{"record":{"id":"1076800dfa30eb48","repo":"containerd/containerd","slug":"failed-to-sync-tar2ext4-vhd-to-disk-w","errorCode":null,"errorMessage":"failed to sync tar2ext4 vhd to disk: %w","messagePattern":"failed to sync tar2ext4 vhd to disk: %w","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"error","filePath":"plugins/diff/lcow/lcow.go","lineNumber":164,"sourceCode":"\tlayerPath := path.Join(layer, \"layer.vhd\")\n\toutFile, err := os.Create(layerPath)\n\tif err != nil {\n\t\treturn emptyDesc, err\n\t}\n\tdefer func() {\n\t\tif err != nil {\n\t\t\toutFile.Close()\n\t\t\tos.Remove(layerPath)\n\t\t}\n\t}()\n\n\terr = tar2ext4.Convert(rc, outFile, tar2ext4.ConvertWhiteout, tar2ext4.AppendVhdFooter, tar2ext4.MaximumDiskSize(maxLcowVhdSizeGB))\n\tif err != nil {\n\t\treturn emptyDesc, fmt.Errorf(\"failed to convert tar2ext4 vhd: %w\", err)\n\t}\n\terr = outFile.Sync()\n\tif err != nil {\n\t\treturn emptyDesc, fmt.Errorf(\"failed to sync tar2ext4 vhd to disk: %w\", err)\n\t}\n\toutFile.Close()\n\n\t// Read any trailing data\n\tif _, err := io.Copy(io.Discard, rc); err != nil {\n\t\treturn emptyDesc, err\n\t}\n\n\terr = security.GrantVmGroupAccess(layerPath)\n\tif err != nil {\n\t\treturn emptyDesc, fmt.Errorf(\"failed GrantVmGroupAccess on layer vhd: %v: %w\", layerPath, err)\n\t}\n\n\treturn ocispec.Descriptor{\n\t\tMediaType: ocispec.MediaTypeImageLayer,\n\t\tSize:      rc.c,\n\t\tDigest:    digester.Digest(),\n\t}, nil","sourceCodeStart":146,"sourceCodeEnd":182,"githubUrl":"https://github.com/containerd/containerd/blob/4246446a2bf7d03837b0244118d858799393bd80/plugins/diff/lcow/lcow.go#L146-L182","documentation":"After a successful tar2ext4 conversion, Apply calls outFile.Sync() to flush the VHD to disk; a Sync failure is wrapped as 'failed to sync tar2ext4 vhd to disk'. This indicates the OS could not flush written data to stable storage, so the produced VHD may not be durable.","triggerScenarios":"outFile.Sync() returning an error after Convert succeeded — typically ENOSPC (disk full), EIO (disk fault), or invalid file state on the Windows/LCOW filesystem.","commonSituations":"Hosts running out of disk space mid-write; failing storage hardware; unusual mounts (e.g. network filesystems with sync issues).","solutions":["Free disk space on the target volume and retry","Check disk health (SMART) and filesystem errors; run fsck/chkdsk if needed","Retry the Apply after resolving storage issues"],"exampleFix":"// before: sync fails, layer lost\n// after: pre-check available space\nif stat, err := outDirStat(); err == nil && stat.Available < requiredBytes {\n    return fmt.Errorf(\"insufficient disk space\")\n}\nerr = outFile.Sync()","handlingStrategy":"retry","validationCode":"if stat, err := fs.Stat(volume); err == nil && stat free space < vhdSize {\n    return fmt.Errorf(\"insufficient space for vhd sync\")\n}","typeGuard":null,"tryCatchPattern":"err := applyLcowLayer(ctx, desc, mounts)\nif err != nil && strings.Contains(err.Error(), \"failed to sync tar2ext4 vhd to disk\") {\n    // check disk space/health, then retry once\n    if freeSpaceOK() {\n        err = applyLcowLayer(ctx, desc, mounts)\n    }\n    return err\n}","preventionTips":["Monitor disk free space and SMART health on hosts running LCOW diffs","Avoid writing VHDs to network/unreliable filesystems","Alert on ENOSPC/EIO kernel logs"],"tags":["lcow","fsync","disk","windows"],"backgroundTag":"disk-sync-failed","analyzedSha":"4246446a2bf7d03837b0244118d858799393bd80","analyzedAt":"2026-09-02T00:14:43.053Z","contentChangedAt":null,"schemaVersion":2},"datasetVersion":"2026-09-09T06:17:21.866Z"}