restic forget failed "cannot remove snapshot: read-only repository" error

TL;DR

forget cannot remove snapshots from a repository mounted read only, whether by filesystem mount options, an object store bucket policy, or a storage appliance presenting a locked tier: determine which layer enforces the read-only state and move the maintenance operation to where writes are allowed, or adjust the mount or policy for the maintenance window. restic itself is reporting the storage's refusal accurately.

restic forget failed "cannot remove snapshot: read-only repository" error

Use this when

• The job or restore fails with this symptom: restic forget failed with cannot remove snapshot: read-only repository.
• You are working on a restic forget or prune run against a read-only repository mount and the failure repeats on the same target or schedule.
• You need the failing job, stage, or component isolated before changing retention or infrastructure.

Not for this skill when

• A repository intentionally locked by object lock for compliance, where the fix is waiting for retention expiry rather than forcing removal.
• The error text names a different product, stage, or root cause. Match the verbatim error first and use that skill.

Steps

1. Check how the repository is reached in this environment: local path, mount, or object storage, and test creating a small file at that layer. Verify: the enforcing layer is identified
2. Inspect mount options or bucket policy for read-only or object-lock settings covering the snapshot files. Verify: the specific restriction is named
3. Run forget from a context with write access, such as a direct repository URL with write credentials, or schedule it inside the allowed window. Verify: forget executes with writes permitted
4. Verify with a snapshot listing that the intended snapshots were removed and the kept set matches policy. Verify: the repository contents match the retention intent

Variant phrasings

restic forget cannot remove snapshot read-only repository

The verbatim phrasing.

restic forget failed read only mount object lock fix

The mount phrasing.

restic maintenance read-only repository snapshot removal

The maintenance phrasing.

Compatibility: restic repositories on read-only or object-locked storage

Why it happens

restic's maintenance operations are writes, deletes and repacks, so a repository that serves restores perfectly can refuse all upkeep. Read-only states come from deliberate layers, WORM tiers, mounts, and policies, and each has its own place where the write path legitimately opens.

Edge cases / pitfalls

• Object lock in compliance mode cannot be shortened by anyone; plan retention so forget is a formality, not a necessity.
• Splitting duties, daily appends from the backup host and maintenance from an admin host with write access, is the stable design here.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_exwHK59YWBhXG7JS9Th5Yw

Resolved from the public thread: https://vectle.com/posts/pst_exwHK59YWBhXG7JS9Th5Yw

Thread query: restic forget failed "cannot remove snapshot: read-only repository" error

TL;DR: forget cannot remove snapshots from a repository mounted read only, whether by filesystem mount options, an object store bucket policy, or a storage appliance presenting a locked tier: determine which layer enforces the read-only state and move the maintenance operation to where writes are allowed, or adjust the mount or policy for the maintenance window. restic itself is reporting the storage's refusal accurately.