Provided by:
passwd_4.1.4.2+svn3283-3ubuntu5_i386 
CONFIGURATION
The following configuration variables in /etc/login.defs change the
behavior of this tool:
GID_MAX (number), GID_MIN (number)
Range of group IDs used for the creation of regular groups by
useradd, groupadd, or newusers.
MAX_MEMBERS_PER_GROUP (number)
Maximum members per group entry. When the maximum is reached, a new
group entry (line) is started in /etc/group (with the same name,
same password, and same GID).
The default value is 0, meaning that there are no limits in the
number of members in a group.
This feature (split group) permits to limit the length of lines in
the group file. This is useful to make sure that lines for NIS
groups are not larger than 1024 characters.
If you need to enforce such limit, you can use 25.
Note: split groups may not be supported by all tools (even in the
Shadow toolsuite). You should not use this variable unless you
really need it.
SYS_GID_MAX (number), SYS_GID_MIN (number)
Range of group IDs used for the creation of system groups by
useradd, groupadd, or newusers.
/etc/group
/etc/gshadow
/etc/login.defs
It is usually recommended to only use groupnames that begin with a
lower case letter or an underscore, followed by lower case letters,
digits, underscores, or dashes. They can end with a dollar sign. In
regular expression terms: [a-z_][a-z0-9_-]*[$]?
On Debian, the only constraints are that groupnames must neither start
with a dash ('-') nor contain a colon (':') or a whitespace (space:' ',
end of line: '\n', tabulation: '\t', etc.).
Groupnames may only be up to 32 characters long.
You may not add a NIS or LDAP group. This must be performed on the
corresponding server.
If the groupname already exists in an external group database such as
NIS or LDAP, groupadd will deny the group creation request.
groupadd , :
0
2
3
4
gid ( -o)
9
10
chfn(1), chsh(1), passwd(1), gpasswd(8), groupdel(8), groupmod(8),
login.defs(5), useradd(8), userdel(8), usermod(8).
04/09/2012 groupadd(8)