Troubleshooting Common Issues with Your VPS

For common VPS issues such as server crashes, unavailability, and resource depletion, provide detailed troubleshooting steps and solutions to enhance users’ self-solving abilities when encountering these problems.

1. VPS Crash

• Troubleshooting:
  • Check the provider’s control panel or notifications for ongoing maintenance or known issues.
  • Use the VPS’s remote console feature (e.g., VNC or KVM) to attempt logging into the system and check if it starts and runs normally.
  • Examine server log files (e.g., /var/log/messages or /var/log/syslog) for error messages that might have caused the crash.
• Solution:
  • If it’s a provider issue, contact support for details and estimated recovery time.
  • If the system fails to boot, it could be due to configuration errors or disk damage; try repairing the boot process or restoring from backups.
  • Address specific problems identified in the logs, such as updating faulty drivers, optimizing memory usage, or handling high-load processes.

2. Unable to Access VPS

• Troubleshooting:
  • Verify the local network environment is normal and use ping to test the connection to the VPS IP address.
  • Confirm the VPS’s network settings are correct, including firewall rules, security group policies, and port listening states.
  • If it’s a website service, ensure domain name resolution points correctly to the VPS IP and DNS changes have taken effect.
• Solution:
  • For local network issues, switch networks or contact your ISP for assistance.
  • Adjust VPS network settings by opening necessary ports or modifying overly strict firewall rules.
  • Ensure DNS resolution is correct; flush local DNS cache if needed and retry.

3. Resource Exhaustion

• Troubleshooting:
  • Log in to the VPS and use commands like top, htop, or vmstat to view CPU, memory, disk space, and I/O resource usage.
  • Identify any processes that abnormally consume resources, such as malware or memory-leaking applications.
• Solution:
  • For high CPU or memory usage, optimize application configurations, limit resource-hungry processes, or upgrade the VPS configuration for more resources.
  • If disk space is low, delete unnecessary files, optimize databases, schedule regular disk defragmentation, and consider increasing disk capacity.
  • To relieve high I/O pressure, adjust read-write strategies at the application layer or adopt SSD storage devices for better performance.

4. VPS Performance Degradation

• Troubleshooting:
  • Continuously monitor CPU, memory, disk I/O, and network bandwidth usage using tools like top, iotop, or iftop.
  • Check if there are large amounts of unused temporary files, log files, or other useless data occupying significant disk space.
  • Investigate whether there are too many zombie or idle processes that may consume system resources.
• Solution:
  • For CPU or memory bottlenecks, optimize code logic, reduce unnecessary computations, or allocate less memory; limit or optimize configurations for resource-intensive services.
  • Clear disk space, delete unnecessary files, compress or archive old logs, and plan disk partitions and storage structures rationally.
  • Terminate or optimize zombie and idle processes to ensure effective utilization of system resources.

5. VPS Under DDoS Attack

• Troubleshooting:
  • Observe abnormal growth in network traffic and use tools like iftop or netstat to see if there are numerous unexpected connection requests.
  • Check server logs for a large number of access errors, login failures, or other suspicious activity records.
• Solution:
  • Enable the VPS provider’s built-in DDoS protection service or deploy dedicated DDoS defense software.
  • Set appropriate filtering rules in the firewall or security groups to block malicious traffic from specific IPs or regions.
  • Temporarily disable attacked services or websites until the attack subsides, then re-enable them.

6. Frequent System Reboots

• Troubleshooting:
  • Examine system logs for error messages or warnings causing automatic restarts.
  • Check hardware health, especially for potential faults in memory and hard drives.
• Solution:
  • Fix related issues according to error messages in logs, e.g., kernel panics, software conflicts, etc.
  • Contact the VPS provider promptly to replace faulty hardware if needed.
  • Regularly update system patches and drivers to prevent restarts caused by software defects.

