Linux adduser and addgroup commands
The adduser command can also be used to add an existing user to an existing group.
How to use adduser and addgroup
adduser and addgroup add users and groups to the system according to command line options and configuration information in /etc/adduser.conf. They are friendlier front ends to the low-level tools like useradd, groupadd and usermod programs, by choosing policy-conformant UID and GID values, creating a home directory with skeletal configuration, running a custom script, and other features.
There are five major ways to use adduser and addgroup can run in one of five modes:
Add a normal user
If called with one non-option argument and without the --system or --group options, adduser adds a normal user.
adduser chooses the first available UID from the range specified for normal users in the configuration file. The UID can b overridden with the --uid option.
The range specified in the configuration file may be overridden with the --firstuid and --lastuid options.
By default, each user in a GNU/Linux system is given a corresponding group with the same name. User groups allow group writable directories to be easily maintained by placing the appropriate users in the new group, setting the set-group-ID bit in the directory, and ensuring that all users use a umask of 002. If this option is turned off by setting USERGROUPS to no, all users' GIDs are set to USERS_GID. Users' primary groups can also be overridden from the command line with the --gid or --ingroup options to set the group by id or name, respectively. Also, users can be added to one or more groups defined in adduser.conf either by setting ADD_EXTRA_GROUPS to 1 in adduser.conf, or by passing --add_extra_groups on the command line.
adduser creates a home directory subject to DHOME, GROUPHOMES, and LETTERHOMES. The home directory can be overridden from the command line with the --home option, and the shell with the --shell option. The home directory's set-group-ID bit is set if USERGROUPS is yes so that any files created in the user's home directory have the correct group.
adduser will copy files from SKEL into the home directory and prompt for finger (gecos) information and a password. The gecos may also be set with the --gecos option. With the --disabled-login option, the account is created but will be disabled until a password is set. The --disabled-password option will not set a password, but login is still possible (for example with SSH (secure shell) RSA (Rivest, Shamir, Adelman) keys). To set up an encrypted home directory for the new user, add the --encrypt-home option.
If the file /usr/local/sbin/adduser.local exists, it will be executed after the user account is set up to do any local setup. The arguments passed to adduser.local are: "username uid gid home-directory".
The environment variable VERBOSE is set according to the following rules:
- if --quiet is specified
- if neither --quiet nor --debug is specified
- if --debug is specified
(The same applies to the variable DEBUG, but DEBUG is deprecated and will be removed in a later version of adduser).
Add a system user
If called with one non-option argument and the --system option, adduser adds a system user. If a user with the same name already exists in the system uid range (or, if the uid is specified, if a user with that uid already exists), adduser will exit with a warning. This warning can be suppressed by adding "--quiet".
adduser chooses the first available UID from the range specified for system users in the configuration file (FIRST_SYSTEM_UID and LAST_SYSTEM_UID). To have a specific UID, you can specify it using the --uid option.
By default, system users are placed in the "nogroup" group. To place the new system user in an already existing group, use the --gid or --ingroup options. To place the new system user in a new group with the same ID, use the --group option.
A home directory is created by the same rules as for normal users. The new system user has the shell /bin/false (unless overridden with the --shell option), and have logins disabled. Skeletal configuration files are not copied.
Add a user group
If adduser is called with the --group option and without the --system option, or addgroup is called, a user group is added.
A GID will be chosen from the range specified for system GIDS in the configuration file (FIRST_GID, LAST_GID). To override that mechanism, you can give the GID using the --gid option.
The group is created with no users.
Add a system group
If addgroup is called with the --system option, a system group is added.
A GID will be chosen from the range specified for system GIDS in the configuration file (FIRST_SYSTEM_GID, LAST_SYSTEM_GID). To override that mechanism, you can give the GID using the --gid option.
The group is created with no users.
Add an existing user to an existing group
If you run adduser with two non-option arguments, it adds existing user user to group group, if it exists.
adduser [--system] [--home DIR] [--shell SHELL] [--no-create-home] [--uid ID] [--firstuid ID] [--lastuid ID] [--ingroup GROUP | --gid ID] [--disabled-password] [--disabled-login] [--gecos GECOS] [--add_extra_groups] [--encrypt-home] [--quiet] [--debug] [--force-badname] [--help|-h] [--version] [--conf FILE] user
addgroup [--system] [--quiet] [--debug] [--force-badname] [--help|-h] [--version] [--conf FILE] [--gid ID] group
adduser [options] user group
|Use FILE instead of /etc/adduser.conf.
|Do not run passwd to set the password. The user won't be able to use her account until the password is set.
|Like --disabled-login, but logins are still possible (for example using SSH RSA keys), but not using password authentication.
|By default, user and group names are checked against the configurable regular expression NAME_REGEX (or NAME_REGEX_SYSTEM if --system is specified) specified in the configuration file. This option forces adduser and addgroup to apply only a weak check for validity of the name.
|Set the gecos field for the new entry generated. adduser will not ask for finger information if this option is given.
|When creating a group, this option forces the new groupid to be the given number. When creating a user, this option puts the user in that group.
|When combined with --system, a group with the same name and ID as the system user is created. If not combined with --system, a group with the given name is created. This is the default action if the program is invoked as addgroup.
|Display a help message, and exit.
