group - group membership file
The /etc/group file contains for each group the following information:
o group name
o encrypted password
o numerical group ID
o a comma separated list of all users allowed in the group
For example, the entry for the sys group is:
This is an ASCII file. A ``#'' at the beginning of a line indicates a
comment. The ``#'' is only recognized at the beginning of a line, it
should not be used after the user list. The fields are separated by
colons; each group is separated from the next by a new-line. Except at
the beginning of each line, white-space is not ignored, thus in most
cases there should be no spaces e.g. in the user list. If the password
field is null, no password is demanded. A ``*'' in the password field
locks the entry.
This file resides in the /etc directory. Because of the encrypted
passwords, it can and does have general read permission and can be used,
for example, to map numerical group ID's to names.
If the NFS option is installed, a group file can have a line beginning
with a plus (+), which means to incorporate entries from the NIS group
database. There are two styles of + entries: All by itself, + means to
insert the entire contents of the NIS group database at that point; +name
means to insert the entry (if any) for name from the NIS database at that
point. If a + entry has a non-null password or group member field, the
contents of that field will override what is contained in the NIS
database. The numerical group ID field cannot be overridden.
A group file can also have a line beginning with a minus (-), these
entries are used to disallow group entries. There is only one style of -
entries: an entry that consists of -name means to disallow any
subsequent entry (if any) for name. These entries will be disallowed
regardless of whether the subsequent entry comes from the NIS or the
local group file.
For example, if the following entries
appear at the end of a group file, then the group oldproj will be ignored
if it appears after the entry -oldproj. Also, the group myproject will
have members bill and steve, and the password and group ID of the NIS
entry for the group myproject. All the groups listed in the NIS database
will be pulled in and placed after the entry for myproject.
crypt(3), newgrp(1M), passwd(1), passwd(4)
The passwd(1) command won't change group passwords.
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