USERMOD(8) System Management Commands USERMOD(8)
NAME
usermod - modify a user account
SYNOPSIS
usermod [options] LOGIN
DESCRIPTION
The usermod command modifies the system account files.
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.
-b, --badname
Allow names that do not conform to standards.
-c, --comment COMMENT
update the comment field of the user in /etc/passwd, which 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. If the current home directory does not
exist the new home directory will not be created.
-e, --expiredate EXPIRE_DATE
The date on which the user account will be disabled. The date is
specified in the format YYYY-MM-DD. Integers as input are
interpreted as days after 1970-01-01.
An input of -1 or an empty string will blank the account expiration
field in the shadow password file. The account will remain available
with no date limit.
This option requires a /etc/shadow file. A /etc/shadow entry will be
created if there were none.
-f, --inactive INACTIVE
defines the number of days after the password exceeded its maximum
age during which the user may still login by immediately replacing
the password. This grace period before the account becomes inactive
is stored in the shadow password file. An input of 0 will disable an
expired password with no delay. An input of -1 will blank the
respective field in the shadow password file. See shadow(5) for more
information.
This option requires a /etc/shadow file. A /etc/shadow entry will be
created if there were none.
-g, --gid GROUP
The name or numerical ID of the user's new primary 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.
The change of the group ownership of files inside of the user's home
directory is also not done if the home dir owner uid is different
from the current or new user id. This is a safety measure for
special home directories such as /.
-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 must exist.
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
moves the content of the user's home directory to the new location.
If the current home directory does not exist the new home directory
will not be created.
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
allows to change the user ID to a non-unique value.
This option is only valid in combination with the -u option. As a
user identity serves as key to map between users on one hand and
permissions, file ownerships and other aspects that determine the
system's behavior on the other hand, more than one login name will
access the account of the given UID.
-p, --password PASSWORD
defines a new password for the user. PASSWORD is expected to be
encrypted, as returned by crypt (3).
Note: Avoid this option on the command line 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, --remove
Remove the user from named supplementary group(s). Use only with the
-G option.
-R, --root CHROOT_DIR
Apply changes in the CHROOT_DIR directory and use the configuration
files from the CHROOT_DIR directory. Only absolute paths are
supported.
-P, --prefix PREFIX_DIR
Apply changes within the directory tree starting with PREFIX_DIR and
use as well the configuration files located there. This option does
not chroot and is intended for preparing a cross-compilation target.
Some limitations: NIS and LDAP users/groups are not verified. PAM
authentication is using the host files. No SELINUX support.
-s, --shell SHELL
changes the user's login shell. An empty string for SHELL blanks the
field in /etc/passwd and logs the user into the system's default
shell.
-u, --uid UID
The new 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.
The change of the user ownership of files inside of the user's home
directory is also not done if the home dir owner uid is different
from the current or new user id. This is a safety measure for
special home directories such as /.
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).
-v, --add-subuids FIRST-LAST
Add a range of subordinate uids to the user's account.
This option may be specified multiple times to add multiple ranges
to a user's account.
No checks will be performed with regard to SUB_UID_MIN, SUB_UID_MAX,
or SUB_UID_COUNT from /etc/login.defs.
-V, --del-subuids FIRST-LAST
Remove a range of subordinate uids from the user's account.
This option may be specified multiple times to remove multiple
ranges to a user's account. When both --del-subuids and
--add-subuids are specified, the removal of all subordinate uid
ranges happens before any subordinate uid range is added.
No checks will be performed with regard to SUB_UID_MIN, SUB_UID_MAX,
or SUB_UID_COUNT from /etc/login.defs.
-w, --add-subgids FIRST-LAST
Add a range of subordinate gids to the user's account.
This option may be specified multiple times to add multiple ranges
to a user's account.
No checks will be performed with regard to SUB_GID_MIN, SUB_GID_MAX,
or SUB_GID_COUNT from /etc/login.defs.
-W, --del-subgids FIRST-LAST
Remove a range of subordinate gids from the user's account.
This option may be specified multiple times to remove multiple
ranges to a user's account. When both --del-subgids and
--add-subgids are specified, the removal of all subordinate gid
ranges happens before any subordinate gid range is added.
No checks will be performed with regard to SUB_GID_MIN, SUB_GID_MAX,
or SUB_GID_COUNT from /etc/login.defs.
-Z, --selinux-user SEUSER
defines the SELinux user to be mapped with LOGIN. An empty string
("") will remove the respective entry (if any). Note that the shadow
system doesn't store the selinux-user, it uses semanage(8) for that.
--selinux-range SERANGE
defines the SELinux MLS range for the new account. Note that the
shadow system doesn't store the selinux-range, it uses semanage(8)
for that.
This option is only valid if the -Z (or --selinux-user) option is
specified.
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. On other operating systems it only uses utmp to
check if the user is logged in.
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:
LASTLOG_UID_MAX (number)
Highest user ID number for which the lastlog entries should be
updated. As higher user IDs are usually tracked by remote user
identity and authentication services there is no need to create a
huge sparse lastlog file for them.
No LASTLOG_UID_MAX option present in the configuration means that
there is no user ID limit for writing lastlog entries.
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. The parameter
CREATE_MAIL_SPOOL in /etc/default/useradd determines whether the
mail spool should be created.
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.
SUB_GID_MIN (number), SUB_GID_MAX (number), SUB_GID_COUNT (number)
If /etc/subuid exists, the commands useradd and newusers (unless the
user already have subordinate group IDs) allocate SUB_GID_COUNT
unused group IDs from the range SUB_GID_MIN to SUB_GID_MAX for each
new user.
The default values for SUB_GID_MIN, SUB_GID_MAX, SUB_GID_COUNT are
respectively 100000, 600100000 and 65536.
SUB_UID_MIN (number), SUB_UID_MAX (number), SUB_UID_COUNT (number)
If /etc/subuid exists, the commands useradd and newusers (unless the
user already have subordinate user IDs) allocate SUB_UID_COUNT
unused user IDs from the range SUB_UID_MIN to SUB_UID_MAX for each
new user.
The default values for SUB_UID_MIN, SUB_UID_MAX, SUB_UID_COUNT are
respectively 100000, 600100000 and 65536.
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
/etc/subgid
Per user subordinate group IDs
/etc/subuid
Per user subordinate user IDs
SEE ALSO
chfn(1), chsh(1), passwd(1), crypt(3), gpasswd(8), groupadd(8),
groupdel(8), groupmod(8), login.defs(5), subgid(5), subuid(5),
useradd(8), userdel(8).
shadow-utils 4.17.4 04/19/2025 USERMOD(8)
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