Also Linux can only support a limited number of
|
|
concurrent loop mounts (8 by default). Newer kernels allow this as
|
|
a module parameter (max_loop=<1-255> ... so up to 255 such folders
|
|
maximum on the system). This limits the number that could be in
|
|
concurrent use (though an unlimited number of these "folders" could
|
|
be stored on the system, mounted and unmounted as needed).
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
There might be other disadvantages in performance and overhead (I'm not
|
|
sure).
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
[Kapil]
|
|
That would be a downside with UML if you use the file systems with UML.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
[JimD]
|
|
On the plus side you could have any of these encrypted, if you're
|
|
running a kernel that's had the "International crypto" patch applied to
|
|
it; and you pass the appropriate additional options to the mount
|
|
command(s). We won't address the key management issues inherent in
|
|
this approach; suffice it to say that almost forces us to make mounting
|
|
these filesystems an interactive process.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
If you wanted to have a large number of these, but didn't need them all
|
|
concurrently mounted you might be able to configure autofs or amd
|
|
(automounters) to dynamically mount them up and umount them as the
|
|
target directories were accessed --- possibly by people logging in and
|
|
out.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
There are probably better ways, but this seems to be the most obvious
|
|
and easiest under Linux using existing tools.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
[Kapil]
|
|
One solution (rather complicated I admit) is to switch over to the Hurd
|
|
which allows such things and more complicated things as well.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
Another is to use "lufs" or other "Usermode filesystems". These put
|
|
hooks in the kernel VFS that allow one to set up a "user mode" program
|
|
to provide the "view" of the part of VFS that lies below a particular
|
|
directory entry.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
[JimD]
|
|
The very notion of limiting the size of a "directory tree" (folder)
|
|
is ambiguous and moot given the design of UNIX. Files don't exist
|
|
"under" directories in UNIX. Files are bound to inodes which are
|
|
on filesystems. Filenames are links to inodes. However every inode
|
|
can have many links (names). Thus there's an inherent abiguity of
|
|
what it means to take up space "in a folder" (or "under a directory").
|
|
You could traverse the directory tree adding up all files (and the
|
|
sizes of all directories) thereunder (du -s). This works fine for all
|
|
inodes with a link count of one, and for cases where all of the inodes
|
|
are within the scope of the tree (and assuming there are no mount
|
|
points thereunder). However, it's ambiguous in the general case and
|
|
begs the question: just what are you trying to accomplish.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
[Kapil]
|
|
Excellent explanation Jim.
|
|
</BLOCKQUOTE>
|
|
|
|
<!-- end 6 -->
|
|
<!-- .~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~. -->
|
|
<P> <A NAME="tips.7"><HR WIDTH="75%" ALIGN="center"></A> <P>
|
|
<H3><IMG ALIGN=BOTTOM ALT="" SRC="../gx/lil2cent.gif">
|
|
<FONT COLOR="navy">What is Reverse DNS?</FONT></H3>
|
|
Mon, 2 Jun 2003 20:37:46 EDT
|
|
<BR> (<a href="mailto:linux-questions-only@ssc.com?cc=TEEML914@aol.com&cc=jimd@mars.starshine.org&subject=%20Re%3A%20%5BLG%2092%5D%202c%20Tips%20%237">jimd from mars.starshine.org</a>)
|
|
<BR>Question by TEEML914 (TEEML914 from aol.com)
|
|
|
|
<P><STRONG>
|
|
I'm doing an assigment. Can you tell me in laymans terms what reverse DNS is?
|
|
</STRONG></P>
|
|
<BLOCKQUOTE>
|
|
[Faber]
|
|
Yes, we can.
|
|
</BLOCKQUOTE>
|
|
<P><STRONG>
|
|
Thank you and have a great day
|
|
</STRONG></P>
|
|
<BLOCKQUOTE>
|
|
[Faber]
|
|
You're welcome and have a spiffy night yourself..
