apt
Debian and Ubuntu package manager.
Official documentation- apt: Could not get lock /var/lib/dpkg/lock-frontendapt fails with Could not get lock /var/lib/dpkg/lock-frontend while another apt, dpkg or unattended-upgrades runs. Wait for it; never delete the lock.
- apt: E: Unable to locate packageapt install fails with E: Unable to locate package when package lists are outdated, the name is wrong, or the package is in a repository that is not enabled.