apache/hadoop · error · SnapshotAccessControlException

Modification on a read-only snapshot is disallowed

Error message

Modification on a read-only snapshot is disallowed

What it means

Error "Modification on a read-only snapshot is disallowed" thrown in apache/hadoop.

Source

Thrown at hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSDirectory.java:1941

  void checkTraverse(FSPermissionChecker pc, INodesInPath iip,
      DirOp dirOp) throws AccessControlException, UnresolvedPathException,
          ParentNotDirectoryException {
    final boolean resolveLink;
    switch (dirOp) {
      case READ_LINK:
      case WRITE_LINK:
      case CREATE_LINK:
        resolveLink = false;
        break;
      default:
        resolveLink = true;
        break;
    }
    checkTraverse(pc, iip, resolveLink);
    boolean allowSnapshot = (dirOp == DirOp.READ || dirOp == DirOp.READ_LINK);
    if (!allowSnapshot && iip.isSnapshot()) {
      throw new SnapshotAccessControlException(
          "Modification on a read-only snapshot is disallowed");
    }
  }

  /**
   * Check whether current user have permissions to access the path. For more
   * details of the parameters, see
   * {@link FSPermissionChecker#checkPermission}.
   */
  void checkPermission(FSPermissionChecker pc, INodesInPath iip,
      boolean doCheckOwner, FsAction ancestorAccess, FsAction parentAccess,
      FsAction access, FsAction subAccess)
    throws AccessControlException {
    checkPermission(pc, iip, doCheckOwner, ancestorAccess,
        parentAccess, access, subAccess, false);
  }

  /**

View on GitHub (pinned to 2add963021)

Solutions

1. Snapshots are read-only; perform the modification on the original directory instead of the snapshot path.
2. Restore/copy the snapshot content to a writable location before modifying.

When it happens

Trigger: Attempting a metadata mutation on a path inside a read-only snapshot.

Common situations: See trigger scenarios.

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/a9507ad9ba54aada. Report an issue: GitHub.