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
[JimD]
|
|
Faber, I think your cheerful sarcasm might be lost on him. After,
|
|
he's dense enought to take such a simple question (from his homework
|
|
assigment, no less) and go to all the trouble it of asking <EM>us</EM>
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
Yes, we can tell you. We can answer such questions. With dilligent
|
|
work (as in DOING YOUR OWN HOMEWORK) you'd be able to answer questions
|
|
like that, too.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
For everyone else who hears this buzz phrase and wonders about it
|
|
(people who aren't trying to skate through classes so they can make
|
|
complete idiots of themselves when they enter a job market thoroughly
|
|
unprepared by the schooling they shirked):
|
|
</BLOCKQUOTE>
|
|
|
|
<TABLE WIDTH="95%" BORDER="1" BGCOLOR="#FFFFCC"><TR><TD>
|
|
<p align="center">...............</p>
|
|
<BLOCKQUOTE><BLOCKQuote>
|
|
"reverse DNS" is the process of asking the DNS (domain name system)
|
|
for the name associated with a given IP address (which, of course, is
|
|
numeric). Since DNS is primarily used to resolve (look up) an
|
|
address given a name; this numeric to symbolic lookup is the
|
|
converse operation. However, the term "converse" is somewhat obscure
|
|
so the more literate and erudite among us are stuck with the phrase:
|
|
"reverse DNS."
|
|
</BLOCKQuote></BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
On a technical level, a reverse DNS query is a question for a PTR
|
|
record in the in-addr.arpa domain. For historical reasons the
|
|
in-addr (inverse address) subdomain of the "Advanced Research
|
|
Projects Administration" (the forebear of the Internet) is reserved
|
|
for this purpose. For technical reasons the four components of a
|
|
traditional "dotted quad decimal" representation of the address are
|
|
arranged in reverse order: least significant octet first. This
|
|
allows the most significant octets to be treated as "subdomains" of
|
|
the in-addr.arpa domain which allows delegation (a DNS mechanism for
|
|
administrative and routing/distribution purposes) to be down on
|
|
octet boundaries.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
Of course any good book on DNS will provide all of the gory details,
|
|
or one could simply read the RFCs (request for comments documents)
|
|
which are the normal mechanism by which standards are proposed to the
|
|
IETF (Internet Engineering Task Force) which marshalls them through a
|
|
review and vetting process, publishes them and recommends their
|
|
adoption. (Since the Internet is still basically anarchial the
|
|
adoption of new standards is essentially a ratification process ---
|
|
each Internet site "votes with its feet" as it were).
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE><DL><DT>
|
|
In particular it looks like you'd want to read RFC3172:
|
|
<DD><A HREF="http://www.faqs.org/rfcs/rfc3172.html"
|
|
>http://www.faqs.org/rfcs/rfc3172.html</A>
|
|
</DL></BLOCKQUOTE><p align="center">...............</p>
|
|
</TD></TR></TABLE>
|
|
<BLOCKQUOTE>
|
|
Please have your instructor send my extra credit points c/o Linux
|
|
Gazette and be sure to have him give you a failing grade in your TCP/IP
|
|
or Internet/Networking Fundamentals class.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
(In the unlikely event the assignment was to explore the use of sarcasm
|
|
by curmudgeons in the Linux community --- then bravo!)
