How to Check System Errors in /var/log

What this is

Many Linux services write traditional log files under /var/log (in addition to journalctl). This guide shows where to look.

What it is for

• Find errors when something fails
• Check web server logs, auth logs, system logs

Prerequisites

• SSH access
• sudo may be required

Step-by-step

Step 1) List /var/log

ls -la /var/log

Step 2) Common files by distro

• Ubuntu/Debian: /var/log/syslog, /var/log/auth.log
• RHEL-based: /var/log/messages, /var/log/secure

Step 3) Read the last 100 lines

sudo tail -n 100 /var/log/syslog
sudo tail -n 100 /var/log/auth.log

Step 4) Follow logs live

sudo tail -f /var/log/auth.log

Step 5) Search for keywords

sudo grep -i "error" /var/log/syslog | tail -n 50

Final verification

When troubleshooting a service, check its own logs too:

sudo ls -la /var/log/nginx
sudo tail -n 50 /var/log/nginx/error.log

Conclusion

/var/log is your classic “paper trail”. Combine it with journalctl for faster troubleshooting.