How to restore permissions in /usr/lib folder?

Solution 1:

I followed these steps, from How to Easily Back Up and Restore Linux File Permissions, to get a backup of permissions using another ubuntu system (by booting from a Ubuntu USB image) and then restored it. It works.

To backup permissions:

getfacl -R TEST > test_permissions.txt

To restore permissions:

setfacl --restore=test_permissions.txt

Solution 2:

This is not recommended, but probably what I would have done:

$ dpkg -S '/usr/lib/*' | \
  cut -d : -f1 | sed 's/, /\n/g' | sort -u >> dpkg-package.log

This creates a package list of all packages that have files in /usr/lib, the next step is to sort out locally installed or non-installable packages.

$ xargs -a ./dpkg-package.log apt-get --dry-run reinstall

If apt-get complains about packages, move them from the dpkg-package.log to dpkg-temp.log. When you are ready to reinstall, just remove the --dry-run option. This will restore the permission on the reinstalled files.