|
|
</BLOCKQUOTE>
|
|
|
|
<!-- end 7 -->
|
|
<!-- .~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~. -->
|
|
<P> <A NAME="tips.8"><HR WIDTH="75%" ALIGN="center"></A> <P>
|
|
<H3><IMG ALIGN=BOTTOM ALT="" SRC="../gx/lil2cent.gif">
|
|
<FONT COLOR="navy">Subscribe to groups...........pan,Knode.......????</FONT></H3>
|
|
Wed, 25 Jun 2003 20:21:12 +0530
|
|
<BR>Vivek Ravindranath (<a href="mailto:linux-questions-only@ssc.com?cc=vivek_ravindranath@softhome.net&subject=%20Re%3A%20%5BLG%2092%5D%202c%20Tips%20%238">vivek_ravindranath from softhome.net</a>)
|
|
|
|
|
|
|
|
<br>Answered By Dan Wilder, Karl-Heinz Herrmann, Anita Lewis, Ben Okopnik, Jason Creighton, Heather Stern
|
|
|
|
<P><STRONG>
|
|
Hi Answer Gang,
|
|
</STRONG></P>
|
|
<P><STRONG>
|
|
Can please tell me how to subscribe to linux groups
|
|
</STRONG></P>
|
|
<BLOCKQUOTE>
|
|
[Dan]
|
|
You might start by pointing your browser (konqueror, mozilla,
|
|
lynx, w3m, netscape, and so on) at:
|
|
</BLOCKQUOTE>
|
|
|
|
<blockquote><pre>http://www.tldp.org
|
|
</pre></blockquote>
|
|
<BLOCKQUOTE>
|
|
and browse what's there. Then look at
|
|
</BLOCKQUOTE>
|
|
|
|
<blockquote><pre>http://www.linuxjournal.com
|
|
http://www.linuxgazette.com
|
|
http://www.lwn.com
|
|
http://www.linuxtoday.com
|
|
http://www.slashdot.com
|
|
</pre></blockquote>
|
|
<BLOCKQUOTE>
|
|
Then you might come back and explain in somewhat more specific
|
|
terms what you're trying to do. There are lots of Linux websites,
|
|
including documentation, news, online discussions; to get to any of
|
|
those, you just click on links.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
For e-mail discussion groups you mostly have to subscribe. How you
|
|
do that depends on what group you're interested in. Once you're
|
|
subscribed, any email you send to some submission address is duplicated
|
|
and sent to all subscribers.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
Many discussion groups have their archives open. For example, point
|
|
your browser at
|
|
</BLOCKQUOTE>
|
|
|
|
<blockquote><pre>http://www.ssc.com/mailing-lists
|
|
</pre></blockquote>
|
|
<BLOCKQUOTE>
|
|
for an overview of mailing lists hosted by SSC, publishers of Linux Journal.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
From that page you can click on list information pages and get to list
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
archives by following the links. The list information pages also let
|
|
you apply for membership in the lists. Normally you'll get a confirming
|
|
email back, and your list membership goes into effect when the list
|
|
management software receives your reply.
|
|
</BLOCKQUOTE>
|
|
<P><STRONG>
|
|
such yahoo groups ,
|
|
</STRONG></P>
|
|
<BLOCKQUOTE>
|
|
[Jason]
|
|
Well, "Yahoo groups" are just email lists, so you can subscribe to them and
|
|
read them offline. Same deal for any mailing list.
|
|
</BLOCKQUOTE>
|
|
<P><STRONG>
|
|
google groups .......
|
|
</STRONG></P>
|
|
<BLOCKQUOTE>
|
|
[Jason]
|
|
Now for newsgroups (What you call "google groups". Google groups is actually a
|
|
web interface on top of usenet.) I use leafnode (Sorry, don't have the URL,
|
|
but a google for "leafnode usenet server" would probaby turn up the homepage.)
|
|
for this. It's an easy to configure (IMHO) usenet server that only downloads
|
|
messages in groups that you read.
|
|
</BLOCKQUOTE>
|
|
<P><STRONG>
|
|
and download all messages for offline viewing using pan or
|
|
knode or any other software (Please mention the name of the software and
|
|
URL).I wan't to view the messages offline.
|
|
</STRONG></P>
|
|
<P><STRONG>
|
|
First of all I dont know whether it is possible.Can you suggest any other
|
|
methods to do so? By groups I mean any linux group, please suggest any good
|
|
linux groups if possible...and please give the address that is to be entered
|
|
in the address field of the viewer and other details.I just want to get
|
|
regular information regarding linux........thanks in advance.
