apache/hadoop · error · IllegalArgumentException

Unknown credential format:

Error message

Unknown credential format: 

What it means

Error "Unknown credential format: " thrown in apache/hadoop.

Source

Thrown at hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/Credentials.java:82

  public enum SerializedFormat {
    WRITABLE((byte) 0x00),
    PROTOBUF((byte) 0x01);

    // Caching to avoid reconstructing the array each time.
    private static final SerializedFormat[] FORMATS = values();

    final byte value;

    SerializedFormat(byte val) {
      this.value = val;
    }

    public static SerializedFormat valueOf(int val) {
      try {
        return FORMATS[val];
      } catch (ArrayIndexOutOfBoundsException e) {
        throw new IllegalArgumentException("Unknown credential format: " + val);
      }
    }
  }

  private static final Logger LOG = LoggerFactory.getLogger(Credentials.class);

  private  Map<Text, byte[]> secretKeysMap = new HashMap<Text, byte[]>();
  private  Map<Text, Token<? extends TokenIdentifier>> tokenMap =
      new HashMap<Text, Token<? extends TokenIdentifier>>();

  /**
   * Create an empty credentials instance.
   */
  public Credentials() {
  }

  /**
   * Create a copy of the given credentials.

View on GitHub (pinned to 2add963021)

Solutions

1. Read the Credentials file with a matching Hadoop version; the stored credential format is not recognized by this reader.
2. Regenerate the token/credentials storage using the current Hadoop version.
3. Check for file corruption in the credentials storage and restore from a known-good copy.

When it happens

Trigger: Thrown at hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/Credentials.java:82 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/e96ec8413850becf. Report an issue: GitHub.