{
  "slug": "filesystem-uuid",
  "term": "Filesystem UUID",
  "aliases": [
    "file system UUID",
    "filesystem universally unique identifier"
  ],
  "definition": "A filesystem UUID is an identifier stored in filesystem metadata and used to select that filesystem independently of its device pathname.",
  "note": "Ext4 stores its 128-bit s_uuid at byte offset 0x68 within the superblock; this is distinct from a containing partition's identifier. [ext4-super]\n\nLinux mount's UUID= and PARTUUID= selectors refer to different layers. Reformatting a filesystem does not itself change the partition identifier. Copied filesystems can retain the same UUID. [mount-identifiers]\n\nA filesystem UUID is an identifier, not a content digest. Matching UUIDs do not establish that two recovery artifacts are distinct or unchanged.",
  "status": "shipping",
  "advantages": [],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "updated": "2026-11-03",
  "limitations": [
    "UUID availability and representation depend on the filesystem format.",
    "A recognized identifier does not establish filesystem health or recovery completeness."
  ],
  "related": [
    "unique-partition-guid",
    "partition-type-guid",
    "ext4"
  ],
  "citations": [
    {
      "id": "ext4-super",
      "title": "Linux v6.12 ext4 superblock: s_uuid field",
      "url": "https://raw.githubusercontent.com/torvalds/linux/v6.12/Documentation/filesystems/ext4/super.rst",
      "accessed": "2026-11-03"
    },
    {
      "id": "mount-identifiers",
      "title": "util-linux v2.41 mount(8): filesystem and partition selectors",
      "url": "https://raw.githubusercontent.com/util-linux/util-linux/v2.41/sys-utils/mount.8.adoc",
      "accessed": "2026-11-03"
    }
  ],
  "provenance": [
    "Source review of Linux v6.12 ext4 documentation and util-linux v2.41 mount semantics; no filesystem-formatting or recovery experiment."
  ]
}