prerm is in plymouth-theme-kubuntu-text 1:14.04ubuntu15.
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 16 17 18 19 20  | #!/bin/sh -e
error()
{
    RET=$?
    MSG=$1
    echo "E: $MSG";
    exit $RET
}
if [ "x$1" = xremove ]; then
    update-alternatives \
        --remove text.plymouth /lib/plymouth/themes/kubuntu-text/kubuntu-text.plymouth  || error "Failed to update-alternatives"
    rm -f /lib/plymouth/themes/kubuntu-text/kubuntu-text.plymouth
fi
exit 0
 |