pam bugs hurt

I did some upgrades of what seemed like a million packages today on my Debian sid computer.  I was doing this remotely and when I tried to ssh back in I got kicked out after entering my password, hmmm.

OK, so I waited until I could get in front of it and tried to login to the console and was greeted with the message “Cannot make/remove an entry” and kicked out, even as root; double hmmm.

So it was boot into single user time which, thankfully worked. bash loaded ok so it wasn’t a shell problem.  However su failed which means we are into pam problem territory.  I found a bug report that sounded like my problem, but with no clear solution except upgrade in Ubuntu.


The solution was pretty simple for me.  It’s something funky with /etc/pam.d/common-sesssion and a simple ‘/usr/sbin/pam-auth-update’ fixed it for me.



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MediaServer with Rygel

Rygel XVI
Image by Cayusa via Flickr

Like a lot of  people, I have one of those set-top TV boxes that can record TV shows at set times.  I made sure that I could get at the files (using a FTP server in this case) and that the files were some sort of common standard (MPEG 4 TS).  I also have a bunch of mp3 music files.

That’s fine when I’m on the desktop because the files are local.  I wanted to make these available to anyone in the household. DLNA seemed to be a reasonably OK way of doing this, the problem was, how to get it working in Linux?

A lot of the problem is that it is hard to find a DLNA only server.  Sure MythTV could do it, but it needs a tv tuner or a lot of fiddling around.  XMBC can also do it, but it needs to be running a GUI.  I even tried mediatomb but could not get the thing to compile as the library calls to mozjs were all using deprecated functions. I just wanted a daemon that served stuff, nothing more; no fancy ui, no need for X just file serving goodness.

Rygel is almost that.  You could say it is a user server much like a torrent client/server.  The nice thing is you can fiddle around with rygel so it becomes close to a real server.  This is how I did it.

First, I made a rygel user with a home directory, but disabled login. I don’t like programs running root if they don’t need it and rygel doesn’t need it.  The home directory needs to be writeable to the rygel user too otherwise the program doesn’t work too well. I use /var/local/rygel as its home.

For the configuration, copy /etc/rygel.conf to ~rygel/.config/rygel.conf  This is the configuration file for rygel. I disabled all of the modules except MediaExport. Make sure you disable Tracker otherwise MediaExport will not work. Tracker is only useful for real users who are logged in and have dbus etc going which this user is certainly not.

I made a simple rygeld file in /usr/local/sbin which basically starts the program, forks and grabs the PID to write to a pidfile. This mean it was easier to track the program in the init scripts.

# Rygel daemon handling
su -s /bin/sh -c "nohup $RYGEL $RYGEL_ARGS > /var/local/rygel/rygel.log 2>&1 &"
if [ $EXIT_CODE != 0 ] ; then
        return $EXIT_CODE
PGROUP=`ps --no-headers -o pgrp $$`
PID=`pgrep -g $PGROUP -f $RYGEL`
echo $PID > /var/run/
exit 0

In case you were wondering, the pgrp finds the program group so the pgrep finds the right rygel process that has the same program group as the starting shell.

The init script is a standard init script except the –exec flag checks for /usr/bin/rygel but the start line starts /usr/local/sbin/rygeld  This is because we want to kill the real rygel process but start it with the script.

This setup works rather well. You do get some messages in the logfile about dbus not working but it is harmless. I tried disabling the mpris and external plugins but no matter what flag or configuration file option I tried, they would always try to start and fail with no dbus.

Rygel is a a reasonably light-weight way of serving media to your home network. It idles 200 MB virtual with 16MB resident and when idle uses almost no CPU.


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Debian Linux on HP DV6-6023TX

It was time to update my creaking old laptop.  I ordered HP6-6023TX online and after a few days it arrived just before a long weekend.

I first backed up Windows 7 onto a set of DVDs and found that either my blank DVDs are old or this new DVD drive is far more fussy. There were quite a few coasters made until I gave up and bought some new ones.

DVDs seemed to be trouble for me that day.  I downloaded the Debian 6.0.4 DVD image but couldn’t burn it. Brasero would just keep saying calculating checksum and go no further.  So after waiting too long, the CD iso was downloaded and installed.

Installation of Debian onto the laptop was straightforward. That is if you used a wired connection. Wireless needs the non-free firmware and I gave up trying to work out how to install it at debian-installer time as it didn’t see the tar.gz full of firmware on the USB stick.  Wireless worked perfectly once I loaded everything on. So at this point with not much trouble I had an almost fully working setup. Even the webcam and sound was working.

Video Fun

The laptop is one of these strange modern ones that has two video cards.  The low-spec one is an Intel Sandybridge while the higher one is an AMD/ATI Radeon HD 6700M. The idea being you use the ATI when plugged in and the Intel on batteries.

Xorg worked first go, but only on the Intel chip.  Trying to force X to use the ATI driver with an Xorg configuration resulted in the Xserver crashing.

Next attempt was the fglrx packages within Debian. aticonfig said it didn’t know about the card. The reason for this is that the Debian packages use fglrx version11.4 and I needed for my card 11.5 So close but so far away.

OK, so building the ATI software can’t be that hard can it?  A nice set of instructions on the Debian wiki and we had… errors. The first problem is that the packaging used is ancient. The second problem is much more serious; it won’t compile.

I was stuck about here until I hopped onto the Debian irc channel and asked about it and someone found a very useful webpage about compiling the ATI drivers on Debian which importantly had information about the patches you need, especially the blk patch.

Success! the program compiled and installed. A small xorg.conf specifying the fglrx driver and the BusID and we were up and running.  I now have accelerated graphics on the laptop.

Ouch, my eyes!

I do actually get outside (one of my hobbies is gardening and that is an outdoor activity) so I don’t need a monitor screen trying to give me a suntan.  The default screen brightness on the laptop could be described as “sub-nova”. I’m sure there is some alien astronomers several light-years away who will in many years time wonder what that flash from the unimpressive end of the milky-way was about. To protect your eyes and keep the neighborhood complaints down you can reduce the brightness to something sane. You do this in the power management settings which for me is System -> Preferences ->  Power Management. I can see again!

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