MuntashirAkon/AppManager · error · BackupException

Data restore is requested but there are no data files for in

Error message

Data restore is requested but there are no data files for index ${i}.

What it means

During signature/integrity verification in restoreData, if BackupFiles.BackupItem.getDataFiles(i) returns an empty array for any data directory index, this BackupException is thrown. It means the backup metadata claims a data directory exists (mBackupMetadata.dataDirs.length entries) but no corresponding backup files (tar, etc.) were found on disk.

Source

Thrown at app/src/main/java/io/github/muntashirakon/AppManager/backup/RestoreOp.java:492

                throw new BackupException("Failed to rename KeyStore files", e);
            }
        }
        Runner.runCommand(new String[]{"restorecon", "-R", keyStorePath.getFilePath()});
    }

    private void restoreData() throws BackupException {
        // Data restore is requested: Data restore is only possible if the app is actually
        // installed. So, check if it's installed first.
        if (mPackageInfo == null) {
            throw new BackupException("Data restore is requested but the app isn't installed.");
        }
        if (!mRequestedFlags.skipSignatureCheck()) {
            // Verify integrity of the data backups
            String checksum;
            for (int i = 0; i < mBackupMetadata.dataDirs.length; ++i) {
                Path[] dataFiles = mBackupItem.getDataFiles(i);
                if (dataFiles.length == 0) {
                    throw new BackupException("Data restore is requested but there are no data files for index " + i + ".");
                }
                for (Path file : dataFiles) {
                    checksum = DigestUtils.getHexDigest(mBackupInfo.checksumAlgo, file);
                    if (!checksum.equals(mChecksum.get(file.getName()))) {
                        throw new BackupException("Data file verification failed for index " + i + "." +
                                "\nFile: " + file +
                                "\nFound: " + checksum +
                                "\nRequired: " + mChecksum.get(file.getName()));
                    }
                }
            }
        }
        // Force-stop and clear app data
        PackageManagerCompat.clearApplicationUserData(mPackageName, mUserId);
        // Restore backups
        for (int i = 0; i < mBackupMetadata.dataDirs.length; ++i) {
            String backupDataDir = mBackupMetadata.dataDirs[i];
            if (backupDataDir.equals(BackupManager.DATA_BACKUP_SPECIAL_ADB)) {

View on GitHub (pinned to 0152f468fc)

Solutions

  1. Re-create the backup; the existing one is incomplete and cannot pass verification.
  2. Copy the missing data backup files for index i into the backup directory.
  3. Check that external storage (SD card) containing the data backup is mounted.
  4. If the data dir was intentionally skipped, re-create metadata without that dataDirs entry or skip signature check (skipSignatureCheck) — not recommended.

Example fix

// before: restoring from a partial backup
ew BackupManager(...).runRestore(); // throws for missing index files
// after: validate backup completeness first
for (int i = 0; i < metadata.dataDirs.length; i++) {
    if (backupItem.getDataFiles(i).length == 0) {
        throw new IllegalStateException("Backup incomplete: missing data files for index " + i);
    }
}
runRestore();
Defensive patterns

Strategy: validation

Validate before calling

for (int i = 0; i < metadata.dataDirs.length; i++) {
    if (backupItem.getDataFiles(i).length == 0)
        throw new IllegalStateException("Incomplete backup: no data files for index " + i);
}

Type guard

boolean hasAllDataFiles(BackupItem item, int dirCount) {
    for (int i = 0; i < dirCount; i++) if (item.getDataFiles(i).length == 0) return false;
    return true;
}

Try / catch

try { runRestore(); } catch (BackupException e) {
    if (e.getMessage().startsWith("Data restore is requested but there are no data files")) {
        promptUserForCompleteBackup();
    } else throw e;
}

Prevention

When it happens

Trigger: The backup directory is missing its data .tar/.tar.gz files for index i while metadata lists that data dir; files were deleted/moved manually; metadata (meta files) edited to add a dataDir without backing files; external-storage data backup located on an unmounted SD card.

Common situations: Partial backup (process killed mid-backup) leaving metadata but no data archives; user copied only some files when moving backups between devices; data files stored on removable storage that isn't mounted.

Understand the failure class

Background: "File not found" and ENOENT errors: why libraries can't find a file that should exist — this error's family across 50 libraries.

Related errors

AI-assisted analysis of MuntashirAkon/AppManager@0152f468fc (2026-09-12). Data as JSON: /api/errors/1c2a3631489f941d. Report an issue: GitHub.