This command uses the file /etc/default/lock. This file has two
DEFLOGOUT = number
MAXLOGOUT = number
DEFLOGOUT specifies the time in minutes that a terminal will remain locked before the user is logged out. The default value is set to 30 minutes; this is overridden if the -number option is used on the command line. If DEFLOGOUT and -number are not specified, the MAXLOGOUT value is used.
MAXLOGOUT is the maximum number of minutes a user is permitted to lock a terminal. The default value is 60 minutes. If a user attempts to lock a terminal for longer than this time, lock will issue a warning to the user that it is using the system maximum time limit. If DEFLOGOUT and -number and MAXLOGOUT are not specified, users are not logged out.
DEFLOGOUT and MAXLOGOUT are configured by the system administrator to reflect the demand for terminals at the site.
The lock may be terminated by killing the lock process. Only the super user and the user who invoked lock may do so.
The -v option specifies verbose operation.
lock will not lock screens other than the current one if multiscreens are being used (see also mscreen(M) and multiscreen(M)). lock is also ineffective on X terminals for similar reasons; use scolock(XC) instead.