Introduction
Ubuntu Server is a dependable and widely-adopted Linux distribution, but even the most reliable systems can face challenges that impact performance or disrupt operations. Understanding how to troubleshoot common issues is crucial for maintaining uptime and ensuring seamless functionality. In this guide, “Troubleshooting Common Issues on Ubuntu Server,” we’ll explore practical techniques to diagnose and resolve frequent problems, such as boot failures, SSH connectivity errors, network issues, and more. You’ll also learn how to utilize system logs effectively to pinpoint the root cause of problems and restore your server to optimal performance.
Previous articles:
01. Introduction to Ubuntu Server – SysOSX: AI & Cloud
02. How to Setup Your First Ubuntu Server: A Beginner’s Guide – SysOSX: AI & Cloud
03.Mastering the Linux Command Line for Ubuntu Server – SysOSX: AI & Cloud
04. Managing Users and Permissions on Ubuntu Server: A Comprehensive Guide – SysOSX: AI & Cloud
05. Networking Basics for Ubuntu Server: A Comprehensive Guide – SysOSX: AI & Cloud
06. Installing and Managing Software on Ubuntu Server: A Complete Guide – SysOSX: AI & Cloud
07.Patching and Updating Ubuntu Server: A Comprehensive Guide – SysOSX: AI & Cloud
08. Securing Your Ubuntu Server: Practical Steps for Hardening and Protection – SysOSX: AI & Cloud
09. Ubuntu server auditing and logging
10. System Monitoring Tools for Ubuntu Server: A Comprehensive Guide – SysOSX: AI & Cloud
11. Centralized Logging for ubuntu server: a must read guide – SysOSX: AI & Cloud
12. Audit and Compliance for Ubuntu Server: Best Practices – SysOSX: AI & Cloud
14. Host Multiple Websites on a single Ubuntu Server: Useful tips – SysOSX: AI & Cloud
15. Managing Storage and Disks on Ubuntu Server: Simple Guide – SysOSX: AI & Cloud
16. Setting Up File Sharing Services on Ubuntu Server: a complete guide – SysOSX: AI & Cloud
17. Setting Up a Secure Database Server on Ubuntu: MySQL vs. MariaDB – SysOSX: AI & Cloud
18. How to Configure and Use LVM on Ubuntu Server: A Comprehensive Guide – SysOSX: AI & Cloud
21. Getting Started with LXD: Install Containers with Ease + Cheat Sheet – SysOSX: AI & Cloud
22. Getting Started with Podman on Ubuntu Server: A complete guide – SysOSX: AI & Cloud
23. Deploying Ubuntu Server in the Cloud: A Step-by-Step Guide – SysOSX: AI & Cloud
24. Automating Ubuntu Server Setup with Ansible: A Practical Guide – SysOSX: AI & Cloud
25.Upgrading Ubuntu Server from 22.04 to 24.04: A Step-by-Step Guide – SysOSX: AI & Cloud
Table of Contents
Common Ubuntu Server Issues and How to Troubleshoot
1. Boot Problems
Boot issues can occur due to corrupted files, hardware failures, or configuration errors.
Symptoms:
- Server fails to boot and displays a blank screen or error messages.
- The GRUB menu is inaccessible or missing.
- Kernel panic errors appear during startup.
Troubleshooting Steps:
Step 1: Access GRUB Menu
Restart the server and hold down the Shift key (or Esc key for UEFI systems) to access the GRUB menu.
Step 2: Boot into Recovery Mode
Select Advanced Options > Recovery Mode to boot into a minimal environment for troubleshooting.
Step 3: Check System Logs
Inspect the system logs for errors related to the boot process:
sudo journalctl -b
Look for errors or warnings related to kernel modules, disk mounting, or services.
Step 4: Repair Broken Packages
Run the following commands to fix broken packages:
sudo apt update
sudo apt install --fix-broken
Step 5: Reinstall GRUB
If GRUB is corrupted, reinstall it:
sudo grub-install /dev/sda
sudo update-grub
Step 6: Check Disk Health
Use fsck to check and repair disk errors:
sudo fsck /dev/sda
2. SSH Errors
SSH errors can prevent remote access to the server, disrupting management and automation tasks.
Symptoms:
- Unable to connect to the server via SSH.
- “Connection refused” or “Permission denied” errors.
- SSH hangs or times out.
Troubleshooting Steps:
Step 1: Verify SSH Service
Ensure the SSH service is running:
sudo systemctl status ssh
If the service is inactive, start it:
sudo systemctl start ssh
Step 2: Check SSH Logs
Inspect the SSH logs for detailed error messages:
sudo tail -n 50 /var/log/auth.log
Common issues include:
- Authentication failures.
