Post

Backup & Restore Proxmox OS boot/root disk

Posted Updated
By Filip Zverec 6 min read

Introduction

Recently I’ve received an email notification about one of my drives failing in my proxmox cluster. It turned out to be my proxmox boot drive, which is the only one not in the ZFS pool (but it just ext4). I’ve started to look through the official documentation, guides to look for what’s the best way to replace this drive and I’ve decided to share my 2-cents on in and how I did it in the end.

Disk replacement options

It turns out there isn’t really a native/easy way about this.

You could

  • backup all VMs/LXc to PBS (aka proxmox backup storage), fresh install the proxmox one new disk and restore the VMs/LXc through PBS
  • backup these folders somewhere external ( /etc/corosync/* /etc/pve /etc/passwd /etc/network/interfaces /etc/resolv.conf /etc/hostname /etc/hosts /var/lib/pve-cluster/config.db) -> do a fresh proxmox install -> replace these folders -> reboot
  • use one of the million tools on the internet to do the step above somewhat more automatically - example
  • clone the disk with (with sfdisk and dd) - guide
  • or if you are well prepared and running root on ZFS, just put the new drive in and resilver the pool - guide

Then I’ve found out about existance of proxmox-backup-client tool

Proxmox backup client

Advantages

  • installed on proxmox by default
  • great integration with PBS (proxmox backup storage)
  • easy to use
  • allow us to create automatic backups of root OS disk to PBS

Disadvantages

  • need to be used with PBS (maybe a deal breaker for someone not taking backups or taking backups differently)

How to backup / restore OS root disk

Take backup

Open shell on proxmox node (can be web GUI)

First we need to export some env variables to make our life using these commands easier (you could also use flag to use them in every command)

You can either use root user or dedicated user for backups. As an example I’ll show you the root user

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export PBS_REPOSITORY=user@realm@<IP>:datastore
export PBS_PASSWORD="password"
export PBS_FINGERPRINT=""fingerprint"

Replace the user, realm, IP, datastore, password and fingerprint for your values. You can find them for example in the PBS GUI-> Datastore -> YourDatastore-> Sumarry -> Show connection information

pbs_string

Except for the password. That you have to remember, it’s the same password you used for GUI login.

Example

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export PBS_REPOSITORY=root@pam@10.1.1.19:backups
export PBS_PASSWORD=Password332!
export PBS_FINGERPRINT="9a:a7:19:XX:58:fb:c3:5d:XX:56:f6:4f:45:3a:XX:21:90:b8:f1:aa:e6:7c:45:12:42:e7:69:c2:17:28:a4:71"

Take backup of disk

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proxmox-backup-client backup root.img:/dev/sdx --backup-id "gandalf"
  • root.img - name of the image showing in PBS (can be anything really)
  • :/ - path of what to take backup of. In our case everything root related under /
  • dev/sdx - name of the disk where the proxmox OS is stored. You can find this information in proxmox GUI -> node -> disks -> look for partitions (BIOS boot, EFI, LVM). Check out the image bellow for more guidance
  • -backup-id - will be used as hostname showing in PBS (can be anything really)

proxmox_disk_name

NOTE: This will take from few minutes to few hours depending on size of your boot disk (hopefully small), disk speeds, proxmox CPUs etc…

It it’s going correctly it should look like this

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root@gandalf:~# proxmox-backup-client backup root.img:/dev/sdd --backup-id "gandalf"
Starting backup: host/gandalf/2025-06-07T10:53:31Z    
Client name: gandalf    
Starting backup protocol: Sat Jun  7 12:53:31 2025    
storing login ticket failed: $XDG_RUNTIME_DIR must be set
No previous manifest available.    
Upload image '/dev/sdd' to 'root@pam@10.1.1.19:8007:backups' as root.img.fidx    
processed 9.672 GiB in 1m, uploaded 8.512 GiB
processed 22.895 GiB in 2m, uploaded 12.953 GiB
processed 38.668 GiB in 3m, uploaded 17.609 GiB
processed 56.313 GiB in 4m, uploaded 20.563 GiB
processed 69.734 GiB in 5m, uploaded 26.637 GiB
processed 88.809 GiB in 6m, uploaded 26.824 GiB
processed 108.688 GiB in 7m, uploaded 26.844 GiB
processed 128.289 GiB in 8m, uploaded 27.211 GiB
processed 148.172 GiB in 9m, uploaded 27.219 GiB
processed 168.063 GiB in 10m, uploaded 27.227 GiB
processed 184.984 GiB in 11m, uploaded 29.203 GiB
processed 204.844 GiB in 12m, uploaded 29.211 GiB
processed 224.473 GiB in 13m, uploaded 29.23 GiB
root.img: had to backup 29.284 GiB of 238.475 GiB (compressed 6.869 GiB) in 822.61 s (average 36.453 MiB/s)
root.img: backup was done incrementally, reused 209.191 GiB (87.7%)
Duration: 822.64s    
End Time: Sat Jun  7 13:07:14 2025

Checkout the backup

Either by CLI

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proxmox-backup-client snapshot list

Or in the PBS GUI under the Datastore content pbs_backup

[A] Connect new disk to proxmox

Connect the new disk to your server, and checkout it’s name either by CLI

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lsblk

In the the proxmox GUI, again under disks as last time (don’t forget to click reload button)

[B] Create fresh install on the current disk

As an alternative you could also create new fresh proxmox install if you are just reinstalling OS. But this guide will focus on the A option

Restore / clone root to a new disk

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proxmox-backup-client restore host/gandalf/2025-06-07T10:53:31Z root.img - | sudo dd of=/dev/sdx status=progress bs=1M
  • host/gandalf/2025-06-07T10:53:31Z - name of the backup which we have listed in previous step
  • root.img - name of the image showing in PBS (can be anything really)
  • /dev/sdx - name of the disk WHERE WE WANT TO RESTORE/CLONE the image (new disk)

Warning Be careful not to rewrite any other disk.

Disconnect the old failing disk

In the BIOS swap new ssd as boot one

Bonus

Automate root disk backups backups

Let’s automate this process, so we have relatively up to date root OS if we would want to restore it. And while we are at it, let’s create cleanup policies, so it won’t get cluttered in the PBS

In the PBS create new namespace under datastore

pbs_create_ns

Create prune job for new namespace

pbs_prune_job

Change the values to your preferences. I’ve setup mine to only keep last backup, and run this job weekly at sunday.

Create backup service on the proxmox node

In the proxmox shell type

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vim /etc/systemd/system/rootbackup.service

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[Unit]
Description=Backup root to PBS
After=network-online.target

[Service]
#same ENVs we used in previous step
Environment=PBS_FINGERPRINT=fingerprint
Environment=PBS_PASSWORD=api_key/password
Environment=PBS_REPOSITORY=user@realm@<IP>:datastore
Type=oneshot
#change the disk name (/dev/sdx) and backup-id (gandalf) and ns (rootbackup) to your values
# ns = namespace
ExecStart=proxmox-backup-client backup root.img:/dev/sdx --backup-id "gandalf" --ns "rootbackup"

[Install]
WantedBy=default.target

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vim /etc/systemd/system/rootbackup.timer

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[Unit]
Description=Backup System Daily
RefuseManualStart=no
RefuseManualStop=no

[Timer]
# run once a month at 3 AM on the 1st
OnCalendar=*-*-1 03:00:00
Unit=rootbackup.service

[Install]
WantedBy=timers.target

Enable the service

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systemctl daemon-reload
systemctl enable --now rootbackup.timer

You can test the first backup with

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systemctl start rootbackup
Homelab
proxmox
This post is licensed under CC BY 4.0 by the author.