postrm is in linux-image-extra-3.2.0-126-virtual 3.2.0-126.169.
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 | #!/bin/sh
case "$1" in
remove|purge)
depmod -a -F /boot/System.map-3.2.0-126-virtual 3.2.0-126-virtual
update-initramfs -u -k 3.2.0-126-virtual
;;
esac
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