usermod
modify a user account
see also :
chfn - chsh - passwd - gpasswd - groupadd - groupdel - groupmod - useradd - userdel
Synopsis
add an example, a script, a trick and tips
examples
source
usermod -G z,sudo z
chown z:z -R /sources/
chown z:z -R /cmd/
description
The
usermod command modifies the system account files to
reflect the changes that are specified on the command
line.
options
The options
which apply to the usermod command are:
-a,
--append
Add the user to the
supplementary group(s). Use only with the -G
option.
-c,
--comment COMMENT
The new value of the user's
password file comment field. It is normally modified using
the chfn(1) utility.
-d,
--home HOME_DIR
The user's new login
directory.
If the
-m option is given, the contents of the current
home directory will be moved to the new home directory,
which is created if it does not already exist.
-e,
--expiredate EXPIRE_DATE
The date on which the user
account will be disabled. The date is specified in the
format YYYY-MM-DD.
An empty
EXPIRE_DATE argument will disable the expiration of
the account.
This option
requires a /etc/shadow file. A /etc/shadow entry will be
created if there were none.
-f,
--inactive INACTIVE
The number of days after a
password expires until the account is permanently
disabled.
A value of 0
disables the account as soon as the password has expired,
and a value of -1 disables the feature.
This option
requires a /etc/shadow file. A /etc/shadow entry will be
created if there were none.
-g,
--gid GROUP
The group name or number of the
user's new initial login group. The group must exist.
Any file from
the user's home directory owned by the previous primary
group of the user will be owned by this new group.
The group
ownership of files outside of the user's home directory must
be fixed manually.
-G,
--groups
GROUP1[,GROUP2,...[,GROUPN]]]
A list of supplementary groups
which the user is also a member of. Each group is separated
from the next by a comma, with no intervening whitespace.
The groups are subject to the same restrictions as the group
given with the -g option.
If the user is
currently a member of a group which is not listed, the user
will be removed from the group. This behaviour can be
changed via the -a option, which appends the
user to the current supplementary group list.
-l,
--login NEW_LOGIN
The name of the user will be
changed from LOGIN to NEW_LOGIN. Nothing else
is changed. In particular, the user's home directory or mail
spool should probably be renamed manually to reflect the new
login name.
-L,
--lock
Lock a user's password. This
puts a '!' in front of the encrypted password, effectively
disabling the password. You can't use this option with
-p or -U.
Note: if you
wish to lock the account (not only access with a password),
you should also set the EXPIRE_DATE to 1.
-m,
--move-home
Move the content of the user's
home directory to the new location.
This option is
only valid in combination with the -d (or
--home) option.
usermod
will try to adapt the ownership of the files and to copy the
modes, ACL and extended attributes, but manual changes might
be needed afterwards.
-o,
--non-unique
When used with the
-u option, this option allows to change the
user ID to a non-unique value.
-p,
--password PASSWORD
The encrypted password, as
returned by crypt(3).
Note:
This option is not recommended because the password (or
encrypted password) will be visible by users listing the
processes.
The password
will be written in the local /etc/passwd or /etc/shadow
file. This might differ from the password database
configured in your PAM configuration.
You should make
sure the password respects the system's password policy.
-R,
--root CHROOT_DIR
Apply changes in the
CHROOT_DIR directory and use the configuration files
from the CHROOT_DIR directory.
-s,
--shell SHELL
The name of the user's new
login shell. Setting this field to blank causes the system
to select the default login shell.
-u,
--uid UID
The new numerical value of the
user's ID.
This value must
be unique, unless the -o option is used. The
value must be non-negative.
The user's
mailbox, and any files which the user owns and which are
located in the user's home directory will have the file user
ID changed automatically.
The ownership
of files outside of the user's home directory must be fixed
manually.
No checks will
be performed with regard to the UID_MIN,
UID_MAX, SYS_UID_MIN, or SYS_UID_MAX
from /etc/login.defs.
-U,
--unlock
Unlock a user's password. This
removes the '!' in front of the encrypted password. You
can't use this option with -p or
-L.
Note: if you
wish to unlock the account (not only access with a
password), you should also set the EXPIRE_DATE (for
example to 99999, or to the EXPIRE value from
/etc/default/useradd).
-Z,
--selinux-user SEUSER
The new SELinux user for the
user's login.
A blank
SEUSER will remove the SELinux user mapping for user
LOGIN (if any).
caveats
You must make certain that the named user is not executing any
processes when this command is being executed if the user's
numerical user ID, the user's name, or the user's home directory
is being changed. usermod checks this on Linux, but only
check if the user is logged in according to utmp on other
architectures.
You must change the owner of any crontab files or
at jobs manually.
You must make any changes involving NIS on the NIS server.
configuration
The following configuration variables in /etc/login.defs change
the behavior of this tool:
MAIL_DIR (string)
The mail spool directory. This is needed to manipulate the
mailbox when its corresponding user account is modified or
deleted. If not specified, a compile-time default is used.
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.
files
/etc/group
Group account information.
/etc/gshadow
Secure group account information.
/etc/login.defs
Shadow password suite configuration.
/etc/passwd
User account information.
/etc/shadow
Secure user account information.
see also
chfn ,
chsh , passwd , crypt,
gpasswd , groupadd , groupdel ,
groupmod , login.defs, useradd ,
userdel .