7. Database Issues

• Troubleshooting:
  • Log into the database and check its running state; for MySQL, use SHOW PROCESSLIST; to view current threads.
  • Inspect database error logs for entries about crashes, connection timeouts, or query failures.
  • Verify that there is sufficient disk space, particularly in the partition storing database data.
• Solution:
  • For database connectivity issues, possibly optimize the database connection pool configuration or increase system resources for supporting more concurrent connections.
  • If queries are inefficient, optimize SQL statements, add indexes, or design table partitioning based on business requirements.
  • If disk space is insufficient, clean up unneeded data, expand database storage space, or perform regular database maintenance and optimization.

8. SSH Connection Failure

• Troubleshooting:
  • Check local SSH client configuration, ensuring key files and passwords are set correctly.
  • Attempt to ping the VPS’s IP address to confirm network connectivity.
  • Check the status of the SSH service on the VPS, e.g., via systemctl status sshd (for systems based on Systemd).
  • Review the /var/log/auth.log or /var/log/secure log files for detailed information about SSH login failures.
• Solution:
  • Ensure local network and firewall allow SSH connections; temporarily close the local firewall for testing if necessary.
  • Verify VPS’s SSH service configuration, making sure it listens on the correct IP address and port, and rectify any configuration errors.
  • Restart the SSH service if accidentally stopped: systemctl start sshd or service sshd start.
  • Validate that SSH key pairs are correctly configured and that VPS’s sshd_config file settings meet expectations.

9. Severe Network Latency or Packet Loss

• Troubleshooting:
  • Use the ping command to check round-trip time and packet loss rate to the target server.
  • Utilize the traceroute or mtr tool to trace the network path and identify which node might be causing latency or packet loss issues.
  • Check your VPS provider’s network status for any congestion or node failures.
• Solution:
  • If the issue is with the VPS provider, contact their support to report the problem and inquire about any ongoing network issues or maintenance.
  • Consider changing the geographical location or data center of your VPS to a region closer to your target users.
  • For internal application networking problems, optimize network configurations such as adjusting routing rules to reduce unnecessary hops.

10. Application Crashes or Abnormal Behavior

• Troubleshooting:
  • Examine the error logs of the application itself, which typically record crash reasons and stack traces.
  • Use commands like ps or systemctl status to view the running status of the application.
  • Analyze system resource monitoring data (e.g., CPU, memory, disk I/O) to see if resource exhaustion is leading to program crashes.
• Solution:
  • Identify the root cause in the application error logs; if it’s a code bug, fix the code or update to a stable version.
  • Adjust system resource allocation to ensure critical applications have enough memory and CPU.
  • For long-running services, consider writing robust daemon scripts that can automatically restart the service after a crash.

11. File System Integrity Damage

• Troubleshooting:
  • Run the fsck command to check if the file system is damaged.
  • Inspect system logs for error messages related to the file system.
  • Use df -hT to view file system types and usage on each partition.
• Solution:
  • If file system damage is found, promptly run fsck and follow its prompts to repair it, but before doing so, back up important data.
  • Ensure your server has stable power supply and appropriate cooling measures, as power fluctuations and overheating can lead to hard drive damage and file system errors.
  • Conduct regular disk checks and file system maintenance, along with backing up data to prevent such occurrences.

12. Memory Leak Issues

• Troubleshooting:
  • Use top, htop, or free -m commands to monitor memory usage in real-time; a continuously rising memory usage without release may indicate a memory leak.
  • Perform a deep analysis of the application, checking log files for memory overflow error messages.
  • Employ memory analysis tools (like Valgrind or gdb) to detect specific locations of memory leaks.
• Solution:
  • Identify the application causing memory leaks and fix memory management issues within its code.
  • If immediate fix isn’t possible, try restarting the affected service or the entire system to release memory.
  • Increase VPS memory configuration, though this is only a temporary solution; fundamentally, the memory leak problem should still be resolved.

