Once a Linux system is set up and connected, the last job is keeping it running and keeping it safe. Almost everything that runs in the background is a service, everything those services do gets recorded in logs, and everything exposed to the network needs security. This final module ties the three together.
It starts with services: starting, stopping, enabling, and checking them
with systemctl. Next you'll learn to read logs
with journalctl and find the classic files under
/var/log to troubleshoot problems. Then you'll turn to
security: putting up a firewall with UFW, applying a few
easy tweaks that make a server harder to attack, and hardening OpenSSH.
Take care when changing firewall and SSH settings on a remote machine: a wrong rule can lock you out, so keep a second session open while you test. When you finish this module, you've completed the course, so put it all to work in the Projects.
Start, stop, restart, enable, and check the status of services on a systemd-based system using systemctl.
Read and filter the systemd journal with journalctl to see what your system and its services have been doing.
Find where logs live, read them with tail and dmesg, follow them live, and spot bad login attempts in the authentication log.
Apply five simple, high-impact changes that make a Linux server noticeably harder to attack.
Strengthen the service most servers expose to the network with must-have OpenSSH settings, so a stolen or guessed password isn't enough to get in.