|Use DIR as the user's home directory, rather than the default specified by the configuration file. If the directory does not exist, it is created and skeleton files are copied.
|Use SHELL as the user's login shell, rather than the default specified by the configuration file.
|Add the new user to GROUP instead of a user group or the default group defined by USERS_GID in the configuration file. This affects the users primary group. To add additional groups, see the add_extra_groups option.
|Do not create the home directory, even if it doesn't exist.
|Suppress informational messages, only show warnings and errors.
|Be verbose, which is most useful if you want to nail down a problem with adduser.
|Create a system user or group.
|Force the new userid to be the given number. adduser fails if the userid is already taken.
|Override the first uid in the range that the uid is chosen from (overrides FIRST_UID specified in the configuration file).
|Override the last uid in the range that the uid is chosen from ( LAST_UID ).
|Add new user to extra groups defined in the configuration file.
|Display version and Copyright information.
The file /etc/adduser.conf contains defaults for the programs adduser, addgroup, deluser and delgroup. Each line holds a single value pair in the form "option = value". Double or single quotes are allowed around the value, as is whitespace around the equals sign. Comment lines must have a hash sign ("#") in the first column.
The valid configuration options are:
|The login shell to be used for all new users. Defaults to /bin/bash.
|The directory where new home directories should be created. Defaults to /home.
|If this is set to yes, the home directories is created as "/home/[groupname]/user". Defaults to no.
|If this is set to yes, then the home directories created have an extra directory inserted that is the first letter of the loginname. For example: /home/u/user. Defaults to no.
|The directory from which skeletal user configuration files should be copied. Defaults to /etc/skel.
|Specify an inclusive range of UIDs from which system UIDs can be dynamically allocated. Default to 100 - 999. Please note that system software, such as the users allocated by the base-passwd package, may assume that UIDs less than 100 are unallocated.
|Specify an inclusive range of UIDs from which normal user's UIDs can be dynamically allocated. Default to 1000 - 29999.
|Specify an inclusive range of GIDs from which system GIDs can be dynamically allocated. Default to 100 - 999.
|Specify an inclusive range of GIDs from which normal group's GIDs can be dynamically allocated. Default to 1000 - 29999.
|If this is set to yes, then each created user will be given a group to use. If this is no, then each created user will be placed in the group whose GID is USERS_GID (see below). The default is yes.
|If USERGROUPS is no, then USERS_GID is the GID given to all newly-created users. The default value is 100.
|If set to a valid value (e.g., 0755 or 755), directories created have the specified permissions as umask. Otherwise, 0755 is used as default.
|If this is set to yes, then home directories for users with a group ( USERGROUPS=yes ) have the setgid bit set. This was the default setting for adduser versions previous to 3.13. Unfortunately, it has some bad side effects, so we no longer do this per default. If you want it nevertheless you can still activate it here.
|If set to a nonempty value, new users have quotas copied from that user. The default is empty.
|User and group names are checked against this regular expression. If the name doesn't match this regexp, user and group creation in adduser is refused unless --force-badname is set. With --force-badname set, only weak checks are performed. The default is the most conservative ^[a-z][-a-z0-9]*$. When --system is specified, NAME_REGEX_SYSTEM is used instead.
|Names of system users are checked against this regular expression. If --system is supplied and the name doesn't match this regexp, user creation in adduser is refused unless --force-badname is set. With --force-badname set, only weak checks are performed. The default is as for the default NAME_REGEX but also allowing uppercase letters.
|Files in /etc/skel/ are checked against this regex, and not copied to the newly created home directory if they match. This is by default set to the regular expression matching files left over from unmerged config files (dpkg-(old|new|dist)).
|Setting this to something other than 0 (the default) causes adduser to add newly created non-system users to the list of groups defined by EXTRA_GROUPS (below).
|This is the list of groups that new non-system users are added to. By default, this list is 'dialout cdrom floppy audio video plugdev users games'.
|The user exists as specified. This can have 2 causes: The user was created by adduser or the user was already present on the system before adduser was invoked. If adduser was returning 0, invoking adduser a second time with the same parameters as before also returns 0.
|Creating the user or group failed because it was already present with other UID/GID than specified. The username or groupname was rejected because of a mismatch with the configured regular expressions. adduser was aborted by a signal.
Or this code may be returned for other undocumented reasons, which in that case are printed to console. You may then consider to remove --quiet to make adduser more verbose.
|Default configuration file for adduser and addgroup
Creates a new user account, mynewuser.
adduser prompts you to assign a password for the user, and ask you for optional identifying information such as Full Name and Phone Number.
A home directory (by default, /home/mynewuser) is created for the new user, and a user-specific group, mynewuser, is created. The contents of the skeleton home directory, which by default is located at /etc/skel, is copied into the new home directory.
If the script /usr/local/sbin/adduser.local exists, it will be executed with the arguments username uid gid home-directory, where username is mynewuser, uid is mynewuser's user id, gid is mynewuser's group id, and home-directory is mynewuser's home directory.
adduser --home /home/mynewuserhome mynewuser
Creates the user account mynewuser, and creates their home directory at the location /home/mynewuserhome.
deluser — Remove a user from the system.
finger — List information about a user.
groupadd — Add a group to the system.
passwd — Change a user's password.
useradd — Add a user to the system.
userdel — Remove a user from the system.
usermod — Modify a user's account.