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. The inbuilt root account should be used only for local administrative purposes that require elevated access permissions. Diskless mode users may want to refer to the section Persistent Home directory.

User management

Creating regular or non-privileged user accounts provides users with their own $HOME directory and allows root account 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). New users can be created in the following 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 the below mentioned adduser command.

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.

For complete adduser usage, check out the busybox manpage, which can be installed with the busybox-doc package or view it online

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 to logout from a TTY and login to the newly created account.

Group management

To see what group(s) you belong to, use the following command:$ groups. To check what group(s) another user belongs to use:

$ groups '<username>'

To add a user '<username>' 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.

root account

The root account is the most privileged account on a Unix system. The "root" account has no security restrictions imposed upon it. When you are signed in as, or acting as "root", the shell prompt displays '#' as the last character. This is to serve as a warning to you of the absolute power of this account.

SSH root login

For security reasons, root account is provided with local log-in access only and SSH login is disabled by default. To change this, edit the file /etc/ssh/sshd_config and add PermitRootLogin yes. Restart the sshd service for the change to take effect immediately.

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, sudoedit can be used.

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 an admin user is created with either doas or sudo properly configured and tested thoroughly, root account can be disabled by locking it.

Warning: Do not lock your root without thoroughly testing 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

Wheel group

The wheel group provides a mechanism to grant users administrator-level privileges without them needing to log in as the root user directly. The doas utility must be installed and configured, so that members of the wheel group can execute commands that require root privileges without needing to know the root password.

Admin user

If a regular user is added to the wheel group, then that user can be considered as an Admin user. The setup-user script allows quick and simple setup of admin user accounts by adding the <username> to wheel group and installs doas package, if not already installed:

# setup-user -a <username>

To provide admin user privileges to an existing user, add him to the wheel group as follows:

# adduser <username> wheel

doas

doas is a simplified and lightweight utility that provides a way to execute commands as another user. Install the doas package:

# apk add doas

To allow the members of the wheel group to use root privileges with doas, the config file /etc/doas.d/doas.conf 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 a much larger package than its alternative i.e doas.

Sudo may be used as follows:

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

Here a custom user configuration file i.e /etc/sudoers.d/$NEWUSER is used to avoid having to deal with manually changing configuration files later during package upgrades.

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

Note: This option is not recommended, as reverting to an older .apkovl will also revert the files in home directory.

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

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 Privileged access to input devices (not recommended on Wayland desktops). seat Access to input and output devices via seatd. tape Needed to give a set of users access to a tape drive. video Access to video capture devices (like a webcam) and privileged access to GPU devices. 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 for desktop usage.

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

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, then users that want a graphical environment need to be added to the video and seat groups. Be warned that adding users to the video has some negative security concerns (See #15409).

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