Common Issues in Linux Servers

Server management is one of the most critical topics for system administrators and developers. Ensuring the stability of servers, improving performance, and maintaining security requires addressing various challenges. In this article, I’ll summarize the most common server problems and how to solve them.

1. Server Crash

Problem:

Server crashes can occur due to hardware failure, software bugs, or system overload.

Solution:

• Check server logs: Review /var/log/syslog or /var/log/messages.
• Analyze resource usage: Use htop, top, free -m, and df -h commands.
• Set up automatic backups: Regularly back up data to avoid loss.
• Use monitoring tools: Tools like Zabbix, Prometheus, or Nagios can provide real-time tracking.

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2. High CPU Usage

Problem:

Some processes or applications may cause the CPU to overload, slowing down the server.

Solution:

• Identify high-CPU processes with top or htop.
• Stop unnecessary services: systemctl stop [service-name]
• Optimize worker processes in Apache or Nginx.
• Consider upgrading server resources (RAM or CPU).

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3. High RAM Usage

Problem:

Excessive RAM usage can cause performance degradation or system crashes.

Solution:

• Check memory usage with free -m.
• Find memory-hungry processes using ps aux --sort=-%mem | head -10.
• Review and adjust swap memory configuration if needed.
• Close unnecessary applications or optimize system services.

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4. Disk Full Issue

Problem:

When disk space is full, new data can't be written, affecting server performance.

Solution:

• Check disk usage with df -h.
• Identify large files with du -sh /var/log/*.
• Clear old logs: rm -rf /var/log/*.gz
• Remove unnecessary backup or cache files.
• Use additional disks or cloud storage for large data.

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5. Network Connectivity Issues

Problem:

Slow or lost network connections can affect access to the server.

Solution:

• Test internet with ping google.com.
• Check interface configuration using ifconfig or ip a.
• Use traceroute to analyze the network path.
• Verify router and DNS settings.
• Review firewall or iptables rules.

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6. SSH Access Problems

Problem:

Loss of SSH access makes server management difficult.

Solution:

• Access the server via console or alternative methods to verify SSH settings.
• Check /etc/ssh/sshd_config for port and access configurations.
• Restart SSH service: systemctl restart sshd
• Review firewall rules: iptables -L
• Validate and reconfigure SSH key authentication.

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7. Security Vulnerabilities and Attacks

Problem:

Servers can be targeted by malware or cyberattacks, creating serious security risks.

Solution:

• Use strong passwords and SSH key authentication.
• Prevent brute-force attacks using fail2ban or iptables.
• Enable automatic updates (apt update && apt upgrade or yum update -y).
• Implement DDoS protection and apply firewall rules.

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8. Database Performance Issues

Problem:

Databases like MySQL or PostgreSQL may respond slowly under heavy load or inefficient queries.

Solution:

• Analyze active queries with SHOW PROCESSLIST;
• Optimize indexes using ANALYZE TABLE and OPTIMIZE TABLE.
• Use caching systems like Redis or Memcached.
• Upgrade hardware to improve RAM and disk I/O performance.