containerd/containerd · error

failed to write diff: %w

Error message

failed to write diff: %w

What it means

For uncompressed diffs (compressionType == Uncompressed), Compare writes the diff directly to the content writer via archive.WriteDiff(ctx, cw, lowerRoot, upperRoot, ...). Failure of that write is wrapped as "failed to write diff". It indicates the tar walk of the mounts or the write into the content store failed.

Source

Thrown at plugins/diff/walking/differ.go:163

				} else {
					compressed, errOpen = compression.CompressStream(cw, compressionType)
					if errOpen != nil {
						return fmt.Errorf("failed to get compressed stream: %w", errOpen)
					}
				}
				errOpen = archive.WriteDiff(ctx, io.MultiWriter(compressed, dgstr.Hash()), lowerRoot, upperRoot, writeDiffOpts...)
				compressed.Close()
				if errOpen != nil {
					return fmt.Errorf("failed to write compressed diff: %w", errOpen)
				}

				if config.Labels == nil {
					config.Labels = map[string]string{}
				}
				config.Labels[labels.LabelUncompressed] = dgstr.Digest().String()
			} else {
				if errOpen = archive.WriteDiff(ctx, cw, lowerRoot, upperRoot, writeDiffOpts...); errOpen != nil {
					return fmt.Errorf("failed to write diff: %w", errOpen)
				}
			}

			var commitopts []content.Opt
			if config.Labels != nil {
				commitopts = append(commitopts, content.WithLabels(config.Labels))
			}

			dgst := cw.Digest()
			if errOpen = cw.Commit(ctx, 0, dgst, commitopts...); errOpen != nil {
				if !errdefs.IsAlreadyExists(errOpen) {
					return fmt.Errorf("failed to commit: %w", errOpen)
				}
				errOpen = nil
			}

			info, err := s.store.Info(ctx, dgst)
			if err != nil {

View on GitHub (pinned to 4246446a2b)

Solutions

1. Read the wrapped error: EACCES/EPERM while walking indicates fix permissions on snapshot files or run with adequate privileges.
2. Check content store disk space and backend health (ENOSPC surfaces here).
3. Exclude volatile/changing paths from the diff (writeDiffOpts) or re-mount a consistent snapshot before Compare.
4. Retry the operation after transient I/O conditions clear.

// Ensure mount roots exist and are readable before Compare:
for _, m := range append(lower, upper...) {
    if _, err := os.Stat(m.Target); err != nil { return err }
}

if err := differ.Compare(ctx, lower, upper, opts...); err != nil {
    var perr *os.PathError
    if errors.As(err, &perr) {
        // permission/path problem walking the snapshot: fix ACLs or rerun as admin
    }
    return err
}

When it happens

Trigger: archive.WriteDiff into the raw content writer returns an error during an uncompressed Compare - file read errors while walking, content writer I/O failure, disk full, or deleted/changed files mid-walk.

Common situations: Unreadable/special files inside the snapshot (permission denied while walking), content store disk exhaustion, or files mutated under the temp mount during diffing.

Related errors

• failed to write bootstrap.json for bundle %s: %w
• failed to create container io: %w
• failed to write compressed diff: %w
• unable to discard to offset
• no processor for media-type

AI-assisted analysis of containerd/containerd@4246446a2b (2026-09-02). Data as JSON: /api/errors/c7bc7778d7f27ec0. Report an issue: GitHub.