Module Outline

1. Introduction
2. Identify Automatically Started System Processes
3. Guided Exercise
4. Control System Services
5. Guided Exercise
6. Key Takeaways
7. Resources
8. Graded Lab

Learning Objectives

After completing the work in this module you will be able to:

1. List system daemons and network services started by the systemd units.
2. Control system daemons and network services, using systemctl.

Control Services and Daemons (replace me)

The systemd Daemon

Core Features of systemd

• The boot process is much simpler compared to the older init process.
• Concurrent and parallel starting of processes allows faster boot speed.
• Processes are tracked using control groups, not by PIDs.
• Improved handling of boot and service dependencies.
• System snapshots and restore points
• Crashed services can be restarted.
• Low memory footprint
• journald module for event logging

Describing Service Units

• .service units: Used to start frequently accessed daemons.
• .socket units: Represent inter-process communication (IPC) sockets that systemd should monitor.
• .path units: Used to delay the activation of a service until a specific file system change occurs.

Listing Service Units

Viewing Service States

Verifying the Status of a Service

Guided Exercise

Identify Automatically Started System Processes

Control System Services

Check the Status of a Service

Note:

Starting a Service

Note: Starting a service does not keep it running if the system reboots. The service must also be enabled.

Stopping a Service

Restarting a Service

Reloading a Service

List Unit Dependencies

Masking a Service

Enabling Services at Boot

Guided Exercise

Control System Services

Key Takeaways

• systemd is the first process that runs on the system and spawns all following processes.
• systemd enables faster reboot times and easier management of services.
• The systemctl command is used to start, stop, reload, enable, and disable services.
• Reloading a service keeps the same PID and doesn't terminate connections.
• The systemctl status command is used to determine the status of system daemons and network services.
• The systemctl list-dependencies command lists all service units upon which a specific service unit depends.
• systemd can mask a service unit so that it does not run even to satisfy dependencies.

Resources

• How To Use Systemctl to Manage Systemd Services and Units
• What are the Steps of the Linux Boot Process?
• systemd on Linux 2: systemctl commands

Graded Lab

Control Services and Daemons