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useradd - Unix, Linux Command
NAME
useradd - create a new user or update default new user informationSYNOPSIS
| Tag | Description |
|---|---|
|
useradd [options] LOGIN
useradd -D useradd -D [options] | |
DESCRIPTION
When invoked without the -D option, the useradd command creates a new user account using the values specified on the command line and 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. The version provided with Red Hat Linux will create a group for each user added to the system by default.
OPTIONS
The options which apply to the useradd command are:
| Tag | Description |
|---|---|
| -c, --comment COMMENT | |
| Any text string. It is generally a short description of the login, and is currently used as the field for the user’s full name. | |
| -b, --base-dir BASE_DIR | |
| The default base directory for the system if -d dir is not specified. BASE_DIR is concatenated with the account name to define the home directory. If the -m option is not used, BASE_DIR must exist. | |
| -d, --home HOME_DIR | |
| The new user will be created using HOME_DIR as the value for the user’s login directory. The default is to append the LOGIN name to BASE_DIR and use that as the login directory name. The directory HOME_DIR does not have to exist but will not be created if it is missing. | |
| -e, --expiredate EXPIRE_DATE | |
| The date on which the user account will be disabled. The date is specified in the format YYYY-MM-DD. | |
| -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. The default value is -1. | |
| -g, --gid GROUP | |
| The group name or number of the user’s initial login group. The group name must exist. A group number must refer to an already existing group. /etc/default/useradd. | |
| -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. The default is for the user to belong only to the initial group. | |
| -h, --help | |
| Display help message and exit. | |
| -M | The user’s home directory will not be created, even if the system wide settings from /etc/login.defs is to create home dirs. |
| -m, --create-home | |
| The user’s home directory will be created if it does not exist. The files contained in SKEL_DIR will be copied to the home directory if the -k option is used, otherwise the files contained in /etc/skel will be used instead. Any directories contained in SKEL_DIR or /etc/skel will be created in the user’s home directory as well. The -k option is only valid in conjunction with the -m option. The default is to not create the directory and to not copy any files. | |
| -l | Do not add the user to the last login log file. This is an option added by Red Hat. |
| -n | A group having the same name as the user being added to the system will be created by default. This option will turn off this Red Hat Linux specific behavior. When this option is used, users by default will be placed in whatever group is specified in /etc/default/useradd. If no default group is defined, group 1 will be used. |
| -K, --key KEY=VALUE | |
|
Overrides /etc/login.defs defaults (UID_MIN, UID_MAX, UMASK, PASS_MAX_DAYS and others).
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 Note: -K UID_MIN=10,UID_MAX=499 doesn’t work yet. | |
| -o, --non-unique | |
| Allow the creation of a user account with a duplicate (non-unique) UID. | |
| -p, --password PASSWORD | |
| The encrypted password, as returned by crypt(3). The default is to disable the account. | |
| -r | This flag is used to create a system account. That is, a user with a UID lower than the value of UID_MIN defined in /etc/login.defs and whose password does not expire. Note that useradd will not create a home directory for such an user, regardless of the default setting in /etc/login.defs. You have to specify -m option if you want a home directory for a system account to be created. This is an option added by Red Hat |
| -s, --shell SHELL | |
| The name of the user’s login shell. The default is to leave this field blank, which causes the system to select the default login shell. | |
| -u, --uid UID | |
| The 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 default is to use the smallest ID value greater than 999 and greater than every other user. Values between 0 and 999 are typically reserved for system accounts. | |
| -Z, --selinux-user SEUSER | |
| The SELinux user for the user’s login. The default is to leave this field blank, which causes the system to select the default SELinux user. | |
Changing the default values
When invoked with the -D option, useradd will either display the current default values, or update the default values from the command line. The valid options are
| Tag | Description |
|---|---|
| -b HOME_DIR | |
| The initial path prefix for a new user’s home directory. The user’s name will be affixed to the end of HOME_DIR to create the new directory name if the -d option is not used when creating a new account. | |
| -e EXPIRE_DATE | |
| The date on which the user account is disabled. | |
| -f INACTIVE | |
| The number of days after a password has expired before the account will be disabled. | |
| -g, --gid GROUP | |
| The group name or ID for a new user’s initial group. The named group must exist, and a numerical group ID must have an existing entry. | |
| -s, --shell SHELL | |
| The name of the new user’s login shell. The named program will be used for all future new user accounts. | |
NOTES
The system administrator is responsible for placing the default user files in the
/etc/skel/
directory.
This version of useradd was modified by Red Hat to suit Red Hat user/group conventions.
CAVEATS
You may not add a user to a NIS group. This must be performed on the NIS server.
Similarly, if the username already exists in an external user database such as NIS, useradd will deny the user account creation request.
FILES
| Tag | Description |
|---|---|
| /etc/passwd | |
| User account information. | |
| /etc/shadow | |
| Secure user account information. | |
| /etc/group | |
| Group account information. | |
| /etc/gshadow | |
| Secure group account information. | |
| /etc/default/useradd | |
| Default values for account creation. | |
| /etc/skel/ | |
| Directory containing default files. | |
| /etc/login.defs | |
| Shadow password suite configuration. | |
EXIT VALUES
The useradd command exits with the following values:
| Tag | Description |
|---|---|
| 0 | success |
| 1 | can’t update password file |
| 2 | invalid command syntax |
| 3 | invalid argument to option |
| 4 | UID already in use (and no -o) |
| 6 | specified group doesn’t exist |
| 9 | username already in use |
| 10 | can’t update group file |
| 12 | can’t create home directory |
| 13 | can’t create mail spool |
SEE ALSO
chfn(1), chsh(1), passwd(1), crypt(3), groupadd(8), groupdel(8), groupmod(8), login.defs(5), userdel(8), usermod(8).