Xiaomi Redmi firmware S2 Fastboot: A Complete Guide to 2026

Xiaomi Redmi S2 (codename ysl is a budget smartphone of 2018, which is still popular due to its reliability and customization. MIUI They stop coming out, and users face slowdowns, bugs, or the desire to install an alternative firmware. Fastboot is one of the most reliable ways to update or restore a device, but the process requires accuracy and understanding of the nuances.

In this article, you will find a step-by-step guide to the current requirements of 2026: from unlocking the bootloader to choosing the right version of the firmware and solving typical errors. S2 can not be flashed through the Mi Flash Tool, how to avoid a "brick" (breakdown of the device) and what to do if the smartphone is getting stuck on the Mi logo. Particular attention will be paid to bypassing the restrictions of Xiaomi on unlocking the bootloader for old models - this is a key point, which many are silent about.

1. Firmware Preparation: What to Do Before Starting

Fastboot firmware is a process that requires pre-production, and without it, you risk getting a brick instead of a work phone, and let's start with the most important thing: unlocking the bootloader.

Xiaomi Redmi. S2 (Like all the brand devices, the bootloader is locked by default, which means that it is not possible to simply flash custom or even official firmware, the unlock procedure takes up to 720 hours (30 days) of waiting after linking the Mi Account to the device:

• 🔓 Xiaomi account must be created in advance and confirmed by phone number/email. Use the same account that is linked to your phone.
• ⏳ The waiting timer begins after the first attempt to unlock through the Mi Unlock Tool. You can not interrupt it - otherwise the counter will reset.
• 📱 Version. MIUI must be at least 9.5.3.0 (for Redmi) S2). On older versions, unlocking may not work.
• 🔌 Battery charge at least 60 percent. Firmware at low charge is fraught with failures.

Also prepare:

• 💻 Computer on Windows 7/10/11 (64-bit). MacOS or Linux may have driver problems.
• 🔌 Original. USB-Cheap cables often don't transmit data in Fastboot mode.
• 📁 Firmware for your model (more on this in the next section).
• 🛠️ Mi Flash Tool, Mi Unlock Tool, Qualcomm Drivers.

⚠️ Note: If you are buying a Redmi S2"hand, make sure the previous owner untie his Mi Account from the device, otherwise unlocking will not be possible without his data.

2. firmware selection: official MIUI vs custom builds

The choice of firmware not only determines the functionality of the phone, but also its stability. S2 available:

Where do I download the firmware?

• 🌍 Official. MIUI Fastboot: Xiaomi website (choose the version for ysl).
• 🔗 MIUI EU: SourceForge (Look for ysl in the title).
• 📱 Custom firmware: XDA Developers (Section for Redmi) S2).

Important: The firmware version must match your device's code. S2 Install firmware for another model (for example, ysl_global instead of ysl, it will lead to errors or a blink.

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Before downloading the firmware, check its hash sum (MD5) utility-wise MD5 Checker.This will help to avoid installing a corrupted file.

3. Unlock the bootloader: bypass the limitations of Xiaomi

Unlocking the bootloader is the most difficult step, especially for older models like Redmi. S2. Xiaomi has tightened the rules, and now even after waiting 720 hours, there can be errors:

1. Install the Mi Unlock Tool (the latest version can be downloaded here).
2. Turn on the developer mode on the phone: go to Settings → About Phone → MIUI version and tap 7 times on the build number.
3. B Settings → Additionally. → For developers, activate: 🔓 Unlocking OEM (It may not be available on some versions. MIUI). 🔌 Debugging by USB.

Connect your phone to your PC, launch the Mi Unlock Tool, and log in to your Mi Account.

If you see a "Couldn't unlock" or "Current account is different from the account info on the device" error, try:

• 🔄 Restart your phone and PC.
• 🔌 Use the other USB-port (preferably) USB 2.0).
• 📱 Manually link the account to Settings → Mi Account → Synchronization.

⚠️ If the Mi Unlock Tool is not available, "Device is locked. OEM unlock" and the option to unlock OEM There is no setup, so your version is MIUI It's too old. Upgrade to at least MIUI 10 via Recovery.

Once successfully unlocked, the phone will restart with the bootloader unlocked, and you can now start the firmware. But remember, unlocking resets all the data on the device!

4. Step-by-step instruction: firmware via Mi Flash Tool

Now, to the firmware itself, we'll use the Mi Flash Tool, the official Xiaomi utility, and follow the instructions carefully.

Step 1: Install drivers and Mi Flash Tool

• 💾 Download and install the Mi Flash Tool.
• 🔧 Install Qualcomm drivers (if you haven’t done it before).
• 📂 Unpack the downloaded firmware (.tgz or.zip) into a folder without Cyrillic characters (for example, C:\MIUI\ysl).

Step 2: Transfer your phone to Fastboot mode

1. Turn off Redmi. S2.
2. Press Volume Down + Power and hold for 10 seconds until the hare appears in the hat-out-of-the-box (Fastboot logo).
3. Connect the phone to the PC.

