I get this error when trying to apt-get install openssh-server on my (up to date) Buster system:
Error: GDBus.Error:org.freedesktop.systemd1.UnitMasked: Unit -.mount is masked. I tried (based on the reference below): root@s32:/# systemctl unmask org.freedesktop.systemd1.UnitMasked Unit org.freedesktop.systemd1.UnitMasked.service does not exist, proceeding anyway. I don't really have a clue. One googled page suggests <quote> Situation Checking the status of a service shows it is masked. Running systemctl unmask <unit file> doesn't change the status. Resolution The systemd unit file is empty. Replace it in /usr/lib/systemd/system by reinstalling the package in which the unit file was contained. </quote>
