If your Antminer is stuck in a bad state, reflashing can be one of the fastest ways to get it working again. But that only applies if the miner still supports microSD card recovery.
With UMC OS, the critical detail is the recovery image being used. If a miner has already been updated to the latest Bitmain stock firmware, microSD card recovery is blocked and that path is no longer available. If the miner is running a third-party custom firmware, however, it can still be reflashed by microSD card as long as the recovery process uses Compatible Bitmain old stock firmware.
That is why this guide is not a general firmware upgrade tutorial. It is a recovery and reflash guide for supported miners that still have an open microSD recovery path. For Bitcoin Mining operators, that distinction matters: once a miner is updated to the latest Bitmain stock firmware, there is no microSD card-based way back.
Important warning before you begin
Do not update to the latest Bitmain stock firmware if you may need to recover or reflash the miner later.
Once a miner is on that newer stock firmware, microSD card access is blocked. That means the reflash method in this guide will no longer work. To remain recoverable, the miner must still be on:
- A compatible Bitmain stock firmware
- February 2024 or prior
- July 2024 or newer up to February 2025
- A third-party custom firmware
When this reflash guide applies
This guide is for miners that:
- are stuck in a bad state
- need to be reflashed
- are still on a recoverable firmware base
What you need
Before starting, make sure you have:
- A computer
- A microSD card
- A card reader
- Disk imaging tool e.g. balenaEtcher
- Compatible Bitmain Old Stock Firmware Version from the following:
- February 2024 or prior
- July 2024 or newer up to February 2025
- RigRunner
- A miner that is still recoverable
The curent reflash workflow
The reflash process is now:
- Download a disk imaging tool such as balenaEtcher.
- Format the microSD card as MS-DOS (FAT).
- Flash the microSD card with Compatible Bitmain old stock firmware.
- Insert the microSD card into the miner and flash the old stock firmware.
- Once that is complete, download RigRunner.
- Use RigRunner to install the latest version of UMC OS.
Step 1: Download disk imaging tool
Start by downloading disk imaging tool. balenaEtcher is the one that we recommend. This is the tool used to write the recovery image to the microSD card.
For users searching for Custom Antminer Firmware recovery steps, this is the first part of preparing the reflash process.
Step 2: Prepare the microSD card
Format the microSD card as MS-DOS (FAT).
Mac
- Insert the microSD card into the card reader
- Connect card reader to the computer
- Open Disk Utility
- Select the card
- Click Erase
- Choose MS-DOS (FAT)
- Choose Master Boot Record (MBR) if shown
- Click Erase
Windows
- Insert the microSD card into the card reader
- Connect card reader to the computer
- Open File Explorer
- Right-click the card and select Format
- Choose FAT32
- Click Start
Step 3: Flash the microSD card with Compatible Bitmain Old Stock Firmware
Use balenaEtcher or other disk imaging tool to write Compatible Bitmain Old Stock Firmware to the microSD card.
The version matters. It must be a Bitmain stock firmware version from the following timeline:
- February 2024 or prior
- July 2024 or newer up to February 2025
This step is important because the microSD card is not being loaded with UMC OS directly. Instead, it is being loaded with the older stock firmware needed to recover the miner and move it back into a usable state.
Step 4: Insert the SD card into the miner and flash the old stock firmware
Insert the microSD card into the miner via SD card reader and use it to flash the old stock firmware.
This is the recovery stage. The purpose is to get the miner out of its bad state and back onto a recoverable stock firmware version.
For Bitcoin Mining operators, this is the practical difference between a miner that can still be repaired through firmware and one that has already been locked out by a newer stock update.
Step 5: Download RigRunner
Once the old stock firmware has been installed successfully, download RigRunner.
RigRunner is the tool used for the next step: installing the latest UMC OS.
Step 6: Use RigRunner to install the latest UMC OS
Open RigRunner and use it to install the latest version of UMC OS.
This is the final step in the recovery workflow. The old Bitmain stock firmware acts as the bridge, and RigRunner is what moves the miner from that bridge state to the latest Bitcoin Mining Firmware from ePIC.
Why this workflow exists
This process exists because the goal is recovery, not just installation.
If a miner is stuck in a bad state, a direct install may not be the right answer. The practical fix is to first reflash the machine back to an older, recoverable Bitmain stock firmware, then install UMC OS cleanly through RigRunner.
That makes this guide more useful than a generic firmware article. It answers the real question readers have:
How do I recover and reflash an Antminer when it is in a bad state, but still recoverable?
Who this guide is for
This tutorial is useful for:
- Miners stuck in a bad firmware state
- Operators recovering machines already on older stock firmware
- Operators recovering machines already on third-party custom firmware
- Users trying to install the latest UMC OS without losing the recoverable path first
It is not meant for miners that have already been updated to September 2025 or newer Bitmain stock firmware, because those miners no longer support this microSD card recovery method.
Common mistakes to avoid
Updating to the latest Bitmain stock firmware
This is the biggest mistake. Once the miner is on September 2025 or newer Bitmain stock firmware, microSD card reflashing is no longer possible.
Assuming every miner can be recovered
This guide only applies to miners that are still on older stock firmware or third-party custom firmware.
Flashing UMC OS directly to the microSD card in this workflow
In this process, the microSD card is first used for Bitmain Old Stock Firmware. UMC OS is then installed afterward through RigRunner.
Treating this as a normal firmware upgrade
This is a recovery tutorial for miners in a bad state. It is not a routine firmware update article.
FAQ
When can I use this reflash method?
You can use it when the miner is in a bad state but is still recoverable. That means it must still be on older Bitmain stock firmware or third-party custom firmware.
When will this method not work?
It will not work if the miner has already been updated to September 2025 or newer Bitmain stock firmware, because microSD card access is blocked.
What do I flash to the microSD card?
Flash with a Compatible Bitmain Old Stock Firmware.
When do I install UMC OS?
After the old stock firmware has been flashed successfully, use RigRunner to install the latest version of UMC OS.
Is this a standard upgrade tutorial?
No. This is a recovery and reflash tutorial for miners that are stuck in a bad state but still have an available reflash path.
Final takeaway
If an Antminer is stuck in a bad state, reflashing may still be possible — but only if the miner remains recoverable. To use this method, the miner must still support microSD recovery, and the reflash must use Compatible Bitmain old stock firmware within the supported compatibility ranges. If the miner has already been updated to the latest Bitmain stock firmware, microSD card reflashing is blocked and this recovery path is gone. For recoverable miners, the workflow is simple: format the microSD card, flash it with Compatible Bitmain old stock firmware, reflash the miner, then use RigRunner to install the latest version of UMC OS.
