How to use the command systemd-sysusers (with examples)

The systemd-sysusers command is a utility that allows users to create system users and groups. It reads configuration files in the sysusers.d directories and creates the specified system users and groups accordingly. This command is useful for system administrators who need to manage user and group creation in a systemd-based system.

Use case 1: Create users and groups from a specific configuration file

Code:

systemd-sysusers path/to/file

Motivation: Creating users and groups from a specific configuration file is useful when you want to define a custom set of users and groups for your system. By specifying a specific configuration file, you can tailor the user and group creation process based on your requirements.

Explanation:

• systemd-sysusers: The command to run the systemd-sysusers utility.
• path/to/file: The path to the specific configuration file from which users and groups will be created.

Example output:

Created user: johndoe
Created group: mygroup

Use case 2: Process configuration files and print what would be done without actually doing anything

Code:

systemd-sysusers --dry-run path/to/file

Motivation: Using the --dry-run option is helpful when you want to preview the changes that would be made without actually modifying the system. It allows you to verify the correctness of the configuration file and ensure that the intended users and groups will be created.

Explanation:

• --dry-run: The option that indicates the command should only simulate the user and group creation process without actually performing them.
• path/to/file: The path to the configuration file to be processed.

Example output:

Would create user: johndoe
Would create group: mygroup

Use case 3: Print the contents of all config files

Code:

systemd-sysusers --cat-config

Motivation: Printing the contents of all config files can be useful when you want to inspect the configuration files and understand how users and groups are defined in each file. This can provide insights into the overall user and group management setup of your system.

Explanation:

• --cat-config: The option that instructs the command to print the contents of all config files.

Example output:

# File: /etc/sysusers.d/10-example.conf
[Users]
u johndoe - "John Doe"
g mygroup - "My Group"

# File: /etc/sysusers.d/20-example.conf
[Users]
u janedoe - "Jane Doe"
g mygroup - "My Group"

Conclusion:

The systemd-sysusers command is a versatile utility for creating system users and groups based on configuration files. By utilizing different options, such as specifying a specific configuration file or using the --dry-run flag, administrators can have fine-grained control over the user and group creation process. Additionally, the --cat-config option allows users to inspect the contents of configuration files, providing insights into the overall system setup.