Fixing a broken update

So I screwed up an update (due to having a full system disk - oops!) and all of a sudden my mac will only boot to a flashing bue screen of doom. Not good. So I did some searching around and found out that:
1. Mac updates aren't rollback-able
2. You can run software update as a CLI tool
3. You can mount and install things from DMG's via CLI tools

Skipping over point 1, here's how I restored my system:

First, I was a bit lucky. I could log in from a remote terminal. I ssh'ed in and looked in /var/log/system.log to see what the hell was going on - seemed that the login window was somehow crashing - nice:

Nov 19 14:15:01 Hilbert crashdump[5914]: loginwindow crashed
Nov 19 14:15:01 Hilbert /System/Library/CoreServices/loginwindow.app/Contents/MacOS/loginwindow: Login Window Application Started
Nov 19 14:15:02 Hilbert crashdump[5914]: crash report written to: /Library/Logs/CrashReporter/loginwindow.crash.log

I was fairly sure that the problem was due to the failed update, so looked for a rollback tool (404 really useful tool not found). I then looked for a way to reinstall that update.

Following this life hack I tried to reinstall the update. Sadly this isn't possible using the softwareupdate tool, but I include it here for completeness - it might be a useful thing to know one day...

Next up I downloaded the DMG of the update from the apple site (wget is so good), mounted it:

hdiutil attach MacOSXUpd10.4.11Intel.dmg

Checked I had the room:

df -h
Filesystem                Size   Used  Avail Capacity  Mounted on
/dev/disk0s2               74G    73G   1.1G    99%    /
devfs                     100K   100K     0B   100%    /dev
fdesc                     1.0K   1.0K     0B   100%    /dev
                   512K   512K     0B   100%    /.vol
automount -nsl [201]        0B     0B     0B   100%    /Network
automount -fstab [212]      0B     0B     0B   100%    /automount/Servers
automount -static [212]     0B     0B     0B   100%    /automount/static
/dev/disk1s3              205M   144M    61M    70%    /Volumes/Mac OS X 10.4.11 Update (Intel)

And then set it installing:

sudo installer -pkg MacOSXUpd10.4.11Intel.pkg -target "/"

It seemed to take a while (it took some time with the GUI interface, too, though there I could see a progress bar), but it seemed to do the trick, the update completed and the login ran fine. I rebooted the machine, to finish the update, and after a wait that was a bit to long, everything was back to normal - phew!

Lessons learnt:
1. Never turn off sshd
2. Install Leopard, run regular backups
3. Never install a software update with a full system disk