The “dm-tool” command in Linux is used to manage the display manager on a system running the Display Manager Control Protocol (DMC). A display manager is a program that provides a graphical login prompt for users to log in to the system, such as LightDM, GDM, KDM, XDM etc. DMC is a protocol that allows for the management of display managers over the network.
The dm-tool command can be used to perform various operations on the display manager, such as switching to the login screen, locking or unlocking the current session, switching to a specific user, and more. This command can be useful for automating certain tasks related to the display manager and for remotely controlling the display manager over a network connection.
It is important to note that dm-tool is not a default command in Linux, it comes as part of Display Manager Control Protocol (DMC) which is an optional package and need to be installed. Also, the dm-tool command is typically used in conjunction with a remote login service such as SSH or VNC.
dm-tool Command Examples
1. Show the greeter while keeping current desktop session open and waiting to be restored upon authentication by logged in user:
# dm-tool switch-to-greeter
2. Lock the current session:
# dm-tool lock
3. Switch to a specific user, showing an authentication prompt if required:
# dm-tool switch-to-user username session
4. Add a dynamic seat from within a running LightDM session:
# dm-tool add-seat xlocal name=value