What command lists the state of all service unit files?

The command that lists the state of all service unit files is the one that utilizes systemctl with the appropriate options for unit files focusing on services. The purpose of this command is to display information about each unit file's state, which can be either enabled, disabled, static, or masked, among others. This provides system administrators with a clear overview of what services are available, their configurations, and their current statuses.

By using the flag "--type=service," it specifically filters the output to show only service unit files, allowing for a more concise view that is particularly useful when managing system services.

The other options do not pertain to service unit files: mounting filesystems, checking swap usage, or partitioning disks do not relate to managing or listing service states in the system service management context.