Proxmox

https://pve.proxmox.com/wiki/Upgrade_from_6.x_to_7.0

1. update packages:

apt update

apt upgrade

2. if error on apt upgrade: https://forum.proxmox.com/threads/pve-firmware-conflicts-firmware-linux-free.53806/

apt remove linux-image-amd64 && apt upgrade

3. upgrade up to last 6.4 proxmox:

apt update

apt dist-upgrade

4. just in case run upgrade check:

pve6to7

5. Update all Debian repository entries to Bullseye:

sed -i 's/buster\/updates/bullseye-security/g;s/buster/bullseye/g' /etc/apt/sources.list

6. Add the Proxmox VE 7 Package Repository (free)

echo "deb http://download.proxmox.com/debian/pve bullseye pve-no-subscription" > /etc/apt/sources.list.d/pve-install-repo.list

7. add:

sed -i -e 's/buster/bullseye/g' /etc/apt/sources.list.d/pve-install-repo.list

8. update apt (questions about maintainer versions - Y)

apt update

apt dist-upgrade