postrm is in xserver-xorg-core 2:1.15.1-0ubuntu2.11.
This file is a maintainer script. It is executed when installing (*inst) or removing (*rm) the package.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 | #!/bin/sh
set -e
case "$1" in
purge)
rm /var/log/Xorg.*.log || true
rm /var/log/Xorg.*.log.old || true
;;
esac
# vim:set ai et sts=2 sw=2 tw=0:
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