Setting up a new user

This page shows how to create non-privileged user accounts. i.e. those used for daily work, including desktop use and remote logins, and how to grant admin access to such accounts if needed.

Overview

Creating user accounts provides users with their own $HOME directory and allows you (the root user) to limit the access those user accounts have to the operating system configuration files.

Using them increases security, because they limit possible actions and thus possible damage (even from accidental errors).

Note: If you are using a "diskless" or "data" disk mode installation, refer to the section Persistent Home directory before proceeding further.

Creating a new user

The root account should be used only for local administrative purposes that require elevated access permissions. Regular or non-privileged user accounts can be created in two ways:

setup-user

The setup-user script allows quick and simple setup of user accounts. To create a regular user account using the above script:

# setup-user

User will be prompted for options. This script uses adduser in the backend.

adduser

# adduser [-g "<Full Name>"] <username>

By default, adduser will:

• prompt you to set a password for the new user
• create a home directory in /home/<username>
• set the shell to the one used by the root account (ash by default)
• assign user ID and group ID starting at 1000
• set the GECOS (full name) field to "Linux User,,,"

Tip: The optional -g "<Full Name>" above sets the GECOS field. This can be very useful to specify. Setting this string - at least equal to the username - makes the user distinguishable, e.g. when they are listed at the login screen of a display manager.

Usage (from "man busybox"):

adduser [OPTIONS] USER [GROUP]

Create new user, or add USER to GROUP

     -h --home DIR           Home directory
     -g --gecos GECOS        GECOS field
     -s --shell SHELL        Login shell named SHELL by example /bin/bash
     -G --ingroup GRP        Group (by name)
     -S --system             Create a system user
     -D --disabled-password  Don't assign a password, so cannot login
     -H --no-create-home     Don't create home directory
     -u --uid UID            User id
     -k SKEL                 Skeleton directory (/etc/skel)

The new user gets listed at the last line:

Contents of /etc/passwd

root:x:0:0:root:/root:/bin/ash ... <username>:x:1000:1000:<username>:/home/<username>:/bin/ash

Now you should be able to issue the command exit and login to the newly created account.

Group management

To see what group(s) you belong to, use the following command:

$ groups

To add your user to a group (for e.g seat) you can use the following commands:

# adduser '<username>' seat

The above command is a variation of adduser.

To add your user to a group you can also use the following command:

Usage (from "man busybox"):

addgroup [-g GID] [-S] [USER] GROUP

Create a group or add a user to a group

    -g --gid GID    Group id
    -S --system     Create a system group

Note: You need to log out and log in again for the group change(s) to take effect.

Admin user

If a user really must be allowed to have access to the root account, the <username> must be added to the wheel group. Also ensure that doas is available.

wheel group

The setup-user script allows quick and simple setup of admin user accounts. To Create a new user as admin user, using the above script:

# setup-user -a <username>

The above command will create an admin user, by adding the user to wheel group and installs doas, if not already installed.

To add an existing user as admin user:

# adduser <username> wheel

After adding the user as to wheel group using adduser, remember to install and configure doas, if not already done.

doas

The doas command provides a way to perform commands as another user. It aims to be a simplified and lightweight replacement for sudo. As mentioned earlier, the setup-user script automatically installs doas package.

# apk add doas

You will want to allow members of the wheel group to use root privileges with doas. To do this, your doas config file should be as follows:

Contents of /etc/doas.d/doas.conf

# See doas.conf(5) and doas.d(5) for configuration details. # Configuration here may be overridden by /etc/doas.d/*.conf if files exist. # Uncomment to allow group "wheel" to become root. permit persist :wheel

sudo

Note: Sudo has been deprecated in favour of doas in Alpine Linux since v3.15.0

Sudo (su “do”) allows a system administrator to delegate authority to give certain users (or groups of users) the ability to run some (or all) commands as root or another user while providing an audit trail of the commands and their arguments.

The sudo package is an alternative to using the BSD-like doas, but is a much larger package.

