Created Thu Sep, 03 2020 at 08:50PM

Original thread:

  1. Find out what package installed the config file:

$ dpkg -S unity-greeter.conf unity-greeter: /etc/lightdm/unity-greeter.conf

As you can see, the name of the package is unity-greeter.

If you deleted a directory, like /etc/pam.d, you can list every package that added to it by using the directory path:

$ dpkg -S /etc/pam.d login, sudo, libpam-runtime, cups-daemon, openssh-server, cron, policykit-1, at, samba-common, ppp, accountsservice, dovecot-core, passwd: /etc/pam.d

  1. Run the following command, replacing <package-name> with the name of the package:

sudo apt install --reinstall -o Dpkg::Options::="--force-confask,confnew,confmiss" <package-name>

And for restoring the directory:

sudo apt install --reinstall -o Dpkg::Options::="--force-confask,confnew,confmiss" $(dpkg -S /etc/some/directory | sed 's/,//g; s/:.*//')

  1. If everything worked as expected, you should get a message:

Configuration file `/etc/lightdm/unity-greeter.conf', does not exist on system. Installing new config file as you requested.

  1. A Practical example when needing to reinstall all of the PulseAudio configuration files:

apt-cache pkgnames pulse |xargs -n 1 apt-get -o Dpkg::Options::="--force-confmiss" install --reinstall