- IP address blocks due to fail2ban or firewall rules.
Step 3: Check Firewall Rules
Ensure the firewall allows SSH traffic:
sudo ufw allow OpenSSH
sudo ufw status
Step 4: Inspect SSH Configuration
Check for errors in the SSH configuration file:
sudo nano /etc/ssh/sshd_config
Restart SSH after making changes:
sudo systemctl restart ssh
Step 5: Verify Network Connectivity
Ensure the server is reachable:
ping <server-ip>
3. Network Connectivity Issues
Network issues can prevent the server from accessing the internet or communicating with other devices.
Symptoms:
- Unable to ping external websites or other servers.
- DNS resolution errors.
- Network interfaces are down or misconfigured.
Troubleshooting Steps:
Step 1: Check Network Interfaces
List active network interfaces:
ip a
If an interface is down, bring it up:
sudo ip link set <interface-name> up
Step 2: Check Logs for Network Errors
Inspect network-related logs for potential issues:
sudo journalctl -u systemd-networkd
Step 3: Verify IP Configuration
Check the server’s IP address, gateway, and DNS settings:
cat /etc/netplan/*.yaml
If the configuration is incorrect, edit the file and apply changes:
sudo nano /etc/netplan/*.yaml
sudo netplan apply
Example Netplan Configuration:
network:
version: 2
ethernets:
eth0:
dhcp4: true
Step 4: Test DNS Resolution
Verify DNS resolution:
nslookup google.com
If DNS resolution fails, update /etc/resolv.conf with valid DNS servers:
nameserver 8.8.8.8
nameserver 8.8.4.4
4. Disk Space Issues
Low disk space can cause applications to crash or prevent updates.
Symptoms:
- “No space left on device” errors.
- Server becomes unresponsive.
Troubleshooting Steps:
Step 1: Check Disk Usage
Use df to check disk usage:
df -h
Step 2: Identify Large Files
Find large files consuming disk space:
sudo du -ah / | sort -rh | head -n 10
Step 3: Check Log File Sizes
Log files can grow excessively large. Check /var/log for oversized logs:
sudo du -sh /var/log/*
Remove or archive old logs:
sudo rm -rf /var/log/*.gz
sudo rm -rf /var/log/*.log.old
Step 4: Extend Disk Space
If the disk is full, extend the volume (cloud platforms like AWS, Azure, and GCP allow resizing disks).
5. Package Installation Errors
Package installation errors can occur due to broken dependencies or repository issues.
Symptoms:
- “Unable to locate package” or “Dependency errors” during installation.
Troubleshooting Steps:
Step 1: Check Logs for Package Errors
Inspect apt logs for detailed errors:
sudo tail -n 50 /var/log/apt/history.log
Step 2: Update Package Index
Ensure the package index is up-to-date:
sudo apt update
Step 3: Fix Broken Dependencies
Run the following command to resolve dependency issues:
sudo apt install --fix-broken
Step 4: Add Missing Repositories
If a package is unavailable, add the required repository:
sudo add-apt-repository universe
sudo apt update
6. High CPU or Memory Usage
Excessive resource usage can cause performance degradation and slow response times.
Symptoms:
- Server becomes unresponsive.
- Applications crash or timeout.
Troubleshooting Steps:
Step 1: Monitor Resource Usage
Use top or htop to monitor CPU and memory usage:
top
Step 2: Check Logs for Application Errors
Inspect application-specific logs in /var/log for errors causing high resource usage.
Step 3: Identify Resource-Hungry Processes
Find processes consuming excessive resources:
ps aux --sort=-%cpu | head -n 10
ps aux --sort=-%mem | head -n 10
Step 4: Kill Unnecessary Processes
Terminate resource-hungry processes:
sudo kill <pid>
Using Logs for Troubleshooting
Logs are one of the most valuable tools when troubleshooting server issues. Here’s how to check logs for common problems:
- System Logs:
sudo journalctl -xeProvides detailed logs about system-level errors and warnings. - Authentication Logs:
sudo tail -n 50 /var/log/auth.logUseful for diagnosing SSH and login-related issues. - Application-Specific Logs:
Check/var/logfor application-specific logs (e.g., Apache, MySQL). - Kernel Logs:
sudo dmesgDisplays kernel-related messages, useful for hardware and boot issues.
Conclusion
Troubleshooting Ubuntu Server issues requires a systematic approach to diagnosing and resolving problems. In this guide, we covered:
- Resolving boot problems, SSH errors, and network connectivity issues.
- Fixing disk space and package installation errors.
- Using logs effectively to diagnose issues.
By following these steps and leveraging logs, you can identify and fix server problems efficiently, ensuring a stable and reliable Ubuntu Server environment.