preinst is in libc6-i386 2.15-0ubuntu10.
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
(upgrade|install)
if dpkg --compare-versions "$2" lt "2.13-23ubuntu1"; then
if [ -f /etc/ld.so.conf.d/biarch-compat.conf ]; then
mv /etc/ld.so.conf.d/biarch-compat.conf \
/etc/ld.so.conf.d/zz_${DPKG_MAINTSCRIPT_PACKAGE#*-}-biarch-compat.conf
fi
fi
;;
esac
|