• Globally adding X startup commands on Debian
• .Xauthority files for Debian startx
• for remote X client access: USE SSH with X11 forwarding!
• 2C Tip Root Password
• 2C Answers: RH7.1 switch to KDE login as default
• 2 cent tip: a quick email address finder
• djbdns? Feh! Get a free-software name server instead
• Your article about rbl going commercial?
• Printer setup on Slackware 8?????
• Seg Fault
• SMTP Auth with Debian potato and exim
• Source control
• Kernels?? on a Sparc
• portal for a newbie?

Globally Adding X Startup Commands on a Debian System

Sometimes you'd like to configure an application so that it starts for any user who uses 'startx' (or logs in through xdm?). For example, I have a policy on my systems that all users should be running xautolock (a program that invoke an xscreensaver or xlock module after a period of mouse/keyboard inactivity).

On a Debian Woody/Sid (2.2 or later) system this can be done by copying or linking a file into /etc/X11/Xsession.d/. This would be a script similar to one you'd add to /etc/init.d/. For example I added a file called 60xautolock consisting of the single line:

/usr/bin/X11/xautolock -time 2 -corners 00-+ -cornerdelay 2 &

I suspect it should be marked as executable; I just set the perms on mine to match the others therein.

(BTW: this xautolock enables a "blank now" hot spot in the lower right corner of the screen, and a "never blank" hot spot in the lower right; so a user can blank the screen with a 2 second delay by shoving their mouse pointer far into the corner; it also sets the automatic blanking to occur in 2 minutes: the default of 10 min. is way too long!)

.Xauthority files for Debian startx

Here's another Debian tip:

Debian normally configures xdm to invoke the X server with the -auth argument. This allows one to configure their X session to allow remote clients, or local clients under other user IDs to connect to the X server (to run in your X session).

This is useful even if you've accepted the recommendation to configure Xfree86 4.x with the "-nolisten tcp" option (to disable remote clients from direct X protocol access). It allows you to run X under you're own user ID while allowing root to open programs on your display (particularly handy if you want to run ethereal, which will refuse to run SUID/root but which needs access to X and root permission to sniff on your network interfaces).

The problem is that Debian doesn't normally invoke X with the -auth option when you use the startx script. Of course you could use xhost +localhost; but this allows any local user to access your X session; rather than allowing you to control it in a more fine-grained fashion.

The solution is to edit the /etc/X11/xinit/xserverrc file, inserting one command and adding an option to another:

#!/bin/sh
/usr/bin/X11/xauth add :0 . $(dd if=/dev/urandom count=2 2> /dev/null | md5sum)
exec /usr/bin/X11/X -dpi 100 -nolisten tcp -auth $HOME/.Xauthority
## . . . . . . . . . . . . . . . . . . . . ^^^^^^^^^^^^^^^^^^^^^^^

... last comment line (starting with ##) underscores the addition to that command. The xauth command is being used to create the ~/.Xauthority file.

For root to gain access to this session you'd issue a command like:

xauth -f ~$YOU/.Xauthority extract - `hostname`/unix:0 | xauth merge -

... from a root shell (perhaps by opening an xterm and using the su or sudo commands). (Hint: obviously anyone who can read your .Xauthority file can use it to gain access to your X sessions; so maintaining these on NFS home directories is BAD; yet another reason why NFS stands for "no freakin' security").

for remote X client access: USE SSH with X11 forwarding!

That's the easiest and most secure means available for supporting remote X clients; if you call the OpenSSH client with the -X (enable/request X11 forwarding) and if the remote ssh daemon allows it; and if you have your DISPLAY variable set (which is always the case when you start an xterm under X; since it's how the X libraries linked into xterm "found" your X server) then the remote daemon will spawn off a proxy --- an instance of the daemon that will "pretend" to be an X server on display number 10, 11, or higher. That daemon will automatically relay Xprotocol events to your client which will relay them through the local Unix domain socket to your server. This is all automatic with most versions of ssh (except for the newer OpenSSH client which defaults to disabling X11 forwarding and thus requires the -X switch).

Please make sure you use capital X, as -x in lowercase tells it to disable this feature, even if the local sysadmin has chosen to okay a tunneled X connection by default. -- Heather

This allows you to run X with ports 6000 (and up) closed; (preventing remote systems from even seeing that you're running it; much less giving them the opportunity to attack your X server) and still allows you to easily support remote X clients.

SSH X11 forwarding also works through NAT/IP masquerading and any firewall that allows other ssh traffic.

2C Tip Root Password

This matter has come up many times before, and will surely come up many times in the future. I hope by putting Yan-Fa's crisp description and our extra notes in Tips, that more people who need it, will find it easily. -- Heather

Things to look out for, however:

• That actually depends on how your system is configured. For instance, the default Debian configuration makes you type in the root password before going into single-user mode. -- Mike
  That feature is called sulogin. -- Heather
• Another way to do this: at the bootprompt, enter
  kernelImageName init=/bin/sh
  No password required, unless you've been so prudent as to include
  password=something
  restricted
  in your lilo.conf before running lilo.
  -- Dan Wilder

2C Answers: RH7.1 switch to KDE login as default

If you like to get your hands dirty you can also edit the /etc/sysconfig/desktop file (or create it if it doesn't exist) and put in the line: DESKTOP=KDE

This has the added advantage of changed the XDM to KDM instead of GDM.

