After Upgrade to Veeam Backup & Replication 12.1, Backup of Linux VM Fails With: "Failed to check fingerprint"
| KB ID: | 4524 |
| Product: | Veeam Backup & Replication | 12.1 |
| Published: | 2023-12-12 |
| Last Modified: | 2023-12-12 |
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Challenge
After upgrading to Veeam Backup & Replication 12.1, Backup jobs for Linux VMs that operated successfully before the upgrade now fail with:
Unable to connect to guest OS for guess process. Failed to check fingerprint.
Cause
During the upgrade to Veeam Backup & Replication 12.1, the format used to store SSH fingerprints for Linux machines is updated. However, for environments where the configuration database was stored in a Microsoft SQL instance running SQL 2022 or 2019, the conversion process fails to correctly process blank current_fingerprint values in the Backup.Model.HostSshFingerprint table. Those blank values are replaced with NULL, which is unexpected by Veeam Backup & Replication.
Solution
To resolve this issue, manual fingerprint validation must be performed for each machine that failed with the error.
- In the Main Menu (≡), click Options.
- Switch to the Security tab.
- In the section labeled "Linux hosts authentication," change the setting to:
Add unknown hosts to the list manually (more secure) - Rerun the job(s) that failed.
- Validate SSH Fingerprints and Trust entries within the Untrusted node in the Inventory view.
- Run the jobs that failed once more.
- After all jobs have returned to an operational state, you may return the Linux host authentication setting to Add all discovered hosts to the list automatically.
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