Upgrade Debian Linux 9 or 10 to Debian 11 for Olfeo virtual appliances running under VMware/Hyper-V.

We're going to upgrade from Debian 9 to Debian 11.
We'll do this gradually, starting with the upgrade
-> Debian 9 to Debian 10 and then
-> Debian 10 to Debian 11

Attention

The machines concerned must be upgraded in a non-production state, 
one by one, so as not to disrupt your company's network activity.

PROCEDURE

BACKUP THE APPLIANCE AND CHECK THE CURRENT DEBIAN VERSION

1. We start by backing up our virtual machine. A snapshot under VMware or Hyper-V is sufficient.
2. We then check which Debian version we are on by typing the following command: lsb_release -aResult under Debian 9 :Result under Debian 10 :
3. If you're in Debian 10, you can scroll down to the "Upgrade Debian 10 to Debian 11" section.

UPGRADE DEBIAN 9 TO DEBIAN 10

1. We start by updating our system :apt update
   apt upgrade
   apt full-upgrade
2. We then go to /etc/apt/source.list and replace "stretch" with "buster".
3. We rerun the previous commands to retrieve Debian 10 updates :apt update
   apt upgrade
   apt full-upgradeIf you come across this screen during the upgrade, you can select "Yes".
4. After the update and upgrade, we can reboot the machine :reboot
5. Check that we have upgraded to Debian 10 :lsb_release -a

UPGRADE DEBIAN 10 TO DEBIAN 11

1. We start by updating our system :apt update
   apt upgrade
   apt full-upgrade
2. We then go to /etc/apt/source.list, where we replace "buster" with "bullseye" and "buster/updates" with "bullseye-security".
   Our file should look like this:
3. We rerun the previous commands to retrieve the Debian 11 updates: apt update
   apt upgrade
   apt full-upgrade
4. Once the update and upgrade are complete, we run a command to clean up any unnecessary packages: apt autoremove -purge
5. We can now reboot the machine :reboot
6. Check that we have upgraded to Debian 11 :lsb_release -a

OLFEO SERVICES VERIFICATION

To check the status of Olfeo services.
We enter the Olfeo chroot:

chroot /opt/olfeo/chroot/

We then enter the following command:

./olfeo-status.sh

If any services are not started correctly, you can type the following command to restart the services:

./olfeo-stop.sh && ./olfeo-start.sh