usermod(8) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | CAVEATS | CONFIGURATION | FILES | SEE ALSO | COLOPHON

USERMOD(8)             System Management Commands             USERMOD(8)

NAME         top

       usermod - modify a user account

SYNOPSIS         top

       usermod [options] LOGIN

DESCRIPTION         top

       The usermod command modifies the system account files to reflect
       the changes that are specified on the command line.

OPTIONS         top

       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, --badnames
           Allow names that do not conform to standards.

       -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. 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.

           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.

           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 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. 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
           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.

       -P, --prefix PREFIX_DIR
           Apply changes in the PREFIX_DIR directory and use the
           configuration files from the PREFIX_DIR directory. 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
           The path 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.

           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 users 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 users 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 users 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 users 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
           The new SELinux user for the user's login.

           A blank SEUSER will remove the SELinux user mapping for user
           LOGIN (if any).

CAVEATS         top

       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
       platforms 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         top

       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.

       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         top

       /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         top

       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).

COLOPHON         top

       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 2021-08-27.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2021-08-14.)  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 4.8.1             08/27/2021                     USERMOD(8)

Pages that refer to this page: 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)