Setting up a new user: Difference between revisions

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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.


Creating a user is an important step when first configuring a Linux system. Generally ''root'' account is used for administration only as it has access to the operating system and its configuration.
= Overview =


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


When Alpine Linux is first installed by default it comes with the user ''root'' with no password set. For security reasons it's always a good idea to either set a password to the user ''root'' or disabling the login to the user, which its why is suggested to run <code>[[setup-alpine]]</code> to change ''root'' password.
Using them increases security, because they limit possible actions and thus possible damage (even from accidental errors).


Creating an account allows it to have it's own $HOME directory and allows you to limit access to the configuration of the operating system for security reasons.
{{Warning|If you are using a '''"diskless" or "data" disk mode''' installation, refer to the section [[#Persistent Home directory|Persistent Home directory]] before proceeding further.}}


= Creating a new user =
= Creating a new user =


Using the command '''adduser''' will allow you to create a new user in the system.
The <code>root</code> 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 [[Alpine_setup_scripts#setup-user|setup-user]] script allows quick and simple setup of user accounts. To create a regular user account using the above script:
{{Cmd|# setup-user}}
 
User will be prompted for options. This script uses [[#adduser|adduser]] in the backend.
 
== adduser ==
{{Cmd|# adduser [-g "<Full Name>"] <username>}}
 
By default, <code>adduser</code> will:
* prompt you to set a password for the new user
* create a home directory in {{Path|/home/<username>}}
* set the shell to the one used by the <code>root</code> 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 <code>-g "<Full Name>"</code> 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"):
 
<pre><nowiki>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)
</nowiki></pre>
 
The new user gets listed at the last line:
{{Cat|/etc/passwd|<nowiki>
root:x:0:0:root:/root:/bin/ash
...
<username>:x:1000:1000:<username>:/home/<username>:/bin/ash
</nowiki>}}
 
Now you should be able to issue the command <code>exit</code> and login to the newly created account.
<br>
{{Note| If you used [[setup-desktop]] to install your desktop environment, you will be able to use your desktop without issues, as [[elogind]] is up and running automatically for you. In other cases, if you are facing difficulties your user may need to be added to certain [[#Group management|groups]]. }}
 
= Group management =
 
To see what group(s) you belong to, use the following command:
{{Cmd|$ groups}}
 
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 {{Issue|15409}} regarding security concerns.
 
To add your user to a group (for e.g '''video''' and '''seat''') you can use the following commands:
 
# adduser '<username>' video
# adduser '<username>' seat
 
The above command is a variation of [[#adduser|adduser]].
 
To add your user to a group you can also use the following command:
 
Usage (from "man busybox"):
 
<pre><nowiki>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
</nowiki></pre>
 
{{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 either [[#doas|doas]] or [[#sudo|sudo]] is available.
 
== wheel group ==
 
The [[Alpine_setup_scripts#setup-user|setup-user]] script allows quick and simple setup of admin user accounts. To Create a new user as admin user, using the above script:
 
{{Cmd|# setup-user -a <username>}}
 
The above command will create an admin user, by adding the user to wheel group and installs <code>{{Pkg|doas}}</code>, if not already installed.
 
To add an existing user as admin user:
{{Cmd| # adduser <username> wheel}}
 
After adding the user as to wheel group using <code>adduser</code>, remember to install and configure [[#doas|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|sudo]].
 
{{Cmd| # apk add {{Pkg|doas}} }}
You will want to allow members of the '''wheel''' group to use root privileges with <code>doas</code>. To do this, your <code>doas</code> config file should be as follows:
{{Cat|/etc/doas.d/doas.conf|<nowiki>
permit persist :wheel
</nowiki>
}}


{{Cmd|adduser <username>}}


It will prompt to set a password for the new user, by example let's create a new user with session name "test"
== sudo ==
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.


# adduser test
The <code>sudo</code> package is an alternative to using the BSD-like <code>doas</code>, but is a much larger package.
Changing password for test
New password:
Retype password:
passwd: password for test changed by root


The new user can be seen in
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


{{Cat|/etc/passwd|root:x:0:0:root:/root:/bin/ash
<br>
.
.
.
test:x:1000:1000:Linux User,,,:/home/test:/bin/ash}}


You can now ''exit'' and login to the new account.
= Securing root account =


== User management commands ==
It's recommended to '''not''' run complete applications, like editors, as root just to modify administrative files.
<br>
* [https://github.com/AN3223/scripts/blob/master/doasedit <code>doasedit</code>] or <code>sudoedit</code>([https://wiki.alpinelinux.org/wiki/Release_Notes_for_Alpine_3.15.0#Move_from_sudo_to_doas being deprecated in favour of <code>doas</code>]) 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, <code>sudoedit /etc/apk/lbu.conf</code>
* Many desktop environments and file browsers support using <code>admin:///</code> in their address bars, to access files through a local gvfs-admin mount.


Alpine at install comes only with busybox user management commands and the following are standar for all linux distributions


If no ''OPTIONS'' is set, by default when creating a new user, it will create a home directory in {{Path|/home/<username>}}, with the shell set that uses the ''root'' account (ash by default), user ID and group ID 1000+, and the GECOS field ''Linux User,,,''.
Once [[#doas]] or [[#sudo]] is properly configured and tested thoroughly, root account can be disabled by locking it.


=== adduser ===
{{Warning| Do not lock your root without testing thoroughly your [[#Admin user|admin user]] with either [[#doas]] or [[#sudo]].}}


Usage:
To lock the root account you need to log into your '''root''' account and then lock it using the <code>passwd</code> command: {{cmd|# passwd -l root}}


<pre><nowiki>adduser [OPTIONS] USER [GROUP]</nowiki></pre>
= Home directory permissions =


Create new user, or add USER to GROUP
`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:
 
{{Cmd| chmod o-rx <path-to-directory>}} 
 
{{Tip|Multi-user collaboration
If <nowiki>--ingroup</nowiki> 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 <code>/home</code> directory persistent
 
<br>
* Either the <code>/home</code> 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:
{{Cmd| # lbu include /home
# lbu commit
}} (Not recommended, as reverting to an older .apkovl will also revert the files in /home).
 
