usermod






usermod − modify a user account

usermod [options] LOGIN



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



     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.

     −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.










                             ‐2‐


     −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.










                             ‐3‐


     −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 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









                             ‐4‐


     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 FIRSTLAST
     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 FIRSTLAST
     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 FIRSTLAST
     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 FIRSTLAST
     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).










                             ‐5‐




     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.



     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.










                             ‐6‐


     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.











                             ‐7‐


     /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).