|
|
</STRONG></P>
|
|
<P><STRONG>
|
|
Vivek.
|
|
</STRONG></P>
|
|
<BLOCKQUOTE>
|
|
[K.-H.]
|
|
for the offline reading: I'm not quite sure what "linux group" you are
|
|
talking about. If you want to have a look at linux websites as suggested
|
|
wwoffle is very useful for caching of webpages so you can view them at
|
|
leasure offline. Any new link you click on will be remembered and fetched
|
|
next time online. If you talk about news groups (usenet) like:
|
|
comp.os.linux.* I am using [x]emacs newsreader "gnus" which has a offline
|
|
feature called "agent". You can read the info pages to this but if this is
|
|
your first contact with news and [x]emacs then I can not recommend this
|
|
wholeheartedly -- gnus itself is rather complex and therefor powerful (or is
|
|
it the other way round?). Agent is an additional layer of complexity which
|
|
takes time to get used to.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
pan I don't know,
|
|
</BLOCKQUOTE>
|
|
|
|
<blockquote><font color="#000066">It's a newsreader, whose name might offend a family publication, but
|
|
which is nonetheless supposed to be very nifty.
|
|
-- Heather</font></blockquote>
|
|
<BLOCKQUOTE>
|
|
knode I can only guess is the kde version of a newsreader.
|
|
If they support offline features I've no idea. There are other newsreaders:
|
|
nn, tin, ... but as far as I know all miss the offline feature. netscape has
|
|
a newsreader with rather limited offline capabilities but for a first try
|
|
that might be sufficient.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
[Anita]
|
|
Do you mean that you would subscribe to a mailing list on yahoogroups and
|
|
then go there and download their archives? That is something I would like
|
|
to know how to do too, because we had a list there and changed to our own
|
|
server. I'd like to be able to get those old messages. Well, in truth, I
|
|
would have liked to have had them, but now I think they are too obsolete.
|
|
Still, I wouldn't mind having them, especially if I could get them into mbox
|
|
format.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
[Faber]
|
|
<musing out loud>Couldn't you use something like wget in a Perl script
|
|
to download the archives by links? Ben could probably write a one-liner
|
|
to do it. In his sleep.
|
|
<IMG SRC="../gx/dennis/smily.gif" ALT=":-)"
|
|
height="24" width="20" align="middle">
|
|
</musing>
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
[Ben]
|
|
Actually, it would take some tricky negotiation, Web page downloading
|
|
and parsing, etc. - it's a non-trivial task if you wanted to do it from
|
|
scratch. "Yosucker" from <A HREF="http://www.freshmeat.net/">Freshmeat</A> is a good example of how to download
|
|
their Web-only mail; it wouldn't be too hard to tweak for the above
|
|
purpose (it's written in Perl.)
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
[Jason]
|
|
You could probably just use wget, with some combination of -I and -r. The
|
|
thing is a HTTP/FTP shotgun.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
[Ben]
|
|
Nope. Remember that you need to log in to Yahoo before you can read the
|
|
stuff; after that, you get to click on the message links (20 per page or
|
|
so) to read them. If it was that easy, they wouldn't be able to charge
|
|
you for the "improved" access (which includes POP access to your mail
|
|
and a bunch of other goodies.)
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
[Jason]
|
|
Actually, I was thinking of download from an online mailing list archive, not
|
|
logging into Yahoo.
|
|
</BLOCKQUOTE>
|
|
|
|
<blockquote><font color="#000066">Perhaps a little specific encoding with lynx' ability to pick up its
|
|
transmission data from stdin ... -get_data. It's <EM>your</EM> login, so
|
|
you'll need to guard your password in that packet from prying eyes.
|
|
Like Ben says, tricky, but certainly it can be done.
