Install Proxmox Backup Server on a lowend server

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I recently acquired a storage VPS with just 512MB RAM and a weak CPU scoring around 300 points on Geekbench5, but extremely cheap storage (to the tune of $15/year/TB). I wanted to install Proxmox Backup Server on this, to easily store offsite backups for my Proxmox hypervisors.

However, the Proxmox Backup Server systrem requirements are quite steep. According to the documentation, it requires a relatively fast CPU and at least 4GB RAM. Should I just leave my server idling because it doesn’t meet the system requirements?

Of course not! In the spirit of low-end hosting, I decided to find a way around it.

Installing Proxmox Backup Server

If you are extremely cheap like me, you won’t pick a VPS that even meets the system requirements for the PBS installer! (that is, any box with less than 1GB of RAM)

Therefore, we will have to install Proxmox Backup Server on top of Debian, because the Debian installer is capable of actually finishing on systems with very low RAM. Installing Debian is outside of the scope of this tutorial.

Once Debian is installed, follow Proxmox’s guide for installing PBS on top of Debian. Here is an abbreviated summary:

  1. Add the no-subscription repository to your APT sources.list:
    deb http://download.proxmox.com/debian/pbs buster pbs-no-subscription
  2. Then fetch Proxmox’s GPG key (note that you should also, as a best practice, verify the checksum of the key following the guide linked above):
    wget http://download.proxmox.com/debian/proxmox-ve-release-6.x.gpg -O /etc/apt/trusted.gpg.d/proxmox-ve-release-6.x.gpg
  3. Run apt update and apt install proxmox-backup. (The proxmox-backup package installs everything the PBS installer ISO would, including the PBS kernel, while proxmox-backup-server package installs a more barebones version of PBS.)

Reboot the server. Open your browser and visit your-server-ip:8007, where you should be greeted by the Proxmox Backup Server UI. You can log in using the root user and your root password.

Configuring Proxmox Backup Server

This was the hard part for me, as there is relatively little documentation on how to actually configure PBS when you only have one disk.

The procedure I followed was to just create a datastore on my VPS’s only disk – no need to deal with initializing new disks/directories/ZFS (shudder)/etc.

In the PBS admin interface, go to Datastore > Add Datastore. The name does not matter, but make sure to configure the backing path correctly, as the path is where all of the backup files will go. I chose /backup for my backing path. Configure the prune options (backup retention) if needed.

Once this is configured, you can add the PBS server as a Storage on your Proxmox VE hypervisors. It will function the same as any other storage on Proxmox VE in regards to using it as a backup destination. You can therefore schedule backups and create backups using the tools built into Proxmox VE. Convenient!

(Note that the fingerprint requested by PVE can be found at Dashboard -> Fingerprint in the PBS admin.)

Results

Even though my VPS is far from meeting the PBS system requirements, it still performs quite well. Backing up a small VM from my Proxmox VE hypervisor in New York to my PBS box in Norway, I am able to hit around 320mbit/s sustained, with 100% CPU usage and around 50% RAM usage on the PBS box. The obvious bottleneck here is the CPU, so I’m sure with a better CPU you will be able to achieve better results.

Clearly, if you are willing to go through a little bit of extra hassle, PBS can certainly be used on a very lowend VPS 🙂

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