**🚨 Common Linux Server Issues & Quick Fixes 🚨** 

As a sysadmin or DevOps engineer, managing Linux servers can be challenging. Here’s a list of common issues and commands to resolve them efficiently: 

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### **1. Disk Space Running Out** 

**Fix**: 

- Check disk usage: `df -h` 

- Find large files: `du -sh /var/* | sort -rh` 

- Clean temp files: `sudo rm -rf /tmp/*` 

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### **2. High CPU Usage** 

**Fix**: 

- Monitor CPU usage: `top` 

- Terminate problematic process: `kill <PID>` 

- Analyze processes: `ps aux --sort=-%cpu` 

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### **3. Memory Issues** 

**Fix**: 

- Check memory usage: `free -h` 

- Identify memory-hogging processes: `ps aux --sort=-%mem` 

- Clear cache: `echo 3 > /proc/sys/vm/drop_caches` 

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### **4. Service Unavailable** 

**Fix**: 

- Check service status: `sudo systemctl status <service>` 

- Restart service: `sudo systemctl restart <service>` 

- Check logs: `sudo journalctl -u <service>` 

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### **5. Network Problems** 

**Fix**: 

- Test connectivity: `ping <ip>` 

- Check open connections: `netstat -tuln` 

- Verify firewall rules: `sudo ufw status` 

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### **6. Permission Errors** 

**Fix**: 

- Check permissions: `ls -l <file>` 

- Modify permissions: `sudo chmod 755 <file>` 

- Change ownership: `sudo chown user:group <file>` 

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### **7. Update Failures** 

**Fix**: 

- Clear package cache: `sudo apt clean` 

- Fix broken packages: `sudo apt --fix-broken install` 

- Update system: `sudo apt update && sudo apt upgrade -y` 

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### **8. Logs Consuming Space** 

**Fix**: 

- Compress logs: `sudo tar -czvf logs_archive.tar.gz /var/log/` 

- Configure log rotation: `sudo nano /etc/logrotate.conf` 

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### **9. SSH Access Issues** 

**Fix**: 

- Check SSH status: `sudo systemctl status sshd` 

- Restart SSH: `sudo systemctl restart sshd` 

- Check logs: `sudo tail -f /var/log/auth.log` 

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### **10. DNS Resolution Failure** 

**Fix**: 

- Check DNS config: `cat /etc/resolv.conf` 

- Test DNS resolution: `nslookup google.com` 

- Restart network: `sudo systemctl restart networking` 

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### **11. Time Synchronization Issues** 

**Fix**: 

- Check time sync status: `timedatectl status` 

- Manually sync time: `sudo ntpdate pool.ntp.org` 

- Restart NTP service: `sudo systemctl restart ntp` 

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### **12. Corrupted Filesystem** 

**Fix**: 

- Check filesystem integrity: `sudo fsck /dev/sdX` 

- Reinstall critical packages: `sudo apt-get install --reinstall coreutils` 

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### **13. User Quota Exceeded** 

**Fix**: 

- Check quotas: `repquota -a` 

- Modify user quotas: `edquota -u <username>` 

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### **14. Zombie Processes** 

**Fix**: 

- Identify zombie processes: `ps aux | grep 'Z'` 

- Kill parent process: `kill -9 <PPID>`