{
  "slug": "fsync",
  "term": "fsync",
  "aliases": [
    "fsync()"
  ],
  "definition": "fsync is a file-synchronization operation that requests persistence of a file's modified data and associated metadata before reporting completion.",
  "note": "On Linux, syncing the file does not necessarily persist its containing directory entry; the directory needs its own sync. fdatasync may omit metadata unnecessary for retrieving the data. A failed sync must be treated as an unresolved durability event, not silently replaced by a later successful return.",
  "status": "shipping",
  "advantages": [],
  "limitations": [],
  "related": [
    "crash-consistency",
    "writeback-error",
    "write-back-cache"
  ],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "citations": [
    {
      "id": "linux-fsync",
      "title": "Linux man-pages 6.19: fsync(2)",
      "url": "https://man7.org/linux/man-pages/man2/fsync.2.html",
      "accessed": "2026-10-10"
    },
    {
      "id": "hesela-fsync",
      "title": "Hesela: Why retrying a failed fsync does not prove durability",
      "url": "https://hesela.com/analyses/fsync-failure-retry-durability/",
      "accessed": "2026-10-10"
    }
  ],
  "updated": "2026-10-10"
}