# 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](#1-hostname-identity)
- [2. Local Name Resolution](#2-local-name-resolution)
- [3. System Users and Groups](#3-system-users-and-groups)
- [4. Network Topology](#4-network-topology)
- [5. VFIO Bindings (If Using Passthrough)](#5-vfio-bindings-if-using-passthrough)
- [6. Kernel Flags and Module Loading (If Restoring GRUB)](#6-kernel-flags-and-module-loading-if-restoring-grub)
- [7. Disk Configuration](#7-disk-configuration)
- [8. SSH Identity](#8-ssh-identity)
- [9. Corosync Identity](#9-corosync-identity)
  - [single node custer](#single-node-custer)
  - [Multi node cluster](#multi-node-cluster)
- [10. Node‑Specific Artifacts](#10-nodespecific-artifacts)
- [11. Finalize](#11-finalize)

## 1. Hostname Identity

Preserve the node’s cluster identity.

- Restore `/etc/hostname`

---

## 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`

---

## 4. Network Topology

Restore bridges, VLANs, MTU, and IP assignments.

- Restore `/etc/network/interfaces`
- Restore `/etc/network/interfaces.d/`

---

## 5. VFIO Bindings (If Using Passthrough)

Restore PCI passthrough behavior.

- Restore `/etc/modprobe.d/`

---

## 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/`

---

## 7. Disk Configuration

Restore storage layout and ZFS pools.

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

---

## 8. SSH Identity

Restore admin access and host identity.

- Restore `/root/.ssh/*`
- Restore `/etc/ssh/*`

---

## 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  

---

## 10. Node‑Specific Artifacts

Restore semantic overlays and local scripts.

- Restore `/home/`
- Restore `/root/`
- Restore `/opt/`

---

## 11. Finalize

If GRUB was restored:

- Run `update-grub`

Then:

- Reboot

---