13. Frequent System Hangs or Slow Response

• Troubleshooting:
  • Use iotop to check if disk I/O operations are overly frequent.
  • Use vmstat or mpstat to inspect if the CPU is under excessive competition.
  • Review system logs for warnings or error messages indicating resource constraints.
• Solution:
  • For high disk I/O issues, optimize disk read/write operations, such as by planning data storage structures more efficiently, reducing unnecessary disk read/writes, or upgrading to faster storage solutions like SSDs.
  • If due to high CPU utilization, analyze and optimize the processes or services causing high loads, or upgrade the VPS’s CPU configuration.
  • For overall resource strain, improve performance by limiting resource use for non-core services, optimizing application configurations, etc.

14. Security Events (such as Intrusions, Virus Infections) 

• Troubleshooting:
  • Use security scanning tools (like ClamAV, rkhunter) to check if the system is infected.
  • Examine system logs for signs of abnormal logins, file modifications, or background processes indicative of security threats.
  • Collect and analyze security events using firewalls and intrusion detection systems.
• Solution:
  • Upon discovering viruses or malware, immediately isolate infected files or directories and clean them using security tools.
  • Update the system and all applications to their latest versions to fix known security vulnerabilities.
  • Strengthen system security, including installing and enabling firewalls, opening only necessary service ports, enhancing account and password management, and enabling SSH key verification.
  • For already compromised systems, it’s recommended to restore from a clean backup after removing malware and fixing security holes to prevent residual backdoors.

15. System Hangs or Unresponsive

• Troubleshooting:
  • Try remotely logging into the VPS console to see if the system interface can be accessed.
  • Examine system logs for Kernel Panic, deadlock, or other information leading to system freeze.
  • Confirm hardware status, such as CPU, memory, or disk functioning properly.
• Solution:
  • If it’s a hardware fault, contact the VPS provider to replace faulty components.
  • If it’s a system-level issue, reboot the system and after restarting, examine the logs to pinpoint the problem and apply corresponding fixes or optimizations.
  • If the system frequently hangs without cause, inspect scheduled tasks, system configurations, and software compatibility issues.

16. Incorrect System Time

• Troubleshooting:
  • Use the date or hwclock command to check if the system time is accurate.
  • Check if the NTP service is running correctly and has successfully synchronized with the network time.
• Solution:
  • Start or restart the NTP service to sync network time, e.g., execute systemctl start ntpd (for CentOS) or systemctl start chronyd (for Ubuntu).
  • Ensure the VPS host has access to external time servers; manually sync with a time server using ntpdate if needed.
  • If synchronization consistently fails, verify firewall settings to make sure relevant ports are not blocked.

17. Missing Service Dependencies or Version Conflicts

• Troubleshooting:
  • When a service cannot start or runs abnormally, check the service startup logs, which often indicate missing dependencies or version mismatches of services or library files.
  • Use the ldd command to check the dynamic library dependencies of binary files.
• Solution:
  • Install missing dependency services or library files using commands like yum install (for RHEL/CentOS) or apt-get install (for Debian/Ubuntu).
  • Upgrade or downgrade conflicting software packages to suitable versions.
  • For complex dependencies, utilize automated dependency management tools (like Python’s pip, Node.js’s npm, etc.) to manage software packages and dependencies uniformly.

18. Sudden Decrease in System Disk Space

• Troubleshooting:
  • Use the df -h command to view disk space usage across partitions and identify the suddenly reduced partition.
  • Check the /var/log or other log directories for abnormally large log files.
  • Use the du -sh * command to list directory sizes one by one, finding large files or directories consuming significant space.
• Solution:
  • Delete or compress unnecessary large files, such as oversized log files.
  • Clean up unnecessary temporary files, caches, and old software packages, e.g., using apt-get clean or yum clean all in Linux.
  • If large disk space is required, consider expanding the disk space or migrating part of the data to other storage media.

