skylot/jadx · critical · JadxRuntimeException

Failed to create temp root directory

Error message

Failed to create temp root directory

What it means

Thrown from the static initializer (line 55: tempRootDir = createTempRootDir()) when Files.createTempDirectory(JADX_TMP_INSTANCE_PREFIX) fails. Because this runs at class-load time, the failure manifests as an ExceptionInInitializerError wrapping this JadxRuntimeException. It means the OS default temp directory (java.io.tmpdir, typically /tmp) is not writable or cannot allocate a new directory.

Source

Thrown at jadx-core/src/main/java/jadx/core/utils/files/FileUtils.java:79

	public static synchronized Path updateTempRootDir(Path newTempRootDir) {
		try {
			makeDirs(newTempRootDir);
			Path dir = Files.createTempDirectory(newTempRootDir, JADX_TMP_INSTANCE_PREFIX);
			tempRootDir = dir;
			dir.toFile().deleteOnExit();
			return dir;
		} catch (Exception e) {
			throw new JadxRuntimeException("Failed to update temp root directory", e);
		}
	}

	private static Path createTempRootDir() {
		try {
			Path dir = Files.createTempDirectory(JADX_TMP_INSTANCE_PREFIX);
			dir.toFile().deleteOnExit();
			return dir;
		} catch (Exception e) {
			throw new JadxRuntimeException("Failed to create temp root directory", e);
		}
	}

	public static List<Path> listFiles(Path dir) {
		try (Stream<Path> files = Files.list(dir)) {
			return files.collect(Collectors.toList());
		} catch (IOException e) {
			throw new JadxRuntimeException("Failed to list files in directory: " + dir, e);
		}
	}

	public static List<Path> listFiles(Path dir, Predicate<? super Path> filter) {
		try (Stream<Path> files = Files.list(dir)) {
			return files.filter(filter).collect(Collectors.toList());
		} catch (IOException e) {
			throw new JadxRuntimeException("Failed to list files in directory: " + dir, e);
		}
	}

View on GitHub (pinned to e738a26571)

Solutions

1. Set -Djava.io.tmpdir to a known-writable directory: java -Djava.io.tmpdir=/path/to/writable/dir ...
2. Verify /tmp exists, is writable, and has free space/inodes: ls -ld /tmp && df -h /tmp && df -i /tmp.
3. If running in a container, mount a writable tmpfs or volume at /tmp.
4. Check OS-level security policy (SELinux/AppArmor) is not blocking directory creation.

Example fix

// before — relies on default /tmp which may be unwritable
java -jar jadx.jar input.apk

// after — point tmpdir to a writable location
java -Djava.io.tmpdir=/var/tmp/jadx -jar jadx.jar input.apk

// Cannot easily validate at runtime since this fires at class-load time.
// Pre-launch check: verify java.io.tmpdir is writable before loading FileUtils.
public static void checkSystemTempDir() {
    Path tmp = Path.of(System.getProperty("java.io.tmpdir"));
    if (!Files.isDirectory(tmp) || !Files.isWritable(tmp)) {
        throw new IllegalStateException("java.io.tmpdir is not writable: " + tmp);
    }
}

// This fires as ExceptionInInitializerError at class load; catch at the outermost level.
try {
    Class.forName("jadx.core.utils.files.FileUtils");
} catch (ExceptionInInitializerError e) {
    if (e.getCause() instanceof JadxRuntimeException) {
        System.err.println("Fatal: cannot create temp root. Set -Djava.io.tmpdir to a writable dir.");
        System.exit(1);
    }
}

When it happens

Trigger: Loading FileUtils for the first time when java.io.tmpdir is unwritable, does not exist, is full (no inodes), or the process lacks permission. The JVM's -Djava.io.tmpdir was set to an invalid path. This fires at class initialization, so it can crash the entire application before any user code runs.

Common situations: Running jadx in a locked-down container or CI runner where /tmp is mounted read-only or tmpfs is exhausted. Setting -Djava.io.tmpdir to a path that doesn't exist. An inode-exhausted filesystem. SELinux/AppArmor denying directory creation under /tmp.

Related errors

• Failed to create temp directory
• Failed to update temp root directory
• Failed to create temp directory with suffix: ${prefix}
• Can't create directory ${dir}
• Failed to delete directory ${dir}

AI-assisted analysis of skylot/jadx@e738a26571 (2026-08-14). Data as JSON: /api/errors/4eb51c4d8ba37208. Report an issue: GitHub.