postinst is in libvulkan1 1.0.8.0+dfsg1-0ubuntu1.
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 | #!/bin/sh
set -e
case "$1" in
configure)
ldconfig
esac
exit 0
|