Using loginctl (with examples)

The loginctl command is a powerful tool for managing the systemd login manager. It allows you to list and manipulate user sessions and properties. In this article, we will explore several different use cases of the loginctl command, along with code examples and explanations.

Use Case 1: Print all current sessions

To print all current sessions, you can use the list-sessions option:

loginctl list-sessions

Motivation: This use case can be helpful when you want to see all active user sessions on your system. It allows you to quickly identify the logged-in users and their session IDs.

Explanation: The list-sessions option lists all active user sessions on the system. It provides information such as session ID, user, seat, and the timestamp of the last activity.

Example Output:

SESSION  UID USER             SEAT  TTY
 19     1000 john.doe         seat0 tty2
 22     1001 jane.smith       seat1 tty3

Use Case 2: Print all properties of a specific session

To print all properties of a specific session, you can use the show-session option with the session ID:

loginctl show-session session_id --all

Motivation: This use case allows you to retrieve detailed information about a specific session. It can be useful for troubleshooting session-related issues or gathering session data for analysis.

Explanation: The show-session option displays properties of a specific session. By providing the session ID, you can retrieve detailed information such as user, seat, session type, active state, and more.

Example Output:

Id=session_id
User=john.doe
Name=session
Timestamp=Tue 2021-04-20 09:15:32 PDT
State=active

Use Case 3: Print all properties of a specific user

To print all properties of a specific user, you can use the show-user option with the username:

loginctl show-user username

Motivation: This use case allows you to obtain information about a specific user, such as their login sessions, session state, and seat assignment. It can be helpful for monitoring user activity or troubleshooting user-related issues.

Explanation: The show-user option displays properties of a specific user. By providing the username, you can retrieve information such as login sessions, session state, seat assignment, and more.

Example Output:

John Doe:
  Sessions: 19
  State: online
  Seat: seat0

Use Case 4: Print a specific property of a user

To print a specific property of a user, you can use the show-user option with the --property argument:

loginctl show-user username --property=property_name

Motivation: This use case allows you to retrieve a specific property of a user, such as their state or seat assignment. It can be useful when you only need to access a particular piece of information about a user.

Explanation: The show-user option, when combined with the --property argument, helps you retrieve a specific property of a user. By providing the username and the property name, you can quickly access the desired information.

Example Output:

State=online

Use Case 5: Execute a loginctl operation on a remote host

To execute a loginctl operation on a remote host, you can use the -H option followed by the hostname:

loginctl list-users -H hostname

Motivation: This use case is useful when you want to manage user sessions on a remote host without physically accessing it. It allows administrators to control and monitor user sessions on remote systems efficiently.

Explanation: By leveraging the -H option and specifying the hostname, you can execute loginctl commands on a remote host. This enables you to interact with the login manager of the remote system and retrieve information or perform actions remotely.

Example Output:

USER     SESSIONS
john.doe    19
jane.smith  22

With the examples provided above, you should now have a solid understanding of how to use the loginctl command to manage user sessions and properties. Whether you need to retrieve information about specific sessions or control user activity on remote hosts, loginctl is a versatile tool that can assist you in managing the systemd login manager efficiently.