proxmox/docs/node-restore.md

Proxmox Node Restore

Restores a Proxmox node exactly as it previously existed, allowing it to rejoin the cluster without using pvecm delnode.
It works by reconstructing the node’s identity vectors so Corosync and pmxcfs accept it as the same entity.

This method is not guaranteed and depends on perfect identity matching.
If any identity vector differs (hostname, node ID, ring IP, certificates), the node may:

• fail to mount pmxcfs
• fail to join Corosync
• appear as a ghost node
• destabilize the cluster

Use this approach only when you fully understand the identity requirements and the cluster is otherwise healthy.

• 1. Hostname Identity
• 2. Local Name Resolution
• 3. System Users and Groups
• 4. Network Topology
• 5. VFIO Bindings (If Using Passthrough)
• 6. Kernel Flags and Module Loading (If Restoring GRUB)
• 7. Disk Configuration
• 8. SSH Identity
• 9. Corosync Identity
  • single node custer
  • Multi node cluster
• 10. Node‑Specific Artifacts
• 11. Finalize

1. Hostname Identity

Preserve the node’s cluster identity.

• Restore /etc/hostname

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2. Local Name Resolution

Ensure the node can resolve itself and its peers.

• Restore /etc/hosts

3. System Users and Groups

Restore OS‑level identity and UID/GID mapping.

• Restore /etc/passwd
• Restore /etc/group

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4. Network Topology

Restore bridges, VLANs, MTU, and IP assignments.

• Restore /etc/network/interfaces
• Restore /etc/network/interfaces.d/

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5. VFIO Bindings (If Using Passthrough)

Restore PCI passthrough behavior.

• Restore /etc/modprobe.d/

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6. Kernel Flags and Module Loading (If Restoring GRUB)

Restore passthrough‑related kernel parameters.

• Restore /etc/default/grub
• Restore /etc/modules
• Restore /etc/modules.d/

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7. Disk Configuration

Restore storage layout and ZFS pools.

• Restore /etc/fstab
• Import ZFS pools (example: zfs import fastcore)

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8. SSH Identity

Restore admin access and host identity.

• Restore /root/.ssh/*
• Restore /etc/ssh/*

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9. Corosync Identity

single node custer

In some cases, a single Proxmox node can be resurrected simply by restoring the entire /etc/pve directory from backup. This works because /etc/pve (pmxcfs) contains:

• Corosync identity (node ID, ring IPs, cluster membership)
• Cluster certificates
• Node‑specific configuration
• Storage definitions
• VM/CT configuration metadata

If the restored node has the same hostname, same IPs, same Corosync ring addresses, and the cluster still contains the old node entry, then copying the full /etc/pve state can allow the node to rejoin the cluster as if nothing happened.

Multi node cluster

Reconstruct the node’s cluster identity (Rejoin Without Delnode).

• Restore /etc/pve/corosync.conf
• Restore /etc/pve/corosync.pub
• Restore /etc/corosync/authkey

These define:

• cluster topology
• node ID
• ring IPs
• shared authentication

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10. Node‑Specific Artifacts

Restore semantic overlays and local scripts.

• Restore /home/
• Restore /root/
• Restore /opt/

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11. Finalize

If GRUB was restored:

• Run update-grub

Then:

• Reboot

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