GROUP(5)

NAME
group - format of the group permissions file

DESCRIPTION
The file </etc/group> consists of newline separated ASCII records, one per group, containing four colon ‘’: separated fields. These fields are as follows:
group
    Name of the group.
passwd
    Group's encrypted password.
gid The group's decimal ID.
member
    Group members.

The group field is the group name used for granting file access to users who are members of the group. The gid field is the number associated with the group name. They should both be unique across the system (and often across a group of systems) since they control file access. The passwd field is an optional encrypted password. This field is rarely used and an asterisk is normally placed in it rather than leaving it blank. The member field contains the names of users granted the privileges of group. The member names are separated by commas without spaces or newlines. A user is automatically in a group if that group was specified in their /etc/passwd entry and does not need to be added to that group in the /etc/group file.

YP/NIS INTERACTION
The /etc/group file can be configured to enable the YP/NIS group database. An entry whose name field consists of a plus sign (`+') followed by a group name, will be replaced internally to the C library with the YP/NIS group entry for the named group. An entry whose name field consists of a single plus sign with no group name following, will be replaced with the entire YP/NIS “group.byname” map.

If the YP/NIS group database is enabled for any reason, all reverse lookups (i.e., getgrgid()) will use the entire database, even if only a few groups are enabled. Thus, the group name returned by getgrgid() is not guaranteed to have a valid forward mapping.

FILES
/etc/group

SEE ALSO
crypt(3), getgrent(3), initgroups(3), passwd(1), passwd(5), setgroups(2), yp(4)

BUGS
The passwd(1) command does not change the group passwords.

HISTORY
A group file format appeared in AT&T UNIX. The YP/NIS functionality is modeled after SunOS and first appeared in FreeBSD 1.1.