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This guide walks you through upgrading your Debian 11 (Bullseye) system to Debian 12 (Bookworm).
Before you begin:
  • Backup all important data
  • Create a snapshot of your VPS
  • Ensure you have console access in case of issues

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Pre-Upgrade Preparation

1

Update Debian 11

Ensure your current system is fully updated:
sudo apt update && sudo apt dist-upgrade -y
2

Disable third-party repositories

Comment out or remove third-party repository entries in /etc/apt/sources.list and /etc/apt/sources.list.d/.

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Upgrade Process

1

Update sources list

Replace bullseye with bookworm:
sudo sed -i 's/bullseye/bookworm/g' /etc/apt/sources.list
2

Update package lists

sudo apt update
3

Upgrade packages

sudo apt upgrade -y
4

Perform distribution upgrade

sudo apt dist-upgrade -y
Follow any on-screen prompts to resolve conflicts.
5

Reboot

sudo reboot
6

Verify upgrade

After rebooting, check the new version:
lsb_release -a

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Post-Upgrade Steps

1

Re-enable third-party repositories

Update third-party repositories to their Debian 12 versions if available.
2

Clean up

Remove obsolete packages:
sudo apt autoremove
sudo apt clean
3

Verify services

Check that all essential services are running correctly.
If you encounter issues during upgrade, use the KVM Console to access your server and troubleshoot.