I can confirm it's in a default installation, see the
/usr/share/base-passwd/passwd.master file provided by the
According to the documentation from that package, it is used for backup accounts without requiring full root permissions (which is available at
/usr/share/doc/base-passwd/users-and-groups.html and online):
Presumably so backup/restore responsibilities can be locally delegated to
someone without full root permissions?
HELP: Is that right? Amanda reportedly uses this, details?
Note the keyword locally, for remote backups you have to enable a login shell first. You are free to use it for your own purposes, but note the above guide lines. Do not grant
sudo policies for example that would allow the backup user to escalate its privileges to root.