Difference between revisions of "Setting up a new user"

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(User creation and defaults: Fix some typos)
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By default, remote management cannot be done direct;y 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.  
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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:
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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:
  
 
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adduser -D --shell /bin/bash general
 
adduser -D --shell /bin/bash general
  
chpassw | echo "secret_new_general_user_password"
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echo "secret_new_general_user_password" | chpasswd
 
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Revision as of 16:02, 16 July 2021

The root account should be used only for local administrative purposes that require elevated access permissions.

This page shows how to create non-privileged user accounts. i.e. those used for daily work, including desktop usage and remote logins.

Overview

Creating user accounts provides users 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).

Creating a new user

Tango-dialog-warning.png
Warning: 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).



Regular user accounts can be created with:

# 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.


Only if elogind is not being used and running, then X users would need to be added to the video and input groups to be able to work with a graphical display.

adduser 'UserName' video
adduser 'UserName' input


If a user really must be allowed to have access to the root account, the <username> can be added to the wheel group, doas ("do as") may be installed, and the group "wheel" can be allowed to become root:

adduser -g "<username>" <username>
adduser <username> wheel
apk add doas
apk add nano
nano /etc/doas.conf
Tango-dialog-warning.png
Warning: It's recommended to not run complete applications, like editors, as root just to modify administrative files.


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


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 -d "${NEWUSER}" $NEWUSER
echo "$NEWUSER ALL=(ALL) ALL" > /etc/sudoers.d/$NEWUSER && chmod 0440 /etc/sudoers.d/$NEWUSER


The new user gets listed in

Contents of /etc/passwd

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

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

Options

adduser

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)
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.

addgroup

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

Legacy

Common permission groups

(Taken from https://git.alpinelinux.org/alpine-baselayout/tree/group)

  • disk:x:6:root,adm needed only for use vith virtual machines and access to other partitions.
  • lp:x:7:lp needed for printing services and printers management.
  • wheel:x:10:root Administrator group, members can use sudo to run commands as root if enabled in the sudo configuration.
  • floppy:x:11:root Backward compatible group. Use only if access to special external devices is needed.
  • audio:x:18: Needed for audio listening and management of sound volume as normal user.
  • cdrom:x:19: For access to CD/DVD/BR writers and mounting DVD, BR or CD rom disk as normal user.
  • dialout:x:20:root Needed for dialing private connections and use of modems as normal user.
  • tape:x:26:root Needed if you're planning to use special devices for backup. Rare. Ususally used only on servers.
  • video:x:27:root For usage of cameras, more than one GPU special features, as normal user.
  • netdev:x:28: For network connections management as normal user.
  • kvm:x:34:kvm Only if a normal user will manage virtual machines via a GUI. Rare. Ususally used only on servers.
  • games:x:35: Needed if you want to play games. Especially if sharing scores between users.
  • cdrw:x:80: Needed to write RW-DVD, RW-BR or RW-CD disk on a disk writing device.
  • apache:x:81: Needed if you do development as normal user and want to publish locally on web server.
  • usb:x:85: Needed to access to special usb devices. Deprecated group.
  • users:x:100:games Needed if you plan to use common files for all users. Mandatory for 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

Note that those users are created with minimal privilege settings.

User management and system access

By default, a newly created user will not have enough privileges for most desktop purposes.

To add newly created users to groups that may come in handy for desktop useage, you run this command as root:

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