19. Network Service Abnormalities (e.g., inaccessible web server, failed email sending)

•  Troubleshooting:
  • Check if the corresponding services are running correctly, such as Apache, Nginx, Postfix, etc.
  • Examine service logs like Apache’s error_log, nginx’s access_log and error_log, and Postfix’s maillog for specific error messages.
  • Use the netstat -tuln command to verify that the service ports are listening properly and firewall rules allow access to the relevant ports.
• Solution:
  • Fix issues based on errors found in the service logs, e.g., expired certificates, configuration errors.
  • Adjust firewall rules to open required service ports.
  • Verify DNS resolution is correct to ensure the domain points to the right IP address.

20. User Permission Issues

• Troubleshooting:
  • When encountering permission denied errors while executing commands or operations, check the current user’s permission level.
  • Inspect file or directory permission settings using commands like ls -l.
• Solution:
  • Use sudo or switch to the root user to execute tasks requiring higher privileges.
  • Adjust file or directory permissions with commands like chmod and chown to ensure necessary operation permissions.

21. Frequent Creation of Large Amounts of Invalid or Temporary Files

• Troubleshooting:
  • Use the find command to search temporary directories (such as /tmp) for excessive file generation.
  • Check logs related to services or applications for abnormal behavior creating temporary files.
  • Use the lsof command to identify processes opening large numbers of files.
• Solution:
  • Regularly clean up temporary folders or set up scheduled tasks for automatic cleaning.
  • Repair or configure related services or apps to control the number of generated temporary files.
  • If caused by an abnormal process, terminate or restart it, or further investigate why it generates so many temporary files.

22. DNS Resolution Problems

• Troubleshooting:
  • Test domain name resolution using nslookup or dig, comparing expected and actual results.
  • Check if the DNS server configuration on the VPS is correct and matches records at the DNS provider.
  • Confirm whether there are issues with the local computer’s DNS cache.
• Solution:
  • Update DNS records at the domain registrar or DNS hosting provider to ensure A records or CNAMEs point correctly.
  • If running an in-house DNS server on the VPS, inspect DNS server software configurations to ensure zone file contents are accurate.
  • Clear the local computer’s DNS cache to obtain the latest DNS resolution results.

23. System Resource Abuse from Mining Software

• Troubleshooting:
  • Use top, htop, or ps commands to view CPU and memory usage, looking for unknown or abnormally resource-consuming processes.
  • Check network traffic for unusual outbound traffic.
  • Utilize virus scanning tools to detect if the system has been infected with mining malware.
• Solutios:
  • Terminate mining processes and remove associated files, using antivirus software to clean malicious software.
  • Inspect and patch system vulnerabilities to prevent re-infection.
  • Strengthen server security measures, including updating system patches, disabling unnecessary ports and services, and enforcing stronger password policies.

24. Network Interface Errors or Misconfiguration

• Troubleshooting:
  • Use ifconfig or ip addr to view network interface status, confirming correct IP address, subnet mask, default gateway configurations.
  • Check the physical connection state of network interfaces, including switch port settings and virtualization platform network configurations.
  • Test external network connectivity with the ping command.
• Solution:
  • Reconfigure network interface parameters according to actual requirements.
  • Contact the host service provider to confirm the physical link is functioning correctly.
  • In a virtualized environment, you may need to adjust the configuration of virtual network devices.

25. Kernel Panic or System Crash

• Troubleshooting:
  • Review screen output during kernel panic or consult system logs for panic-related information.
  • Analyze dump files (if kernel core dump functionality is configured) to pinpoint the crash cause.
  • Update the kernel version or try rolling back to a previous stable version.
• Solution:
  • Install relevant kernel patches or driver updates based on panic information.
  • Adjust system configurations to avoid hardware or software conflicts that could lead to kernel panics.
  • If unable to identify the root cause clearly, seek professional support for diagnosis.

These scenarios represent only some of the potential issues that can occur on a VPS, and each requires detailed technical analysis and specific actions to resolve properly. Maintaining good operational practices and timely security updates significantly reduces the likelihood of these problems occurring.