What is the scope of /var/log/user.log file?
/var/log/user.log
What’s the scope of this log file?
Is it related only to currently logged in user or to multiple users and which ones?
What this log file is about and when should I look into it?
The syslog module provides system logging utilities in Linux. Log messages have a facility (the "creator" of the message) and a level (the "severity" or "priority" of the event).
From the logger manpage:
Valid facility names are: auth, authpriv (for security information of a sensitive nature), cron, daemon, ftp, kern, lpr, mail, news, security (deprecated synonym for auth), syslog, user, uucp, and local0 to local7, inclusive.
Valid level names are): alert, crit, debug, emerg, err, error (deprecated synonym for err), info, notice, panic (deprecated synonym for emerg), warning, warn (deprecated synonym for warning). For the priority order and intended purposes of these levels, see syslog(3).
So /var/log/user.log contains log messages generated by all user-level processes running on the system: user logins, activities performed by user-level applications, etc. It is hence related to all users.
Which user-level events get logged depends on the specified logging level and the level of the event.