GROUP(5) File Formats and Configurations GROUP(5)
NAME
group - group file
DESCRIPTION
The
group file is a local source of group information. The
group file can
be used in conjunction with other group sources, including the
NIS maps
group.byname and
group.bygid, or group information stored on an LDAP
server. Programs use the
getgrnam(3C) routines to access this
information.
The
group file contains a one-line entry for each group recognized by the
system, of the form:
groupname:
password:
gid:
user-list where
groupname The name of the group. A string consisting of lower case
alphabetic characters and numeric characters. Neither a
colon (
:) nor a NEWLINE can be part of a
groupname. The
string must be less than
MAXGLEN-1, usually
8, characters
long.
gid The group's unique numerical ID (GID) within the system.
user-list A comma-separated list of users allowed in the group.
The maximum value of the
gid field is 2147483647. To maximize
interoperability and compatibility, administrators are recommended to
assign groups using the range of GIDs below 60000 where possible.
If the password field is empty, no password is demanded. During user
identification and authentication, the supplementary group access list is
initialized sequentially from information in this file. If a user is in
more groups than the system is configured for,
{NGROUPS_MAX}, a warning
will be given and subsequent group specifications will be ignored.
Malformed entries cause routines that read this file to halt, in which
case group assignments specified further along are never made. To prevent
this from happening, use
grpck(1B) to check the
/etc/group database from
time to time.
If the number of characters in an entry exceeds 2047, group maintenance
commands, such as
groupdel(8) and
groupmod(8), fail.
Previous releases used a group entry beginning with a `
+' (plus sign) or
`
-' (minus sign) to selectively incorporate entries from a naming service
source (for example, an NIS map or data from an LDAP server) for group.
If still required, this is supported by specifying
group: compat in
nsswitch.conf(5). The
compat source may not be supported in future
releases. Possible sources are
files followed by
ldap. This has the
effect of incorporating information from an LDAP server after the
group file.
EXAMPLES
Example 1: Example group File.
The following is an example of a
group file:
root::0:root stooges:q.mJzTnu8icF.:10:larry,moe,curly and the sample group entry from
nsswitch.conf:
group: files ldap With these entries, the group
stooges will have members
larry,
moe, and
curly, and all groups listed on the LDAP server are effectively
incorporated after the entry for
stooges.
If the
group file was:
root::0:root
stooges:q.mJzTnu8icF.:10:larry,moe,curly
+:
and the group entry from
nsswitch.conf:
group: compat all the groups listed in the
NIS group.bygid and
group.byname maps would
be effectively incorporated after the entry for stooges.
SEE ALSO
groups(1),
newgrp(1),
grpck(1B),
getgrnam(3C),
initgroups(3C),
unistd.h(3HEAD),
nsswitch.conf(5),
groupadd(8),
groupdel(8),
groupmod(8) System Administration Guide: Basic Administration February 17, 2023
GROUP(5)