apache/hadoop · error · IllegalArgumentException

<snapshotDir> is missing.

Error message

<snapshotDir> is missing.

What it means

CreateSnapshot.processOptions (SnapshotCommands.java:67) throws IllegalArgumentException('<snapshotDir> is missing.') when the command receives zero arguments. 'hdfs dfs -createSnapshot' requires at least the snapshot directory (an HDFS snapshottable directory); the snapshot name is the optional second argument.

Source

Thrown at hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/shell/SnapshotCommands.java:67

   */
  public static class CreateSnapshot extends FsCommand {
    public static final String NAME = CREATE_SNAPSHOT;
    public static final String USAGE = "<snapshotDir> [<snapshotName>]";
    public static final String DESCRIPTION = "Create a snapshot on a directory";

    private String snapshotName = null;

    @Override
    protected void processPath(PathData item) throws IOException {
      if (!item.stat.isDirectory()) {
        throw new PathIsNotDirectoryException(item.toString());
      }
    }
    
    @Override
    protected void processOptions(LinkedList<String> args) throws IOException {
      if (args.size() == 0) {
        throw new IllegalArgumentException("<snapshotDir> is missing.");
      } 
      if (args.size() > 2) {
        throw new IllegalArgumentException("Too many arguments.");
      }
      if (args.size() == 2) {
        snapshotName = args.removeLast();
      }
    }

    @Override
    protected void processArguments(LinkedList<PathData> items)
    throws IOException {
      super.processArguments(items);
      if (numErrors != 0) { // check for error collecting paths
        return;
      }
      assert(items.size() == 1);
      PathData sroot = items.getFirst();

View on GitHub (pinned to 2add963021)

Solutions

1. Supply the snapshot directory: 'hadoop fs -createSnapshot /hdfs/dir' (auto-generates a timestamped name) or 'hadoop fs -createSnapshot /hdfs/dir mysnap'
2. Guard scripts: ': "${SNAPDIR:?SNAPDIR must be set}"' before invoking
3. Ensure the directory is snapshottable ('hdfs dfsadmin -allowSnapshot <dir>') once the argument is supplied

Example fix

# before
hadoop fs -createSnapshot
# createSnapshot: <snapshotDir> is missing.

# after
hadoop fs -createSnapshot /data/important mysnap-2026-08-22

# shell: fail fast on unset vars
: "${SNAPDIR:?SNAPDIR must be set}"
hadoop fs -createSnapshot "$SNAPDIR" "$SNAPNAME"

catch (IllegalArgumentException e) when '<snapshotDir> is missing' -> require and validate the directory argument before re-invoking

When it happens

Trigger: 'hadoop fs -createSnapshot' or 'hdfs dfs -createSnapshot' with no positional arguments (flags would already have failed parsing; this is the empty-args case). Scripts invoking createSnapshot with an unquoted/empty $DIR variable also reduce to zero args.

Common situations: Automation where the directory variable is unset or empty ('hadoop fs -createSnapshot "$SNAPDIR"' with SNAPDIR empty); operators testing the command without arguments; copy-paste from docs that show the optional name and omit the required dir placeholder meaning.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

• Too many arguments.
• Invalid read parameters: buf.length=%d, off=%d, len=%d
• Move destination must be different from source for %s.
• offset: %s is out of range [%s, %s]
• Invalid start or len parameter

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/1e8b3ba4543b7417. Report an issue: GitHub.