 
= Common permission groups =
 
{{Draft|Need to note a few security implications outlined on [https://wiki.debian.org/SystemGroups debian/wiki SystemGroups]}}
 
Groups are needed for certain operations on your system.
 
(Names taken from https://git.alpinelinux.org/alpine-baselayout/tree/group)
 
{{Cmd|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.}}
 
= Old newbie notes =
=== User creation and defaults ===
 
The following commands will set up root environment login, then assign a new password:
 
<pre><nowiki>
cat > /root/.cshrc << EOF
unsetenv DISPLAY || true
HISTCONTROL=ignoreboth
EOF
 
cp /root/.cshrc /root/.profile
 
echo "secret_new_root_password" | chpasswd
</nowiki></pre>
 
By default, remote management cannot be done directly with the root account. Because of SSH security we need to set up a remote connection account that will be used to switch to the root user via the su command, once connected.
 
Here's an example: create user named "remote" and a user named "general". We will set up a hardened, limited, user environment and create those two users:
 
<pre><nowiki>
mkdir -p /etc/skel/
 
cat > /etc/skel/.logout << EOF
history -c
/bin/rm -f /opt/remote/.mysql_history
/bin/rm -f /opt/remote/.history
/bin/rm -f /opt/remote/.bash_history
EOF


* --home DIR Home directory
cat > /etc/skel/.cshrc << EOF
*    --gecos GECOS GECOS field
set autologout = 30
*    --shell SHELL Login shell named SHELL by example /bin/bash
set prompt = "$ "
*    --ingroup GRP Group (by name)
set history = 0
*    --system Create a system user
set ignoreeof
*    --disabled-password Don't assign a password so cannot login in
EOF
*    --no-create-home Don't create home directory
*    --uid UID User id


Those options only work for newer versions:
cp /etc/skel/.cshrc /etc/skel/.profile


*  -k SKEL Skeleton directory (/etc/skel)
adduser -D --home /opt/remote --shell /bin/ash remote


One thing to note is that if <pre>--ingroup</pre> isn't set then the GID is assigned to match the UID. If the GID corresponding to the provided UID already exists adduser will fail.
echo "secret_new_remote_user_password" | chpasswd


=== addgroup ===
adduser -D --shell /bin/bash general


Usage:
echo "secret_new_general_user_password" | chpasswd
</nowiki></pre>


<pre><nowiki>addgroup [-g GID] [-S] [USER] GROUP</nowiki></pre>
{{Tip|"'''general'''" is the name of the user. That name MUST contain ONLY lowercase letters, NO spaces and NO symbols}}


Add a group or add a user to a group
To add newly created users to groups that may come in handy for desktop usage, you run this command as root:


* --gid GID  Group id
{{cmd|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}}
*  --system  Create a system group


Alpine base groups permissions, check for base layout package:
== See also ==


https://git.alpinelinux.org/alpine-baselayout/tree/group
* [https://wiki.archlinux.org/title/Users_and_groups Users and groups - Archwiki]


[[Category:Newbie]]
[[Category: System_Administration]]

Latest revision as of 06:31, 13 August 2024

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).

Warning: 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.

Note: If you used setup-desktop to install your desktop environment, you will be able to use your desktop without issues, as elogind is up and running automatically for you. In other cases, if you are facing difficulties your user may need to be added to certain groups.

Group management

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

$ groups

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 regarding security concerns.

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

# adduser '<username>' video
# 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 either doas or sudo 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.

# 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

permit persist :wheel


sudo

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.

  • doasedit or sudoedit(being deprecated in favour of doas) 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, sudoedit /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

This material is work-in-progress ...

Need to note a few security implications outlined on debian/wiki SystemGroups
(Last edited by Prabuanand on 13 Aug 2024.)

Groups are needed for certain operations on your system.

(Names 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 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.

Old newbie notes

User creation and defaults

The following commands will set up root environment login, then assign a new password: 

cat > /root/.cshrc << EOF
unsetenv DISPLAY || true
HISTCONTROL=ignoreboth
EOF

cp /root/.cshrc /root/.profile

echo "secret_new_root_password" | chpasswd

By default, remote management cannot be done directly with the root account. Because of SSH security we need to set up a remote connection account that will be used to switch to the root user via the su command, once connected.

Here's an example: create user named "remote" and a user named "general". We will set up a hardened, limited, user environment and create those two users: 

mkdir -p /etc/skel/

cat > /etc/skel/.logout << EOF
history -c
/bin/rm -f /opt/remote/.mysql_history
/bin/rm -f /opt/remote/.history
/bin/rm -f /opt/remote/.bash_history
EOF

cat > /etc/skel/.cshrc << EOF
set autologout = 30
set prompt = "$ "
set history = 0
set ignoreeof
EOF

cp /etc/skel/.cshrc /etc/skel/.profile

adduser -D --home /opt/remote --shell /bin/ash remote

echo "secret_new_remote_user_password" | chpasswd

adduser -D --shell /bin/bash general

echo "secret_new_general_user_password" | chpasswd
Tip: "general" is the name of the user. That name MUST contain ONLY lowercase letters, NO spaces and NO symbols

To add newly created users to groups that may come in handy for desktop usage, you run this 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

See also

Retrieved from "https://wiki.alpinelinux.org/w/index.php?title=Setting_up_a_new_user&oldid=27038"