PBS 4 upgrade rollback

[di5cord20]

I successfully upgraded proxmox to v9. I then ran https://community-scripts.github.io/ProxmoxVE/scripts?id=pbs4-upgrade but am still on PBS 3.0-2, but my repositories are now pointing to trixie. I then reviewed https://pbs.proxmox.com/wiki/Upgrade_from_3_to_4 which states that I must be on 3.4.2 or higher before upgrading.

I'd like to rollback PBS using the created pbs3-etc-backup-2025-09-11.tar.gz file from the community script. Looking for some help/direction on how to best do so. Thanks.

[MickLesk]

set -euo pipefail

cat >/etc/apt/preferences.d/00-trixie-block.pin <<'EOF'
Package: *
Pin: release n=trixie
Pin-Priority: -1
EOF

rm -f /etc/apt/sources.list.d/*.list /etc/apt/sources.list.d/*.sources || true
sed -i '/proxmox/d;/trixie/d' /etc/apt/sources.list || true

cat >/etc/apt/sources.list.d/debian.sources <<'EOF'
Types: deb
URIs: http://deb.debian.org/debian
Suites: bookworm
Components: main contrib
Signed-By: /usr/share/keyrings/debian-archive-keyring.gpg

Types: deb
URIs: http://security.debian.org/debian-security
Suites: bookworm-security
Components: main contrib
Signed-By: /usr/share/keyrings/debian-archive-keyring.gpg

Types: deb
URIs: http://deb.debian.org/debian
Suites: bookworm-updates
Components: main contrib
Signed-By: /usr/share/keyrings/debian-archive-keyring.gpg
EOF


cat >/etc/apt/sources.list.d/proxmox-pbs.sources <<'EOF'
Types: deb
URIs: http://download.proxmox.com/debian/pbs
Suites: bookworm
Components: pbs-no-subscription
Signed-By: /usr/share/keyrings/proxmox-archive-keyring.gpg
EOF

apt-get update -qq
apt-cache policy proxmox-backup-server proxmox-backup proxmox-backup-client | sed 's/^/  /'

[di5cord20]

thanks @MickLesk . After running your provided response, i get the following on apt update:

Hit:1 http://download.proxmox.com/debian/pbs bookworm InRelease
Hit:2 http://deb.debian.org/debian bookworm InRelease
Hit:3 http://deb.debian.org/debian bookworm-updates InRelease
Hit:4 http://security.debian.org/debian-security bookworm-security InRelease
Err:1 http://download.proxmox.com/debian/pbs bookworm InRelease
  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY

I'm going to start a fresh install of PBS 4 at this point as that may be easier than troubleshooting (at least for me).

[di5cord20]

Update: I decided to try rebooting and that seems to have cleared things up. Currently running apt update && apt dist-upgrade. Wanted to share now in case it helps others.