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Linux Troubleshooting Cheatsheet - System Fault Diagnosis Command Reference

Essential Linux troubleshooting commands covering CPU, memory, disk, and network. Organized by scenario for on-site diagnosis — just copy and use.

SysOps·20 commands·Last updated 2026-07-21
linux排障进程端口
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Process & Load 5

top -c
Real-time process and load view, -c shows full command
ps aux --sort=-%cpu | head
Sort by CPU to find top consumers
ps aux --sort=-%mem | head
Sort by memory to find memory hogs
kill -9 <pid>
Force kill, only after trying regular kill
uptime
Quick check of 1/5/15-minute load averages

Port & Network 5

ss -tlnp
List listening TCP ports and their processes
ss -tlnp | grep :8080
Check which process is using a specific port
curl -v http://127.0.0.1:8080
Verify local service reachability, see handshake details
ping -c 4 host
Test connectivity
dig +short example.com
Quick DNS resolution lookup

Disk & Memory 5

df -h
Check disk usage per partition
du -sh * | sort -rh | head
Find largest items in current directory
free -h
Check memory and swap usage
lsof +L1
Find deleted files still held by processes (disk full but no large file found)
iostat -x 1
Monitor disk I/O pressure, requires sysstat

Logs & Services 5

journalctl -u nginx -n 200 --no-pager
View recent systemd service logs
journalctl -f
Follow system logs in real time
systemctl status nginx
Check service status and recent log lines
tail -f /var/log/app.log
Follow application log file
dmesg -T | tail
View kernel messages for OOM and hardware errors

Tips

  • Disk shows full but no large file found — a process likely holds a deleted file. Use lsof +L1 to locate it, then restart the process.
  • kill sends SIGTERM by default for graceful shutdown — try regular kill first, only use kill -9 if stuck.
  • "Out of memory: Killed process" in dmesg means OOM, not a crash in the application itself.

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Official References

Commands are compiled from the official docs below. Click to verify the latest usage.

Maintained by LaoHand

Publicly updated on Jul 21, 2026, continuously proofread against official docs.

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