|
|
-- Heather</font></blockquote>
|
|
|
|
<!-- end 8 -->
|
|
<!-- .~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~. -->
|
|
<P> <A NAME="tips.9"><HR WIDTH="75%" ALIGN="center"></A> <P>
|
|
<H3><IMG ALIGN=BOTTOM ALT="" SRC="../gx/lil2cent.gif">
|
|
<FONT COLOR="navy">Confused about symantics of "mount -o,async/sync" commands</FONT></H3>
|
|
Thu, 12 Jun 2003 21:30:21 -0700
|
|
<BR>Bombardier System Consulting (<a href="mailto:linux-questions-only@ssc.com?cc=bombardiersysco@qwest.net&subject=%20Re%3A%20%5BLG%2092%5D%202c%20Tips%20%239">bombardiersysco from qwest.net</a>)
|
|
|
|
|
|
|
|
<br>Answered By Karl-Heinz Herrmann, Thomas Adam, Ben Okopnik, Jim Dennis, Jay R. Ashworth
|
|
|
|
<P><STRONG>
|
|
Hello,
|
|
</STRONG></P>
|
|
<P><STRONG>
|
|
I am taking a local Linux certification class and seem to have offended my
|
|
instructor by questioning the semantics of the "sync" and "async" options in
|
|
the mount command. They seem backward to me and I don't understand what I
|
|
am missing.
|
|
</STRONG></P>
|
|
<P><STRONG>
|
|
The following are the definitions that I found online and understand for the
|
|
words:
|
|
</STRONG></P>
|
|
<P><STRONG><BLOCKQuote>
|
|
Synchronous (pronounced SIHN-kro-nuhs, from Greek syn-, meaning "with," and
|
|
chronos, meaning "time") is an adjective describing objects or events that
|
|
are coordinated in time. (within the context of system activities I
|
|
associate synchronous with either being timing based or requiring an
|
|
acknowledgement)
|
|
</BLOCKQuote></STRONG></P>
|
|
<P><STRONG>
|
|
Asynchronous (pronounced ay-SIHN- kro-nuhs, from Greek asyn-, meaning "not
|
|
with," and chronos, meaning "time") is an adjective describing objects or
|
|
events that are not coordinated in time. (within the context of system
|
|
activities I associate asynchronous with being event/interrupt driven).
|
|
</STRONG></P>
|
|
<P><STRONG>
|
|
It has been my experience and is my understanding with disk caching that
|
|
data that is released to the system to be written to disk is kept for a
|
|
specific time or until the cache is full before being written to disk.
|
|
Hence synchronous. It is my experience and is my understanding that data
|
|
from an application which is released to the system and is directly written
|
|
through to disk is done so in an asynchronous or event driven manner.
|
|
</STRONG></P>
|
|
<BLOCKQUOTE>
|
|
[K.-H.]
|
|
synchronous -- applications intent to write data and actual write are at the
|
|
same time
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
asynchronous -- applications intent to write and actual write are not at the
|
|
same time as system decides when to write the cached data
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
[Thomas]
|
|
These options are really useful in <TT>/etc/export</TT> if you ever need to mount
|
|
directories over NFS, too. Although just don't specify them at the same
|
|
time as each other!
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
[Ben]
|
|
Yup. The latter is more efficient, since it allows the hevy lifting to
|
|
occur all at once (one way to look at it is that the "startup" and the
|
|
"wind-down" costs of multiple disk writes are eliminated - you "pay"
|
|
only once), but is a little less secure in the sense of data safety -
|
|
if your computer is, say, accidentally powered down while there's data
|
|
in the cache, that data evaporates, even though you "know" that you
|
|
saved it.
|
|
</BLOCKQUOTE>
|
|
<P><STRONG>
|
|
This is evidently opposite of the way that the terms are understood and used
|
|
in Linux. Please help me understand.
