---
title: SSH Key IDs Exchange Failed While Building a Cluster
description: "When creating or joining a cluster in RELIANOID, the system exchanges SSH keys between nodes to establish secure communication. If this exchange fails, you may see the following error in the logs: ``` (ERROR) cluster :: SSH Keys Ids exchange…"
url: "https://www.relianoid.com/resources/knowledge-base/troubleshooting/ssh-key-ids-exchange-failed-while-building-a-cluster/"
updated: "2025-09-04"
category: Troubleshooting
---

# SSH Key IDs Exchange Failed While Building a Cluster

When creating or joining a cluster in RELIANOID, the system exchanges SSH keys between nodes to establish secure communication.

If this exchange fails, you may see the following error in the logs:

```
(ERROR) cluster :: SSH Keys Ids exchange failed
(ERROR) webgui :: Enabling cluster: SSH Keys Ids exchange failed
```

## Symptoms

Cluster creation or synchronization fails in the **System > Cluster** section of the web UI.

The **System > Logs > syslog** (`/var/log/syslog`) shows errors similar to:

```
ssh-copy-id: ERROR: @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
ERROR: @    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @
ERROR: @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
ERROR: Host key for 10.x.y.z has changed and you have requested strict checking.
ERROR: Host key verification failed.
(ERROR) cluster :: An error happened copying the Id key to the host 10.x.y.z
(ERROR) cluster :: SSH Keys Ids exchange failed
```

This indicates that the remote host key has changed or the local node has a conflicting entry in its SSH `known_hosts` file.

## Cause

The error occurs because:

- The remote cluster node was reinstalled, redeployed, or its SSH host key was regenerated.
- The local node still has the old host fingerprint stored in `/root/.ssh/known_hosts`.
- As a security precaution, SSH refuses to connect since the stored key does not match the new one.

## Resolution

### Remove the old SSH host key entry

On the node reporting the error, run:

```
ssh-keygen -f "/root/.ssh/known_hosts" -R "10.x.y.x"
```

Replace **10.x.y.x** with the IP address of the remote node. Apply this command in both cluster nodes including the remote node IP address.

This will remove outdated fingerprints from `known_hosts`.

### Verify the cleanup

The command should report that entries were found and removed. Example:

```
# Host 10.x.y.x found: line 1
# Host 10.x.y.x found: line 2
# Host 10.x.y.x found: line 3
/root/.ssh/known_hosts updated.
Original contents retained as /root/.ssh/known_hosts.old
```

### Remove the RSA keys in every node

From every node, please remove the RSA keys to be regenerated.

```
rm -f /root/.ssh/id_rsa*
```

### Review **hosts.deny** file

Check that there isn't any host blocked in the `/etc/hosts.deny` file. The command below should show an empty output.

```
grep -v "^#" /etc/hosts.deny
```

In case that the response is not empty, then edit the file `/etc/hosts.deny` and remove the IP address related to the remote host.

### Rebuild the Cluster Service

Go to the Web UI section **System > Cluster**

Rebuild or re-enable the cluster configuration.

The SSH key exchange will be attempted again and should succeed now.

## Additional Notes

If you continue to experience issues, ensure that:

- The nodes can reach each other via SSH (`ssh root@<REMOTE IP>`).
- System clocks are synchronized (use NTP).
- No firewall rules block port 22/TCP between nodes.

After completing these steps, the cluster should build successfully without the SSH Keys Ids exchange failed error.

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