A Nandroid backup is a direct byte-for-byte copy of an Android device's NAND flash memory partitions, creating a complete system image. This backup is typically performed from a custom recovery environment like TWRP and is invaluable for system restoration after software malfunctions, failed modifications, or to revert to a known-stable state.
Core Components of a Nandroid Backup
Nandroid backups capture critical data from various partitions. Key partitions usually included are:
- /boot: Contains the kernel and ramdisk, essential for the device to start.
- /system: Encompasses the Android operating system, pre-installed applications, and system libraries.
- /data: Stores user-installed applications, their data, user settings, and personal files.
- /cache: Holds temporary system and application data for faster access. (Often optional for backup)
- /efs or /persist: (Device-specific) Contains vital device identifiers like IMEI, MAC addresses. Crucial to back up to prevent loss of connectivity.
Prerequisites for Nandroid Backups
Before creating a Nandroid backup, two primary conditions must be met:
- Unlocked Bootloader: The device's bootloader must be unlocked to allow flashing custom software.
- Custom Recovery: A custom recovery environment, such as TWRP (Team Win Recovery Project), must be installed. Stock recovery typically does not offer Nandroid backup functionality.
Creating a Nandroid Backup
The creation process is executed within the custom recovery:
Boot into Recovery: Power off the device. Reboot it into recovery mode by pressing and holding the specific hardware key combination for your device model (e.g., Power + Volume Down).
Navigate to Backup: Once in the custom recovery interface, find and select the 'Backup' option.
Configure Backup Options:
- Select the partitions to include. It is highly recommended to back up /boot, /system, /data, and /efs (or its equivalent).
- Choose the storage location: internal storage, external SD card, or USB OTG (if supported).
- Optionally, set a custom name for the backup for easier identification. Some recoveries allow compression.
Initiate Backup: Swipe or tap the confirmation control to begin the backup process. This can take several minutes depending on the size of the selected partitions and storage speed.
Verify Completion: Ensure the recovery reports a successful backup operation. The backup files will be stored in a designated folder (e.g., TWRP/BACKUPS/[DeviceSerialNo]/[BackupName]) on the chosen storage medium.
Restoring from a Nandroid Backup
Restoration also occurs within the custom recovery:
Boot into Recovery: Access the custom recovery environment as previously described.
Navigate to Restore: Select the 'Restore' option from the main menu.
Select Backup: Choose the specific Nandroid backup file you wish to restore from the list of available backups.
Select Partitions: Choose which partitions from the backup you want to restore. For a full system revert, select all major partitions backed up previously.
Initiate Restore: Confirm the selection to start the restoration process. This will overwrite the current data on the selected partitions with the data from the backup.
Reboot System: After the restore completes successfully, reboot the device. The system should boot into the state it was in when the backup was created.
Important Considerations
- Storage Space: Nandroid backups are large, often consuming several gigabytes. Ensure sufficient free space on your target storage medium.
- Battery Level: Always ensure your device has a significant battery charge (at least 50% recommended) before starting a backup or restore to prevent interruption due to power loss, which could lead to a bricked device.
- External Storage: It is strongly advised to copy Nandroid backups to an external source like a PC, external hard drive, or cloud storage. Relying solely on internal storage is risky; if the device fails to boot or internal storage gets corrupted, the backup may be lost.
- Frequency: Create backups regularly, especially before flashing new ROMs, kernels, mods, or performing any significant system-level changes.
- Backup Integrity: Some custom recoveries offer an option to verify backup integrity after creation. Use this if available.
- Compatibility: Nandroid backups are generally device-specific and sometimes build-specific. Restoring a backup made on a different device model or a significantly different Android version/ROM can lead to bootloops or instability.
