How to Check Logs with journalctl

What this is

journalctl reads the systemd journal (system logs) on modern Linux servers.

What it is for

• Troubleshoot failed services
• See recent errors and warnings
• Follow logs live while restarting services

Prerequisites

• SSH access
• Often needs sudo to see all logs

Step-by-step

View recent system logs

sudo journalctl -n 100 --no-pager

Filter by service (example: nginx)

sudo journalctl -u nginx -n 100 --no-pager

Follow logs live

sudo journalctl -u nginx -f

How to stop: Ctrl+C

Logs since boot

sudo journalctl -b --no-pager

Search for errors

sudo journalctl -p err -n 100 --no-pager

Final verification

Restart a service and watch logs:

sudo systemctl restart nginx
sudo journalctl -u nginx -n 30 --no-pager

Conclusion

journalctl is one of the fastest ways to understand why a service failed on a systemd server.