num:name:leader:members

where num is a decimal integer, name and leader are printable strings excluding the characters ?, =, +, -, /, and :, and members is a comma-separated list of such strings. Such a line defines a user and a group with the given name; the group has a group leader given by leader and group members given by the user names in members. The leader field may be empty, in which case any group member is a group leader. The members field may be empty.

Lines beginning with # are ignored.

The num in a line is a number used internally by a file server; there should be no duplicate nums in the file. A negative num is special: a user with a negative num cannot attach to the file server. The file /adm/users itself is owned by user adm, having a negative num, and write protected to others, so it can only be changed via console commands.