- Create new user:useradd [name]- Create new user with a default home directory:useradd --create-home [name]- Create new user with specified shell:useradd --shell [/path/to/shell] [name]- Create new user belonging to additional groups (mind the lack of whitespace):useradd --groups [group1,group2] [name]- Create new system user without a home directory:useradd --no-create-home --system [name]
When invoked without the -D option, the useradd command creates a new user account using the values specified on the command line plus the default values from the system. Depending on command line options, the useradd command will update system files and may also create the new user's home directory and copy initial files.
By default, a group will also be created for the new user (see -g, -N, -U, and USERGROUPS_ENAB).
The options which apply to the useradd command are:
-b, --base-dir BASE_DIR
If this option is not specified, useradd will use the base directory specified by the HOME variable in /etc/default/useradd, or /home by default.
-c, --comment COMMENT
-d, --home-dir HOME_DIR
-e, --expiredate EXPIRE_DATE
If not specified, useradd will use the default expiry date specified by the EXPIRE variable in /etc/default/useradd, or an empty string (no expiry) by default.
-f, --inactive INACTIVE
If not specified, useradd will use the default inactivity period specified by the INACTIVE variable in /etc/default/useradd, or -1 by default.
-g, --gid GROUP
If not specified, the behavior of useradd will depend on the USERGROUPS_ENAB variable in /etc/login.defs. If this variable is set to yes (or -U/--user-group is specified on the command line), a group will be created for the user, with the same name as her loginname. If the variable is set to no (or -N/--no-user-group is specified on the command line), useradd will set the primary group of the new user to the value specified by the GROUP variable in /etc/default/useradd, or 100 by default.
-G, --groups GROUP1[,GROUP2,...[,GROUPN]]]
-k, --skel SKEL_DIR
This option is only valid if the -m (or --create-home) option is specified.
If this option is not set, the skeleton directory is defined by the SKEL variable in /etc/default/useradd or, by default, /etc/skel.
If possible, the ACLs and extended attributes are copied.
-K, --key KEY=VALUE
Example: -K PASS_MAX_DAYS=-1 can be used when creating system account to turn off password ageing, even though system account has no password at all. Multiple -K options can be specified, e.g.: -K UID_MIN=100 -K UID_MAX=499
By default, the user's entries in the lastlog and faillog databases are resetted to avoid reusing the entry from a previously deleted user.
For the compatibility with previous Debian's useradd, the -O option is also supported.
By default, if this option is not specified and CREATE_HOME is not enabled, no home directories are created.
The default behavior (if the -g, -N, and -U options are not specified) is defined by the USERGROUPS_ENAB variable in /etc/login.defs.
This option is only valid in combination with the -u option.
-p, --password PASSWORD
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 policy.
System users will be created with no aging information in /etc/shadow, and their numeric identifiers are chosen in the SYS_UID_MIN-SYS_UID_MAX range, defined in /etc/login.defs, instead of UID_MIN-UID_MAX (and their GID counterparts for the creation of groups).
Note that useradd will not create a home directory for such an user, regardless of the default setting in /etc/login.defs (CREATE_HOME). You have to specify the -m options if you want a home directory for a system account to be created.
-R, --root CHROOT_DIR
-s, --shell SHELL
-u, --uid UID
See also the -r option and the UID_MAX description.
-Z, --selinux-user SEUSER
When invoked with only the -D option, useradd will display the current default values. When invoked with -D plus other options, useradd will update the default values for the specified options. Valid default-changing options are:
This option sets the HOME variable in /etc/default/useradd.
This option sets the EXPIRE variable in /etc/default/useradd.
This option sets the INACTIVE variable in /etc/default/useradd.
This option sets the GROUP variable in /etc/default/useradd.
This option sets the SHELL variable in /etc/default/useradd.
The system administrator is responsible for placing the default user files in the /etc/skel/ directory (or any other skeleton directory specified in /etc/default/useradd or on the command line).
You may not add a user to a NIS or LDAP group. This must be performed on the corresponding server.
Similarly, if the username already exists in an external user database such as NIS or LDAP, useradd will deny the user account creation request.
It is usually recommended to only use usernames that begin with a lower case letter or an underscore, followed by lower case letters, digits, underscores, or dashes. They can end with a dollar sign. In regular expression terms: [a-z_][a-z0-9_-]*[$]?
On Debian, the only constraints are that usernames must neither start with a dash ('-') nor plus ('+') nor tilde ('~') nor contain a colon (':'), a comma (','), or a whitespace (space: ' ', end of line: '\n', tabulation: '\t', etc.). Note that using a slash ('/') may break the default algorithm for the definition of the user's home directory.
Usernames may only be up to 32 characters long.
The following configuration variables in /etc/login.defs change the behavior of this tool:
This setting does not apply to system users, and can be overridden on the command line.
GID_MAX (number), GID_MIN (number)
The default value for GID_MIN (resp. GID_MAX) is 1000 (resp. 60000).
The MAIL_DIR and MAIL_FILE variables are used by useradd, usermod, and userdel to create, move, or delete the user's mail spool.
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)
The default values for SUB_GID_MIN, SUB_GID_MAX, SUB_GID_COUNT are respectively 100000, 600100000 and 10000.
SUB_UID_MIN (number), SUB_UID_MAX (number), SUB_UID_COUNT (number)
The default values for SUB_UID_MIN, SUB_UID_MAX, SUB_UID_COUNT are respectively 100000, 600100000 and 10000.
SYS_GID_MAX (number), SYS_GID_MIN (number)
The default value for SYS_GID_MIN (resp. SYS_GID_MAX) is 101 (resp. GID_MIN-1).
SYS_UID_MAX (number), SYS_UID_MIN (number)
The default value for SYS_UID_MIN (resp. SYS_UID_MAX) is 101 (resp. UID_MIN-1).
UID_MAX (number), UID_MIN (number)
The default value for UID_MIN (resp. UID_MAX) is 1000 (resp. 60000).
useradd and newusers use this mask to set the mode of the home directory they create
It is also used by pam_umask as the default umask value.
The useradd command exits with the following values:
chfn(1), chsh(1), passwd(1), crypt(3), groupadd(8), groupdel(8), groupmod(8), login.defs(5), newusers(8), subgid(5), subuid(5), userdel(8), usermod(8).