It may be used as follows: adding a custom user configuration file to avoid having to deal with manually changing configuration files later during package upgrades.

# apk add sudo # NEWUSER='yourUserName' # adduser -g "${NEWUSER}" $NEWUSER # echo "$NEWUSER ALL=(ALL) ALL" > /etc/sudoers.d/$NEWUSER && chmod 0440 /etc/sudoers.d/$NEWUSER

Securing root account

It's recommended to not run complete applications, like editors, as root just to modify administrative files.

• Use doasedit from doasedit available in the testing repository. It can be safely installed by following the guidelines.
• If using sudo, use sudoedit.

These tools enables starting an editor with a temporary copy of a file, which overwrites the original file after the user modifies and saves it. For example, doasedit /etc/apk/lbu.conf

• Many desktop environments and file browsers support using admin:/// in their address bars, to access files through a local gvfs-admin mount.

Once doas or sudo is properly configured and tested thoroughly, root account can be disabled by locking it.

Warning: Do not lock your root without testing thoroughly your admin user with either doas or sudo.

To lock the root account you need to log into your root account and then lock it using the passwd command:

# passwd -l root

Home directory permissions

`adduser` creates home directories with permissions `rwxr-sr-x`. This makes the directory readable by all other users on the system. If you prefer to not allow other users to read your home directory, the permissions can be changed:

chmod o-rx <path-to-directory>

Tip: Multi-user collaboration

If --ingroup isn't set, (default) the new user is assigned a new GID that matches the UID. If the GID corresponding to a provided UID already exists, adduser will fail.

This ensures new users default to having a "user's private group" (UPG) as primary group. These allow the system to use a permission umask (002), which creates new files automatically as group-writable, but only by the user's private group. In special set-group-id (collaboration) directories, new files can be automatically created writable by the directory's group.

Persistent Home directory

If using a "diskless" or "data" disk mode installation, it's important to make the /home directory persistent:

• Either the /home filesystem needs to be mounted from a writable partition, or
• the /home directories have to be added to the lbu backup, and a new local backup needs to be committed after creating the user:

# lbu include /home # lbu commit

(Not recommended, as reverting to an older .apkovl will also revert the files in /home).

Common permission groups

The following groups are needed for certain operations on your system. The group names were taken from https://git.alpinelinux.org/alpine-baselayout/tree/group

Note: Refer Debian/wiki SystemGroups to understand about the security implications of all these groups.

adm Used for system monitoring tasks. disk Raw access to disks. Mostly equivalent to root access. lp Members of this group can enable and use printers. wheel Administrator group, members can use doas to run commands as root if enabled in the doas configuration. floppy Access to floppy drives and other removable (non-optical) drives (like USB flash drives). audio Direct access to sound hardware (the soundcard or a microphone). cdrom For access to disk writers and mounting DVD, BR or CD-ROM disk as normal user. dialout Full and direct access to serial ports. input Access to input devices. tape Needed to give a set of users access to a tape drive. video Access to video capture devices (like a webcam). netdev For network connections management as normal user. kvm Needed to use the KVM acceleration of virtual machines. games Access to some game software. cdrw Needed to write RW-DVD, RW-BR or RW-CD disk on a disk writing device. usb Needed to access special USB devices, deprecated group. users Needed if you plan to used common files for all users, mandatory as desktop usage.

Desktop usage

If setup-desktop is used to install your desktop environment elogind is up and running automatically. If you installed your desktop manually and facing difficulties in using desktop or if seatd is used, then users that want a graphical environment need to be added to the video and seat groups.

Refer #15409 to understand about the security concerns regarding the video group.

To add newly created users to groups that may come in handy for desktop usage, you can run the below command as root:

# for u in $(ls /home); do for g in disk lp input audio cdrom dialout video netdev games users; do addgroup $u $g; done;done

Please pay attention to the groups in above command and proceed only if you want to add all the users in your system to above groups.

See also

• Users and groups - Archwiki
• SystemGroups