Configure i3-wm lock screen to allow user switching

Here's a detailed article on using i3-wm with multiple users in Linux Mint 22 Cinnamon, focusing on i3-lock and dmil3-lock.

Introduction

i3-wm is a popular tiling window manager for Linux. It offers a highly customizable and efficient desktop environment. In a multi-user system, it's essential to provide support for multiple users while maintaining the benefits of i3-wm. This article will guide you through setting up i3-wm with multiple users in Linux Mint 22 Cinnamon, focusing on i3-lock and dmil3-lock.

Prerequisites

Before we begin, ensure you have the following prerequisites:

1. A fresh installation of Linux Mint 22 Cinnamon
2. User accounts created (sudo useradd -m username)
3. i3 and i3-lock installed (sudo apt-get install i3 i3-lock)

Configuring i3 for Multiple Users

By default, i3 is configured in the user's home directory at ~/.config/i3/. To support multiple users, we need to centralize the configuration.

1. Create a group for i3 configurations: sudo groupadd i3
2. Change the ownership of the i3 configuration directory to the group: sudo chgrp -R i3 ~/.config/i3/
3. Change the permissions of the i3 configuration directory to be writable by the group: sudo chmod -R g+w ~/.config/i3/
4. Each user should now belong to the i3 group: sudo usermod -aG i3 username
5. Move the user's local i3 configuration to the centralized location: mv ~/.config/i3/ ~username/.config/i3.local/

Configuring i3-lock for Multiple Users

By default, i3-lock uses the current user's configuration. To support multiple users, we need to modify the i3-lock script.

1. Backup the original i3-lock script: sudo mv /usr/bin/i3-lock /usr/bin/i3-lock.original
2. Create a new i3-lock script: sudo nano /usr/bin/i3-lock
3. Replace the content of the script with the following:

#!/bin/bash

# Get the current user
USER=$(whoami)

# Use the centralized i3 configuration
export XDG_CONFIG_HOME=/home/$USER/.config
export XDG_CONFIG_DIRS=/etc/xdg/i3

# Run i3-lock with the user's configuration
exec i3-lock

4. Save the file and make it executable: sudo chmod +x /usr/bin/i3-lock

Configuring dmil3-lock

dmil3-lock is a systemd service that locks the screen when the user logs out. To support multiple users, we need to modify the service file.

1. Open the dmil3-lock.service file: sudo nano /lib/systemd/system/dmil3-lock.service
2. Find the ExecStart line and modify it to use the user's configuration:

ExecStart=/usr/bin/i3-lock --lock-workspace 1 --no-output --no-bell --force-output --no-demand

3. Replace --no-demand with --user $USER:

ExecStart=/usr/bin/i3-lock --lock-workspace 1 --no-output --no-bell --force-output --user $USER

4. Save the file and reload the systemd daemon: sudo systemctl daemon-reload

Conclusion

With these changes, i3-wm and dmil3-lock should now support multiple users in Linux Mint 22 Cinnamon. Users can switch between their configurations without affecting others.

References

1. i3wm - ArchWiki
2. i3lock - ArchWiki
3. systemd.exec - systemd.man
4. dmil3-lock - ArchWiki