Case Study: Upgrading a Contabo VPS Running Odoo from Ubuntu 20.04 to 22.04 LTS 

A Comprehensive Guide with Challenges and Troubleshooting

1. Introduction

This case study documents the process of upgrading a Contabo Virtual Private Server (VPS) running Odoo from Ubuntu 20.04 LTS (Focal Fossa) to Ubuntu 22.04 LTS (Jammy Jellyfish). The server's primary function is to host multiple Odoo instances within Docker containers for Coqui Cloud's clients.

2. Preparation

Before initiating the upgrade, several preparatory steps were taken:

• Backup: A full backup of the server was created, including the Odoo databases and configuration files. Additionally, a snapshot of the VPS was taken through the Contabo control panel.
• Tools: MobaXterm Professional Edition v23.6 was used to establish an SSH connection to the server. VNC access was also available through the Contabo control panel.
• Initial checks: Docker compatibility with Ubuntu 22.04 was verified, and Contabo's documentation was reviewed for any specific recommendations or warnings regarding OS upgrades.

3. Upgrade Process

The upgrade process was initiated using the do-release-upgrade command. Several prompts and decisions were encountered during the process:

• Additional SSHD: An additional SSH daemon was started on port 1022 as a fallback in case the primary SSH connection was lost.
• sources.list Rewrite: The upgrade process prompted to rewrite the /etc/apt/sources.list file to update the repository URLs for the new Ubuntu version.
• Service Restarts: Various services required restarts during the upgrade, including PostgreSQL, cron, and display managers. The PostgreSQL service was manually stopped before the libc6 upgrade and restarted afterward.

4. Challenges and Troubleshooting

Several challenges and errors were encountered during the upgrade process:

• "No valid mirror found" error: This error occurred during the initial stage, indicating that the system couldn't find a suitable repository mirror. Rewriting the sources.list file resolved this issue.
• Network interface changes: Numerous messages indicated network interface renaming and status changes, likely due to Docker container activity and network configuration updates.
• Postfix configuration: Errors related to a missing Postfix configuration file (/etc/postfix/main.cf) were observed. This will need to be addressed if Postfix is required.
• GDM/Automatic login errors: Errors related to the GNOME Display Manager (GDM) and automatic login were encountered, indicating a potential issue with the display manager configuration.
• "Too many open files" errors: These errors suggested a potential resource leak or misconfiguration related to file descriptor limits.
• Upgrade seemingly stuck: At certain points, the upgrade process seemed to hang or take an unusually long time for specific packages. Monitoring system resources and logs helped to identify and resolve these bottlenecks.

Troubleshooting involved monitoring system logs (/var/log/syslog), checking system resource usage (top, htop), and researching error messages online.

5. Post-Upgrade Tasks

After the upgrade completed, several post-upgrade tasks were performed:

• System updates and cleanup: Packages were updated using apt update and apt upgrade, and obsolete packages were removed with apt autoremove.
• Network configuration verification: Network connectivity was tested using ping, and DNS resolution was verified using resolvectl status.
• Docker and Odoo testing: Docker containers were checked for proper operation, and Odoo instances were thoroughly tested for functionality.
• Security updates and checks: Security updates were applied, and system logs were reviewed for any suspicious activity.
• Performance monitoring: System resource usage was monitored for any performance bottlenecks.
• Addressing remaining issues: The missing Postfix configuration file and potential GDM/automatic login issues will need further investigation.
• DNS configuration: The nmcli command-line tool was used to configure Google's public DNS servers (8.8.8.8 and 8.8.4.4) through NetworkManager.

6. Lessons Learned

The upgrade process highlighted the importance of:

• Thorough preparation: Creating backups and snapshots is crucial before any major upgrade.
• Careful monitoring: Monitoring system logs and resource usage during the upgrade helps to identify and address potential issues promptly.
• Troubleshooting skills: Being able to research error messages and troubleshoot problems is essential for a successful upgrade.
• Documentation: Documenting the upgrade process, including challenges and solutions, provides valuable reference for future upgrades.

7. Conclusion

The upgrade to Ubuntu 22.04 LTS was successfully completed, despite encountering various challenges along the way. The Odoo instances are now running on the updated system, and post-upgrade tasks have been performed to ensure stability, security, and performance.

This case study serves as a valuable resource for Coqui Cloud, documenting the upgrade process and providing insights for future upgrades. It demonstrates the importance of preparation, monitoring, troubleshooting, and documentation when performing major system upgrades.