Proxmox VE 9 & Debian 13 Air-Gapped Update Guide

This guide describes how to set up an intermediate APT cache on an internet-connected machine (via VirtualBox) and transfer that cache to an air-gapped environment to update Proxmox VE 9 installations. 
 Phase 1: VirtualBox Setup (Internet-Facing Host) 
 On your internet-connected machine, you need two virtual entities: the Cache Server and a Template Proxmox VM to "pull" the initial data. 
 1.1 Debian 13 (Trixie) Cache VM 
 
 Create VM: 2 vCPUs, 2GB RAM, 50GB+ Disk (depending on how many packages you cache). 
 Networking: Use Bridged Adapter to ensure it has its own IP on your local network. 
 OS Installation: Install a minimal Debian 13 (Netinst). Ensure SSH server and Standard system utilities are selected. 
 
 I did set it up with the hostname prox-cache in my lan with the domain lan.zn80.net with the IP 192.168.0.240/24 . 
 When you get asked what to install in addition to the basis system, deselct the Desktop Environment and select only WebServer , SSH Server and Standard System Utilities . 
 After starting the system, enable the sshd.service 
 systemctl enable sshd.service
systemctl start sshd.service
 
 Also add a static IP address by editing the /etc/network/interfaces file: 
 # The primary network interface
allow-hotplug enp0s3
iface enp0s3 inet static
 address 192.168.0.240/24
 gateway 192.168.0.1

 
 This should be it for now. Continue with installing the Proxmox-Feeder. 
 1.2 Proxmox VE 9 "Feeder" VM 
 To populate the cache, you need a machine that requests the specific Proxmox 9 packages. 
 
 Create VM: 2 vCPUs, 4GB RAM, 20GB Disk. 
 OS Installation: Install Proxmox VE 9 (or Debian 13 + PVE 9 packages). 
 Networking: Ensure it can reach the Debian 13 Cache VM. 
 
 Id did set it up with the hostname prox-feeder in my lan with the domain lan.zn80.net with the IP 192.168.0.241/24 . 
 After installing the proxmox feeder vm we need to configure the in the next steps. Do not update the initial installation yet. 
 
 Phase 2: Setting up APT-Cacher-NG (Cache Server) 
 Before installing the cache, we will optimize the Debian mirror selection to ensure the fastest download speeds. 
 2.1 Optimization: Selecting the Fastest Mirror 
 Install netselect-apt to automatically determine the best mirror for Debian 13. 
 # Install netselect-apt
sudo apt update
sudo apt install netselect-apt -y

# Find the fastest mirror for Debian 13 (Trixie)
# This creates a 'sources.list' file in the current directory
sudo netselect-apt trixie

# Backup existing sources and apply the new optimized list
sudo mv /etc/apt/sources.list /etc/apt/sources.list.bak
sudo mv sources.list /etc/apt/sources.list
sudo apt update
 
 2.2 Install and Configure APT-Cacher-NG 
 Now, install the caching service which will use the fast mirrors selected above. 
 Installation 
 sudo apt install apt-cacher-ng -y
 
 Configuration 
 Edit the configuration to ensure it allows Proxmox repositories: 
 sudo nano /etc/apt-cacher-ng/acng.conf
 
 Ensure the following line is active to allow HTTPS tunneling if necessary:
 PassThroughPattern: .* 
 Restart Service 
 sudo systemctl restart apt-cacher-ng
 
 
 Phase 3: Populating the Cache 
 On your Proxmox VE 9 "Feeder" VM , tell APT to use the Cache Server. 
 
 Create a proxy configuration file: 
 
 echo 'Acquire::http::Proxy "http://<IP-OF-CACHE-SERVER>:3142";' | sudo tee /etc/apt/apt.conf.d/00proxy
 
 
 Run the updates to pull data into the cache: 
 
 apt update
apt dist-upgrade -y
```
Now, all downloaded `.deb` files are stored on the Debian 13 Cache VM in `/var/cache/apt-cacher-ng`.
 
 
 Phase 4: Exporting the Cache to the Air-Gapped System 
 Since the target system is air-gapped, we must physically move the data. 
 4.1 On the Internet-Connected Cache VM: 
 Compress the cache data: 
 sudo tar -cvzf pve-cache-export.tar.gz /var/cache/apt-cacher-ng
 
 Copy pve-cache-export.tar.gz to a USB drive or mobile storage. 
 4.2 On the Air-Gapped Target System: 
 You need a machine (or LXC container) in the air-gapped network to act as the Local Cache Server . 
 
 Install a Debian 13 LXC or VM on your air-gapped Proxmox. 
 Install apt-cacher-ng (you might need to install this manually via .deb files once if the container isn't prepared). 
 Import the data: 
 
 # Extract the data to the correct location
sudo tar -xvzf /path/to/usb/pve-cache-export.tar.gz -C /
sudo chown -R apt-cacher-ng:apt-cacher-ng /var/cache/apt-cacher-ng
sudo systemctl restart apt-cacher-ng
 
 
 Phase 5: Configuring Air-Gapped Proxmox Clients 
 Now, configure all your air-gapped Proxmox 9 nodes to use the internal cache server. 
 5.1 Set the Proxy 
 Edit /etc/apt/apt.conf.d/00proxy on every node: 
 ```text
Acquire::http::Proxy "http://<INTERNAL-CACHE-LXC-IP>:3142";
```
 
 5.2 Update Repository Sources 
 Ensure your /etc/apt/sources.list and /etc/apt/sources.list.d/pve-enterprise.list point to standard URLs. Even though there is no internet, apt-cacher-ng will trick APT into thinking it's talking to the real servers, while actually serving the files from the local disk. 
 Example for Proxmox 9 (No-Subscription): 
 deb [http://download.proxmox.com/debian/pve](http://download.proxmox.com/debian/pve) trixie pve-no-subscription
 
 5.3 Run Update 
 apt update
apt dist-upgrade
 
 
 Troubleshooting & Maintenance 
 
 Maintenance: To update the air-gapped system again, repeat Phase 3 (on the internet host) and Phase 4 (transfer). 
 Disk Space: Monitor /var/cache/apt-cacher-ng . You can use the web interface at http://<cache-ip>:3142/acng-report.html to manage the expiration of old packages. 
 
 
 Soll ich dir noch spezifische Konfigurationsparameter für die Proxmox Enterprise Repositories heraussuchen, falls du diese über den Cache spiegeln möchtest?