usermod man page on Archlinux

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USERMOD(8)		  System Management Commands		    USERMOD(8)

       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

       -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

	   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.

       -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)

	   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.

	   You should make sure the password respects the system's password

       -R, --root CHROOT_DIR
	   Apply changes in the CHROOT_DIR directory and use the configuration
	   files from the CHROOT_DIR directory.

       -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 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 new SELinux user for the user's login.

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

       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, 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.

       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 user's mail spool.

       If MAIL_CHECK_ENAB is set to yes, they are also used to define the MAIL
       environment variable.

       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.

	   Group account information.

	   Secure group account information.

	   Shadow password suite configuration.

	   User account information.

	   Secure user account information.

       chfn(1), chsh(1), passwd(1), crypt(3), gpasswd(8), groupadd(8),
       groupdel(8), groupmod(8), login.defs(5), useradd(8), userdel(8).

shadow-utils		  05/25/2012			    USERMOD(8)

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