systemctl status, journalctl, and systemd-analyze are 100% safe. They are âread-only.â However, be careful with sudo systemctl stop. If you stop a service like dbus or systemd-logind, your screen might freeze or you might get logged out!Weâve all heard it: âHave you tried restarting it?â Restart a service in Linux with systemctl.Unlike old-school Linux logs (which were scattered across dozens of text files), systemd keeps everything in one central, encrypted location.
Table of Contents
1. Systemctl
Some distributions (like minimal Debian installs) might not have coredumpctl installed by default. You can usually get it by running sudo apt install systemd-coredump.systemd-analyze critical-chain
Additionally, some apps canât start until other apps are finished. If App A waits for App B, it creates a chain.
- Active (running): Everything is great!
- Inactive (dead): The service is off. Maybe it crashed, or maybe you never turned it on.
- Failed: This is the red flag. systemd will usually give you a âMain PIDâ (Process ID) and a reason for the failure right there in the terminal.
The âturn it off and on againâ trick
In Linux, background apps are called services. If your system is not accepting SSH connections, you use systemctl to see whatâs happening under the hood.
- Kickstart a failed one:
sudo systemctl start ssh - Stop a lagging service:
sudo systemctl stop ssh - Reset:
sudo systemctl restart ssh - Disable a service (to speed up boot):
sudo systemctl disable ssh
2. Journalctl
When an app crashes, it doesnât just vanish. It usually screams an error message into the void. Journalctl is the tool that catches those screams and saves them in a âjournalâ for you to read later.If youâve spent any time in the Linux community, you know that systemd is a hot topic. Some people love it because it handles everything; others wish it didnât! But hereâs the reality: almost every major Linux distribution (like Ubuntu, Fedora, and Debian) uses it today.
Filtering the noise
To see a table of every app that has crashed on your system recently, use:đĄsystemd-analyze blame
Coredumpctl is like a forensic investigator. It lets you look at that memory âsnapshotâ to see what the app was doing right before it died.journalctl --since "2 hours ago"
3. Systemd-analyze
coredumpctl list
The âDetective Reportâ
journalctl -u ssh
But where to find those answers? systemd has built-in tools that help you troubleshoot issues with your system. If youâre just starting your Linux journey, I recommend exploring the following four tools.
sudo systemctl status ssh
I mean, before you try to fix something, you need to know if itâs actually broken.
4. Coredumpctl
coredumpctl info [PID]
Next time something feels âoffâ on your Linux machine, donât panic. Just remember: systemctl for the status, journalctl for the logs, systemd-analyze for the speed, and coredumpctl for the crash.
Listing the crashes
By using these systemd tools, youâve moved past the âIâll just reboot and hope for the bestâ stage. You can now see the status of your apps, read their logs, speed up your boot time, and investigate crashes like a seasoned Linux user.journalctl -xe
- -x: Adds âcatalogâ info (it explains the errors in plain English).
- -e: Jumps straight to the end of the log so you see the newest stuff first.
Run this command to see a ranked list of the slowest-starting apps:
Conclusion
If you just type journalctl, youâll see thousands of lines of code, most of it is boring stuff like âSystem time updated.â To be a good detective, you need to filter:Sometimes, an app doesnât just have an error, it crashes completely. In programmer terms, it âdumped its core.â This means the app threw its entire memory onto the floor and quit.