Step 3: Firmware via Mi Flash Tool

1. Run the Mi Flash Tool on behalf of the administrator.
2. Click Select and point the way to the folder with unpacked firmware.
3. Select firmware mode at the bottom: Clean all – complete cleaning (recommended when changing firmware). Clean all and lock – cleaning + Save user data - Save user data - data storage (not always stable).

Refresh

COM-port

Flash

If it goes well, the phone will reboot to a new firmware. If it doesn't, read the error section.

5. Typical errors and their solutions

Fastboot firmware doesn't always go smoothly, but here are the most common bugs and ways to fix them:

If the Mi Flash Tool gives an error "flash not done", run in the command line (in the folder from fastboot):

fastboot oem edl

This will put the phone in emergency mode (EDL), You can then repeat the firmware via the Mi Flash Tool or QFil.

⚠️ Warning: If after firmware the phone doesn't turn on and doesn't respond to buttons, don't panic.Plug it into charging for 30 minutes, then try going to Fastboot (Loudness down). + If it doesn't work, you'll need firmware through EDL using boxing (such as UFi Box or EasyJTAG).

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If the firmware is interrupted in the middle, never disconnect the phone from the PC! wait for the process to complete or force the device to restart in Fastboot, then try again.

6.Steaming of custom Recovery (TWRP) and alternative firmware

If you want to install custom firmware (like LineageOS or Pixel Experience), you need to flash it first. TWRP Recovery for Redmi. S2 process:

Step 1. Download TWRP

• 📥 Official version TWRP For ysl, you can find it on the website. TWRP.
• 🔗 Alternative builds (for example, with encryption support) look at XDA.

Step 2: Install TWRP via Fastboot

1. Put your phone in Fastboot mode.
2. Connect to your PC and execute the command: fastboot flash recovery twrp-3.7.0_9-0-ysl.img (Replace the file name with the current one).
3. Immediately after that, do: fastboot boot twrp-3.7.0_9-0-ysl.img It'll load the phone into TWRP without overwriting the default recovery.

Step 3: Custom firmware firmware

• 📁 Place the downloaded firmware (.zip) on the external SD-card or internal memory (if) TWRP sees).
• 🔧 V TWRP Choose the Wipe → Advanced Wipe and mark: Dalvik / ART Cache System Data Cache
• 📥 Return to the main menu, select Install and specify the firmware file.
• ⚙️ After installing the firmware, it is recommended to flash Magisk (for root rights) or Disable Force Encryption (if the firmware does not support encryption).

Not all custom firmware supports (two of them). SIM-maps on Redmi S2. Before installing, check the reviews on the forums.

7.Recovery after a failed firmware (unbrick)

If Redmi S2 You don't have to rush it into service, 90 percent of the time, you can restore it yourself:

Method 1. Firmware through EDL (emergency)

• 🔌 Connect your phone to your PC, press Volume Up. + Volume down and insert cable USB. The device should be identified as Qualcomm HS-USB QDLoader 9008.
• 💾 Download the firmware for EDL (This file is usually a file with the.mbn or.elf extension).
• 🛠️ Use the Mi Flash Tool or QFil to Firmware in Mode EDL.

Method 2: Flashing through Test Point

If the phone is not identified in EDL, You'll need to close the test point. S2:

1. Remove the back cover and battery.
2. Find two contacts with the inscription TP or Test Point (usually near the charging connector).
3. Close them with tweezers or screwdrivers, simultaneously connecting USB-cable.
4. The device should be designated as Qualcomm 9008.

⚠️ Warning: Disassembly of the phone will void the warranty (if it is still valid). If you are not sure about your abilities, contact the service center. EDL In the workshops, it usually does not exceed 1000-1500 ruble.

Method 3: Use of boxes (UFi, EasyJTAG)

If the first two methods didn't work, you'll need a hardware and software package (box).

• 📦 UFi Box – supports most Xiaomi models, including Redmi S2.
• 🔧 EasyJTAG is a more budget option, but requires soldering skills.
• 💻 Medusa Pro – professional solution for service centers.

The cost of firmware through boxing in the service: from 1500 to 3000 rubles. If you plan to do this regularly - it makes sense to buy your box (from 5000 rubles).

8.Optimization after firmware: what to do first

After a successful firmware Redmi S2 It requires additional adjustment:

• 🔄 Reset the settings to factory settings (if you were flashing on top of the old system) and avoid conflicts between old and new files.
• 🔒 Disable unnecessary services: Go to Settings → Annexes → Autostart and disable autostart for unnecessary programs. → Delete Unnecessary Accounts.
• 📵 Set up energy saving: Activate the battery → Power Saving Mode. Turn off Constant Network Search in Settings SIM-map.
• 🛡️ Update Security: Install the latest security patches through Settings → Update. If you've made a custom, check for updates in your firmware settings.

For custom firmware, it is also recommended:

• 🎯 Install Magisk for root rights (if necessary).
• 🔧 Check the operation of sensors (gyroscope, compass) using the Sensor Test application.
• 📡 Manually set up the network if the automatic search is not working.

If it's gone after the firmware. IR-Install the Mi Remote application from APKPure – it will restore functionality.

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After you have custom firmware, be sure to check the camera through the GCam or Open Camera app. On some builds, the main camera may not focus due to the lack of drivers.

FAQ: Answers to Frequent Questions