Dual Boot ROMs on Galaxy S8 & Note 8

This guide shows you how to set up a dual-boot environment on the Samsung Galaxy S8 or Note 8, letting you run two different custom ROMs (or a ROM and the stock firmware) on the same device. You’ll need an unlocked bootloader, a custom recovery, and a bit of patience. The process uses a tool called DualBootPatcher, which modifies ROM zip files so they can coexist without overwriting each other.

What You’ll Need

An unlocked bootloader (Exynos models can be unlocked via OEM unlock in Developer Options; Snapdragon models may not be unlockable).
A custom recovery installed (e.g., TWRP).
A PC with USB cable and Odin (for flashing recovery if needed).
Two ROM zip files you want to dual-boot (one as primary, one as secondary).
DualBootPatcher app (latest version) – download the APK and the recovery zip from its official source.
At least 2–3 GB of free internal storage for the secondary ROM.
Backup of your current data (the process wipes the device).

Step-by-Step

Back up everything. Connect your phone to PC, copy all important files to your computer, and make a full TWRP backup (System, Data, Boot, EFS) to an external SD card.
Unlock the bootloader (if not already). On Exynos Galaxy S8/Note 8, go to Settings > About Phone > Software Information, tap Build Number 7 times to enable Developer Options. Then go to Settings > Developer Options and enable “OEM unlocking”. Reboot to bootloader (hold Volume Down + Bixby + Power), then long-press Volume Up to confirm unlock. This wipes your phone.
Install TWRP recovery. Download the TWRP image for your exact model (e.g., SM-G950F for S8, SM-N950F for Note 8). Boot your phone into Download mode (Volume Down + Bixby + Power). Use Odin on PC to flash the TWRP .tar file in the AP slot. After flashing, immediately reboot to recovery (Volume Up + Bixby + Power) to prevent stock recovery from overwriting TWRP.
Install DualBootPatcher app. Boot into your current ROM (or after a fresh stock setup), install the DualBootPatcher APK. Open the app and grant root permissions.
Patch your secondary ROM zip. In the app, tap the “+” icon, select the ROM zip file you want as secondary. Choose “Secondary” as the install location. Tap the checkmark to patch the zip. This creates a modified zip in the same folder (usually named with “-patched” suffix).
Flash the patched zip. Reboot to TWRP recovery. Flash the patched zip file. It will install to the secondary slot. Do NOT reboot yet.
Flash the DualBootPatcher recovery zip. In TWRP, go to Install, select the DualBootPatcher recovery zip (the one you downloaded), and flash it. This adds the necessary scripts to switch between ROMs.
Reboot to primary ROM. Reboot the phone normally. Your primary ROM should boot as usual.
Switch to secondary ROM. Open the DualBootPatcher app. Tap the “ROMs” tab – you’ll see both primary and secondary. Tap the secondary ROM and select “Reboot to this ROM”. The phone will reboot into the secondary ROM.
Set up the secondary ROM. Go through the initial setup of the secondary ROM. You may need to sign in to your Google account again. Install your apps as needed.

Common Mistakes

Wrong model firmware: Flashing a ROM or recovery for the wrong variant (e.g., Snapdragon vs Exynos) can hard-brick your device. Always verify your exact model number in Settings > About Phone.
Skipping the OEM unlock step: On Exynos models, forgetting to enable OEM unlock before flashing TWRP will cause the phone to fail to boot or revert to stock recovery.
Not flashing the DualBootPatcher recovery zip: Without this, the app cannot switch ROMs – you’ll be stuck on the last ROM you flashed.
Using too little storage: Secondary ROMs need several GB. If you run out of space, the patch or flash will fail.
Wiping data between ROMs: Don’t wipe data in TWRP after setting up dual boot – it may remove the secondary ROM’s data and cause boot loops.

Tips

Keep both ROMs on the same Android version (or at least the same major version) to avoid compatibility issues with the shared /data partition.
Use a fast SD card if you plan to store the secondary ROM on the external SD (DualBootPatcher supports this). It’s slower but saves internal space.
After flashing a new primary ROM, you may need to re-patch and re-flash the secondary ROM because the primary ROM’s kernel may change the boot structure.
Always keep a full TWRP backup of both ROMs after setup – it makes restoring much easier.
If you want to remove dual boot, simply flash a new ROM zip (primary) via TWRP and wipe the secondary slot in the app.

Troubleshooting

Phone boots to recovery instead of system: This usually means the boot image is corrupted. In TWRP, go to Wipe > Advanced Wipe, select Dalvik/ART Cache and Cache, then reboot. If it still fails, re-flash the primary ROM zip (without wiping data).
Secondary ROM won’t boot (bootloop): Boot into TWRP, wipe cache and Dalvik, then try again. If it persists, the ROM may not be compatible with dual boot – try a different ROM or a different Android version.
“No ROMs found” in the app: Ensure the DualBootPatcher recovery zip was flashed successfully. Re-flash it via TWRP.
Storage space runs out during patch: Free up space on /sdcard by deleting old zips or moving them to a PC. Then re-patch.
App force closes: Clear the app’s data in Settings > Apps, then reopen and grant root again. You may need to re-add the ROMs.
After switching to secondary, primary ROM is gone: This is normal – the app switches the active slot. To return, open the app, select the primary ROM, and reboot.

Frequently Asked Questions

Can I dual boot on a Snapdragon Galaxy S8?

No. Snapdragon variants (US/Canada) have locked bootloaders that cannot be unlocked, so custom recovery and dual boot are not possible. Only Exynos models (international) support this.

Will dual booting void my warranty?

Unlocking the bootloader and flashing custom recovery voids Samsung’s warranty. You can restore stock firmware later, but the bootloader unlock status may remain flagged.

Can I use the same Google account on both ROMs?

Yes, you can sign in with the same Google account on both, but note that app data and settings are separate for each ROM.

Does dual booting affect battery life?

No, only one ROM runs at a time. The inactive ROM is powered off, so it uses no battery.

Can I update one ROM without affecting the other?

Yes, you can update the primary ROM normally via OTA or flashing. For the secondary ROM, you need to patch the new update zip and flash it as secondary again.

What happens if I factory reset from the secondary ROM?

Factory reset from the secondary ROM will wipe the data of the secondary ROM only. The primary ROM’s data is stored in a separate partition and remains intact.

Method: the standard formula for this calculation, rounded as each result states. See how the calculators work or report an error.

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