|
|
</STRONG></P>
|
|
<P><STRONG>
|
|
Thanks,
|
|
</STRONG></P>
|
|
<P><STRONG>
|
|
Jim Bombardier
|
|
</STRONG></P>
|
|
<BLOCKQUOTE>
|
|
Put simply, ... you're wrong.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
"sync" in the Linux parlance (and in other disk buffering/caching contexts
|
|
with which I'm familiar) means that the writes to that filesystem are
|
|
"synchronized" out to the disk before the writing process is scheduled
|
|
for any more time slices. In other words, upon return from a <TT> write()</TT>
|
|
system call the write as occurred to the hardware device.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
This usage is consistent with the traditional meaning of the 'sync'
|
|
utility (part of all versions of UNIX I've used and heard of). The
|
|
'sync' utility forces the kernel to "synchronize" its buffers/caches
|
|
out to the device.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
"async" means that writes are happening asynchronously to the ongoing
|
|
events in the process. In other words mere return from the function
|
|
call doesn't indicate that the data is safely flushed to the device.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
Note that use of sync is strongly discouraged by kernel luminaries
|
|
(Linus Torvalds in particular). I sometimes choose to over-ride their
|
|
better judgement myself --- but I do so only with considerable mulling
|
|
on the tradeoffs. In general you're better off with UPS
|
|
(uninterruptable power supply) and a journaling filesystem than you'll
|
|
ever be by trying to force synchronous writes for an entire filesystem.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
Of course, with open source packages you can opt for aggressive explicit
|
|
synchonization of selected file descriptors using the <TT> fsync()</TT> function.
|
|
Note that this can lead to poor overall system performance in some
|
|
cases. For example MTAs (mail transport agents) and syslogd both make
|
|
extensive use of <TT> fsync()</TT>. If they share the same filesystem (<TT>/var/log</TT>
|
|
and <TT>/var/spool</TT> are on a single volume) it can make the entire system
|
|
feel sluggish under only moderate mail handling load (as each mail
|
|
delivery logs several messages and each of those processes runs
|
|
its on <TT> fsync()</TT> calls.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
[jra]
|
|
You know, the way I've always interpreted this is that it describes the
|
|
coupling between the application program's logical view of the disk
|
|
contents and the actual physical, magnetic contents of the drive,
|
|
across time:
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE><BLOCKQuote>
|
|
those views are either mandated to stay in "sync" -- no buffering; if
|
|
the OS says it's written, it is <EM>on the platters</EM>, or they're "async"
|
|
-- the OS is permitted to "cheat" a little bit in between when it tells
|
|
the <EM>app</EM> "it's written" and when it actually happens.
|
|
</BLOCKQuote></BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
I guess it's really just another way of phrasing the same thing...
|
|
</BLOCKQUOTE>
|
|
|
|
<!-- end 9 -->
|
|
<!-- .~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~.~~. -->
|
|
<P> <A NAME="tips.10"><HR WIDTH="75%" ALIGN="center"></A> <P>
|
|
<H3><IMG ALIGN=BOTTOM ALT="" SRC="../gx/lil2cent.gif">
|
|
<FONT COLOR="navy">Linux Journal Weekly News Notes - Tech Tips</FONT></H3>
|
|
Mon, 23 Jun 2003 01:29:49 -0700
|
|
<BR>Linux Journal News Notes (<a href="mailto:linux-questions-only@ssc.com?cc=lj-announce@ssc.com&subject=%20Re%3A%20%5BLG%2092%5D%202c%20Tips%20%2310">lj-announce from ssc.com</a>)
|
|
|
|
|
|
|
|
<h4 align="center"><br>Cut Them Off At The Pass
|
|
</h4>
|
|
<P>
|
|
If someone's script is going haywire and making too many connections
|
|
to your system, simply do:
|
|
</P>
|
|
<P><CODE>
|
|
route add -host [hostname]
|
|
</CODE></P>
|
|
<P>
|
|
...to keep the offending box from shutting yours down entirely.
|
|
</P>
|
|
<HR width="10%" align="center">
|
|
<h4 align="center"><br>Log A Lot Less
|
|
</h4>
|
|
<P>
|
|
You can turn off syslogd's MARK lines by invoking them with -m 0. You
|
|
can put this invocation in the init script that starts syslogd. This
|
|
is especially useful on laptops to keep them from spinning up the hard
|
|
drive unnecessarily.
