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Andrew Pollock


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Thursday, 30 June 2005

More fun and games: running Sarge in a UML

Once I'd got the underlying UML host system installed, I set about creating a couple of UML instances, one for the 2006 linux.conf.au guys, and one for mucking around in, and will be for the 2007 guys when they want to get the ball rolling.

Next I ran into some bizarre problems with UML. The host is running a 2.6.8 kernel with the SKAS patch, and the UMLs themselves are running 2.6.10. I used rootstrap to create the initial filesystem, and then jumped on the console to install OpenSSH, and then SSH in to do the rest of the configuration.

The problem was I got struck by #298427, which is indeed a bizarre little bug. I initially worked around this by reconfiguring the SSH daemon not to use PAM and setting PasswordAuthentication to yes. I later hit some strange segmentation faults with BIND 9 as well, so I tried the alternative workaround I had subsequently found, which was to move /lib/tls out of the way.

Given that this seems to fix the problem, and it's bigger than just SSH, I'm guessing the problem is actually some sort of libc6 + UML + 2.6.10 problem or something, although I haven't had this problem previously, and I was using the exact same UML kernel and host kernel, so it's a bit odd. Maybe its a Celeron thing or something. I don't know what the implications are of having /lib/tls nonexistent at the moment either, but it can't be ideal.

[03:08] [tech] [permalink]

Fun and games: installing Debian into a chroot

I was added to the Linux Australia sysadmin team shortly after linux.conf.au. To date, I've just been picking around the edges of stuff that needs doing on digital, but this week I got to really sink my teeth into stuff.

The 2006 linux.conf.au guys didn't have a server to host the website on, so LA acquired one specifically for this purpose. What we decided to do was use User Mode Linux to provide a virtual server for the 2006 guys, with a second one on standby for the 2007 guys.

The physical server is living with Jon Oxer in Adelaide at Internet Vision Technologies. I had the job of installing Linux on it.

Jon had done a quick install of Ubuntu on the first disk (it has two SATA disks) and so what I decided to do (as I wanted to use Sarge) was install Debian onto the second disk. I also wanted to mirror the disks, so I created a degraded RAID-1 array out of the second disk, created an LVM physical volume out of one of the arrays (with the associated volume group and logical volumes), and proceeded to try and install Sarge in a chroot onto this.

This went fairly well, except I ran into a few issues with the initrd. Because when Jon swapped it around to boot from the second disk, what was /dev/sdb became /dev/sda, and everything that had hardcoded devices in it promptly freaked out on bootup. I ended up dealing with this by making the initrd myself with the -k option, and tweaking the script that assembled the RAID array, as well as making sure the right devices existed. Poor old Jon had to switch back to the temporary install on the first disk a few times for me until I successfully got everything to work, but I really enjoyed working through the issues and further improving my understanding of Debian's initrd. It really does make the bootup a bit... fragile.

Once I managed to successfully boot from the degraded RAID array on /dev/sda (previously /dev/sdb), I copied the partition table across, and hot-added the second disk to the array and let it rebuild.

[03:02] [tech] [permalink]