Y

2 cent tip: a quick email address finder

Hi,

From the Department of Scripting Newbieville, here's a tiny function I've added to my .bashrc and ended up using quite often:

addy ()
{
  if [ $# -eq 1 ]
  then
    grep -i "$1" "$HOME/.mail_aliases" | mawk '{ print($3) }'
  else
    echo "Usage: addy <searchstring>"
  fi
}

Given a search string (part of a name, nickname or address) as input, it'll output any matching email addresses it finds in an email aliases file (~/.mail_aliases, in this case). The alias file contains lines in the format used by mutt - for example:

alias nickname whoever@wherever (Real Name)

If you use WindowMaker and have xmessage, you can add something similar to a menu by adding the following, as a single line, to the menu config file of your choice:

"Find email address..." SHEXEC "xmessage -nearmouse
  `grep -i \'%a(Email address finder,Enter search string:)\'
  .mail_aliases | mawk '{ print($3) }'`"

Thanks to everyone involved with Linux Gazette - you're great!
Tim

djbdns? Feh! Get a free-software name server instead

Hmm, Answer Gang recommended djbdns without mentioning that it's proprietary software? Ouch. Bad gang, no biscuit.

Thanks Rick! Everyone else, I hope you find this particular 2c tip especially handy. I'd enjoy hearing some folks will tell us how useful or annoying they find these things.

Your article about rbl going commercial?

I see no signs that they want any money from me. Can you point me to a URL that wants payment?

Sure.

Here's the subscription policy page, clarifying that their stuff is subscription-only now, and why:

http://www.mail-abuse.org/subscription.html

Here's the Fee Structure page that it points to:

http://www.mail-abuse.org/feestructure.html

(note, you really want tables support to read that)

... so it merely depends on who you are.

Printer setup on Slackware 8?????

The Answer Gang replied with a few distro specific notes:

• On RH it is still printtool (symlinks to printconf-gui)
  -- Mike at cyborg-group
• Slackware: apsfilter is what you will probably want to use. You can find it in /usr/lib/apsfilter. There is a setup program that you can run. It's not as friendly as printtool, but it should get you going.
  -- Daniel S. Washko
• Slackware: Look in /usr/doc/apsfilter-6.1.1. The setup program should be
  /usr/lib/apsfilter/SETUP
  but I have no idea what replaced printtool. I always used apsfilter.
  -- Andrew Higgs

Seg Fault

Not really sure how to get this where it needs to go.

This is the right place. It will be published in next month's 2-Cent Tips, unless Heather has too much other material. -- Mike

I have recently had the same problem with random seg faults that you addressed in August TAG.

I bought a new computer, pieced it together, and put 384M in it. When I initially installed linux, it was dog slow, and running top, I noticed that I only had 64M visible (I think, incredibly less that 384 to be sure). I did a little checking and learned that the motherboard has a known problem of not seeing all the memory. So I entered the line "mem=384M". I then started getting random seg faults. I couldn't figure it out for a long time.

Even though I had a graphics card with on-board memory, my bios still alotted 64M to the AGP device on the motherboard. I reduced this (couldn't get rid of it, or set to 0), and allowed for the use in my lilo.conf entry, and all is wonderful now.

Sorry about the verbosity.

-Tom

SMTP Auth with Debian potato and exim

Hi,

I have done some reading and searching but the solution to our problem still eludes me.

I volunteer for a non-profit freenet ccil.org and would like to setup smtp authenication so that CCIL users who buy connectivity from other ISP's will continue to use our stable and reliable mail sevices. The system our mail runs on is a Debian potato box running the default smtp server exim.
Can you point me to a HOWTO?

Thanks,
Chuck

Are you asking how to allow users of your systems to access mail on your system even though they are not in your domain? If so, you want a program called pop-before-smtp (here's one URL I found over on google: http://rpmfind.net/linux/RPM/PLDtest/i686/pop-before-smtp-1.21-3.noarch.html ).

It's easy to setup and allows your users to access their email from anywhere in the world.

-- Sincerely, Faber Fedor

Source control

Has anybody tried Subversion? According to the web page (http://subversion.tigris.org), it's at Milestone 2 alpha development, and aims to have all CVS features plus:

• versioning of directories, permissions, etc.
• symbolic and hard links.
• better merge algorithm to minimize conflicts requiring human intervention.
• natively client/server.

It was recommended by someone on the Cheetah (http://www.cheetahtemplate.org) mailing list.

At print time, it reached its Milestone 3, is now self hosted (they use their own code and not CVS anymore), and they hope to be feature complete in early October.

Compare also Bitkeeper, (www.bitmover.com), a project by Larry McVoy and others aimed toward successful source control of big, complicated projects. -- Heather

Kernels?? on a Sparc

It should automatically detect the architecture it's compiling on and produce the right kernel.

However, whenever you install a new kernel, you always want to have a plan of escape in case the new kernel doesn't boot. That means making sure your old kernel is still ready to go and you know how to switch back to it. Popular ways to do this are to put the new kernel on a boot floppy, leaving the hard-disk setup alone, or arranging for LILO to boot one or the other from its menu. I'm not sure if Sun computers have LILO (Alphas use a multi-OS program called MILO instead), but they should have something equivalent. -- Mike

portal for a newbie?

The Gang replies:

• Metadot (http://freshmeat.net/projects/metadotportalserver)
  is a nice portal software.... I use it at http://www.gmnow.net
  -- Guy
• Mike Orr mentions several ...
  The best ones are based on a widely-used programming language and allow customization in that language, in case the default features are not adequate. You could also write your own in Python, PHP or as a Java servlet.
  • Python-based:
    • Zope (http://www.zope.org).
      You can use the default portal user interface or design your own using Zope's tools.
    • There are also Zope Products like Squishdot you can plug in that offer an alternate user interface, talkback features, etc.
    • Webware (http://webware.sourceforge.net) is not a portal but provides modular tools to build one.
  • PHP-based: PHP Nuke (http://phpnuke.org). Warning: low on documentation.

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Published in issue 70 of Linux Gazette September 2001

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