apache/druid · error · IllegalStateException

Path [%s] is not writable, check permissions

Error message

Path [%s] is not writable, check permissions

What it means

FileUtils.createTempDirInLocation throws this ISE when the JVM cannot create a temporary directory because the OS reported the parent path is not writable. It maps AccessDeniedException or a 'Read-only file system' FileSystemException from the underlying createDirectory call to this clearer message. It indicates a filesystem permission or mount-state problem, not a bug in caller code.

Source

Thrown at processing/src/main/java/org/apache/druid/java/util/common/FileUtils.java:490

  }

  @SuppressForbidden(reason = "Files#createTempDirectory")
  public static File createTempDirInLocation(final Path parentDirectory, @Nullable final String prefix)
  {
    try {
      final Path tmpPath = Files.createTempDirectory(
          parentDirectory,
          prefix == null || prefix.isEmpty() ? "druid" : prefix
      );
      return tmpPath.toFile();
    }
    catch (IOException e) {
      // Some inspection to improve error messages.
      if (e instanceof NoSuchFileException && !parentDirectory.toFile().exists()) {
        throw new ISE("Path [%s] does not exist", parentDirectory);
      } else if ((e instanceof FileSystemException && e.getMessage().contains("Read-only file system"))
                 || (e instanceof AccessDeniedException)) {
        throw new ISE("Path [%s] is not writable, check permissions", parentDirectory);
      } else {
        // Well, maybe it was something else.
        throw new ISE(e, "Failed to create temporary directory in path [%s]", parentDirectory);
      }
    }
  }

  /**
   * Create "directory" and all intermediate directories as needed. If the directory is successfully created, or already
   * exists, returns quietly. Otherwise, throws an IOException.
   *
   * Simpler to use than {@link File#mkdirs()}, and more reliable since it is safe from races where two threads try
   * to create the same directory at the same time.
   *
   * The name is inspired by UNIX {@code mkdir -p}, which has the same behavior.
   */
  @SuppressForbidden(reason = "File#mkdirs")
  public static void mkdirp(final File directory) throws IOException

View on GitHub (pinned to 9b90983fd2)

Solutions

1. Check and fix permissions on the parent directory: chown/chmod so the process user has write access
2. Point the temp-dir configuration at a writable location (e.g. a writable volume or /tmp)
3. If the filesystem was remounted read-only, remount it read-write or fix the underlying disk issue
4. In containers, mount a writable emptyDir/PV for temp directories and avoid readOnlyRootFilesystem without mounts
5. Verify with: sudo -u <druid-user> touch <path>/writetest

Example fix

// before
FileUtils.createTempDir(new File("/opt/druid/tmp")); // /opt is read-only
// after
FileUtils.createTempDir(new File("/var/tmp/druid")); // writable volume

File dir = new File(path);
if (!dir.isDirectory()) throw new IllegalStateException("Not a directory: " + path);
File probe = new File(dir, ".write-probe");
try { if (!probe.createNewFile()) throw new IllegalStateException("Not writable"); }
finally { probe.delete(); }

static boolean isWritableDir(File dir) {
  return dir != null && dir.isDirectory() && dir.canWrite();
}

try {
  File tmp = FileUtils.createTempDir(parent);
} catch (ISE e) {
  if (e.getMessage() != null && e.getMessage().contains("not writable")) {
    // fix permissions or switch to fallback dir
    tmp = FileUtils.createTempDir(new File(System.getProperty("java.io.tmpdir")));
  } else throw e;
}

When it happens

Trigger: Calling FileUtils.createTempDir (which delegates to createTempDirInLocation) with a parent directory the process cannot write to, on a read-only mounted filesystem, or where the directory's permission bits deny write access to the running user.

Common situations: Configuring druid.server.tempDir or intermediate persist dirs on a read-only container filesystem; running Druid as a non-root user without write access to java.io.tmpdir; disk remounted read-only after hardware errors; Kubernetes readOnlyRootFilesystem without an emptyDir mount.

Understand the failure class

Background: Permission denied / not authorized / 403 Forbidden: access-control rejections when the caller lacks the required role, grant, or ownership — this error's family across 18 libraries.

Related errors

• Cannot create tempDir [%s] for google storage connector
• Cannot list directory [%s]
• Could not create temp distribution directory.
• Could not close channel for level [%d] and rank [%d]
• Unable to close channel for name :

AI-assisted analysis of apache/druid@9b90983fd2 (2026-09-07). Data as JSON: /api/errors/6093c5183579163e. Report an issue: GitHub.