|
HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|
|
NAME | SYNOPSIS | DESCRIPTION | OPTIONS | CAVEATS | CONFIGURATION | FILES | SEE ALSO | COLOPHON |
|
|
|
USERMOD(8) System Management Commands USERMOD(8)
usermod - modify a user account
usermod [options] LOGIN
The usermod command modifies the system account files.
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
Specifies the date on which the user account will be disabled.
The value can be specified as a date in the YYYY-MM-DD format
or as a number of days since 1970-01-01. The date is
interpreted using the UTC timezone.
An input of -1 or an empty string blanks the account
expiration field in the shadow password file. The account will
remain available with no expiration date.
This option requires the /etc/shadow file. If no entry exists
in the /etc/shadow file, the system will automatically create
one.
-f, --inactive INACTIVE
Defines the number of days after a password exceeds its
maximum age during which the user can still log in by
immediately changing their password. If the user does not
change their password within this period of time, their
account becomes inactive. This value is stored in the shadow
password file.
A value of 0 disables the account when the password expires,
with no delay.
A value of -1 empties the respective field in the shadow
password file, which means that the inactivity period is not
enforced.
This option requires the /etc/shadow file. If no entry exist
in the /etc/shadow file, the system will automatically create
one.
-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
empties 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.
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.
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.
/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
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).
This page is part of the shadow-utils (utilities for managing
accounts and shadow password files) project. Information about
the project can be found at
⟨https://github.com/shadow-maint/shadow⟩. If you have a bug report
for this manual page, send it to
pkg-shadow-devel@alioth-lists.debian.net. This page was obtained
from the project's upstream Git repository
⟨https://github.com/shadow-maint/shadow⟩ on 2025-08-11. (At that
time, the date of the most recent commit that was found in the
repository was 2025-08-10.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
shadow-utils 4.18.0 08/11/2025 USERMOD(8)
Pages that refer to this page: getsubids(1), newgidmap(1), newuidmap(1), passwd(1), pcap(3pcap), subgid(5), subuid(5), groupadd(8), groupdel(8), groupmems(8), groupmod(8), pwck(8), useradd(8), userdel(8)
|
HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|