|
|
</P>
|
|
<HR width="10%" align="center">
|
|
<h4 align="center"><br>Watch a Bit More
|
|
</h4>
|
|
<P>
|
|
Using the watch command, you automatically can run the same command
|
|
over and over and see what changes. With the -d option, watch
|
|
highlights the differences. Try it with watch -d ifconfig.
|
|
</P>
|
|
<HR width="10%" align="center">
|
|
<h4 align="center"><br>Rooting Around with LILO
|
|
</h4>
|
|
<P>
|
|
If you are working from a rescue disk with your normal root partition
|
|
mounted as <TT>/mnt/root</TT>, you can reinstall the LILO boot sector from your
|
|
<TT>/etc/lilo.conf</TT> file with lilo -r <TT>/mnt/root.</TT> This tells LILO(
|
|
<IMG SRC="../gx/dennis/smily.gif" ALT="8)"
|
|
height="24" width="20" align="middle"> to
|
|
chroot to the specified directory before taking action. This command
|
|
is handy for when you install a new kernel, forget to run LILO and
|
|
have to boot from a rescue disk.
|
|
</P>
|
|
<HR width="10%" align="center">
|
|
<h4 align="center"><br>Removing Files Starting With Dashes
|
|
</h4>
|
|
<P>
|
|
If you want to remove a file called -rf, simply type rm -- -rf. The --
|
|
tells rm that everything after -- is a filename, not an option.
|
|
</P>
|
|
|
|
<blockquote><font color="#000066">The LG staff note that ./ (dot slash) preceding the offending filename
|
|
is effective too, and works even on older versions of rm - or non linux
|
|
systems - that may not have this handy option.
|
|
-- Heather</font></blockquote>
|
|
<HR width="10%" align="center">
|
|
<h4 align="center"><br>Any Program Can Learn To Read
|
|
</h4>
|
|
<P>
|
|
If you have a program that reads only from a file and not from
|
|
standard input, no problem. The <TT>/proc</TT> filesystem contains a fake file
|
|
to pass such programs their standard input. Use <TT>/proc/self/fd/0.</TT>
|
|
</P>
|
|
|
|
<!-- end 10 -->
|
|
<!-- *** BEGIN copyright *** -->
|
|
<hr>
|
|
<CENTER><SMALL><STRONG>
|
|
<h5>This page edited and maintained by the Editors of <I>Linux Gazette</I><br>HTML script maintained by <A HREF="mailto:star@starshine.org">Heather Stern</a> of Starshine Technical Services, <A HREF="http://www.starshine.org/">http://www.starshine.org/</A>
|
|
<br>Copyright © 2003
|
|
<br>Copying license <A HREF="http://www.linuxgazette.com/copying.html">http://www.linuxgazette.com/copying.html</A>
|
|
<BR>Published in Issue 92 of <i>Linux Gazette</i>, July 2003</H5>
|
|
</STRONG></SMALL></CENTER>
|
|
<!-- *** END copyright *** -->
|
|
<HR>
|
|
|
|
|
|
<!--startcut ==========================================================-->
|
|
<CENTER>
|
|
<!-- *** BEGIN navbar *** -->
|
|
<A HREF="lg_mail.html"><< Prev</A> | <A HREF="index.html">TOC</A> | <A HREF="../index.html">Front Page</A> | <A HREF="http://www.linuxgazette.com/cgi-bin/talkback/all.py?site=LG&article=http://www.linuxgazette.com/issue92/lg_tips.html">Talkback</A> | <A HREF="../faq/index.html">FAQ</A> | <A HREF="lg_answer.html">Next >></A>
|
|
<!-- *** END navbar *** -->
|
|
</CENTER>
|
|
</BODY></HTML>
|
|
<!--endcut ============================================================-->
|