postrm is in friendly-recovery 0.2.25.
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 15 | #!/bin/sh
set -e
case "$1" in
    remove)
        # Update grub
        if [ -e /boot/grub/grub.cfg ] && [ -x "$(which update-grub)" ]; then
            update-grub
        fi
    ;;
esac
exit 0
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