NAME
usermod - modify a user account
SYNOPSIS
usermod [options] LOGIN
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 users password file comment field. It is
normally modified using the chfn(1) utility.
-d, --home HOME_DIR
The users 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.
-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.
-g, --gid GROUP
The group name or number of the users new initial login group. The
group must exist.
-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 users home directory
name should probably be changed manually to reflect the new login
name.
-L, --lock
Lock a users password. This puts a ! in front of the encrypted
password, effectively disabling the password. You cant 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 users home directory to the new location.
This option is only valid in combination with the -d (or --home)
option.
-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 systems password
policy.
-s, --shell SHELL
The name of the users 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 users ID.
This value must be unique, unless the -o option is used. The value
must be non-negative. Values between 0 and 999 are typically
reserved for system accounts.
The users mailbox, and any files which the user owns and which are
located in the users home directory will have the file user ID
changed automatically.
The ownership of files outside of the users home directory must be
fixed manually.
-U, --unlock
Unlock a users password. This removes the ! in front of the
encrypted password. You cant 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 SELinux user for the users login. The default is to leave this
field the blank, which causes the system to select the default
SELinux user.
CAVEATS
You must make certain that the named user is not executing any
processes when this command is being executed if the users numerical
user ID, the users name, or the users 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 users 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/passwd
User account information.
/etc/shadow
Secure user account information.
SEE ALSO
chfn(1), chsh(1), passwd(1), crypt(3), gpasswd(8), groupadd(8),
groupdel(8), groupmod(8), login.defs(5), useradd(8), userdel(8).