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:
CREATE_HOME (boolean)
Indicate if a home directory should be created by default for new
users.
This setting does not apply to system users, and can be overridden
on the command line.
GID_MAX (number), GID_MIN (number)
Range of group IDs used for the creation of regular groups by
useradd, groupadd, or newusers.
MAIL_DIR (string)
. . , .
MAIL_FILE (string)
Defines the location of the users mail spool files relatively to
their home directory.
The MAIL_DIR and MAIL_FILE variables are used by useradd, usermod, and
userdel to create, move, or delete the user's mail spool.
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.
PASS_MAX_DAYS (number)
. , . , -1 ( ).
PASS_MIN_DAYS (number)
. . , -1 ( ).
PASS_WARN_AGE (number)
. , , . , .
SYS_GID_MAX (number), SYS_GID_MIN (number)
Range of group IDs used for the creation of system groups by
useradd, groupadd, or newusers.
SYS_UID_MAX (number), SYS_UID_MIN (number)
Range of user IDs used for the creation of system users by useradd
or newusers.
UID_MAX (number), UID_MIN (number)
Range of user IDs used for the creation of regular users by useradd
or newusers.
UMASK (number)
The file mode creation mask is initialized to this value. If not
specified, the mask will be initialized to 022.
useradd and newusers use this mask to set the mode of the home
directory they create
It is also used by pam_umask as the default umask value.
USERGROUPS_ENAB (boolean)
If set to yes, userdel will remove the user's group if it contains
no more members, and useradd will create by default a group with
the name of the user.
/etc/passwd
/etc/shadow
/etc/group
/etc/gshadow
/etc/default/useradd
/etc/skel/
,
/etc/login.defs
useradd , :
0
1
2
3
4
UID ( -o)
6
9
10
12
13
chfn(1), chsh(1), passwd(1), crypt(3), groupadd(8), groupdel(8),
groupmod(8), login.defs(5), newusers(8), userdel(8), usermod(8).
04/09/2012 useradd(8)