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Optional MiSTer kernel fix

For slow exFAT folder scanning after the September 7, 2026 MiSTer Linux update.

Optional and unofficial, separate from Degauss. Installation and restoration work offline.

For the September 7 release only. The installer checks compatibility and backs up your original kernel automatically.

Install the fix

Have a computer and SD-card reader available for recovery. Keep power stable; do not run Update All, Downloader or another installer at the same time.

  1. Copy three items

    Download the exFAT fix ZIP, unzip it and open its Scripts folder. Copy these items into the Scripts folder already on your MiSTer SD card:

    • Install_exFAT_Fix.sh
    • Restore_Original_Kernel.sh
    • .degauss-exfat-fix (the whole folder, including its contents)

    The folder may be hidden on your computer. Copy it too. Nothing else from the ZIP needs copying. Keep all your existing files.

  2. Run the installer

    In MiSTer’s Scripts menu, run Install_exFAT_Fix.sh. Confirm using a keyboard; the default answer is No. If a check fails, stop and keep the error message.

  3. Keep a copy of the backup

    The installer verifies the original and replacement kernels. It saves the original here, without overwriting an existing backup:

    linux/degauss-exfat-original-260907.zImage_dtb

    Copy this file to your computer before rebooting.

  4. Restart MiSTer

    Restart only after the installer reports success and your backup is saved. There is no automatic reboot. Check normal startup, storage and connected hardware.

Future updates

Leave official updates enabled. Update All, Downloader settings and the Degauss updater stay unchanged. A newer Linux release can replace this fix; do not reinstall this old package or restore its backup over that newer release.

Compatibility and background

Supports stock release 260907, running 6.18.38-MiSTer. The exact kernel file must match. An identical fix already installed needs no repeat installation. Unknown, other modified or newer kernels are refused; do not bypass that check.

Only linux/zImage_dtb changes. linux.img, modules, the bootloader and your games are untouched. This is not a damaged-card repair tool.

About the fix

The package guide and source information describe this exact version of the separate installer and restoration tools.

The change batches exFAT read-ahead requests. It was merged upstream on September 8. The latest image checked on September 10 was still the September 7 archive.

The Linux release marker stays unchanged. Normal Downloader runs do not reinstall the same release just because this fix is installed. Forced updates and custom databases can differ. Downloader details.

Other options

Waiting for an official fixed image avoids this unofficial installation. The maintainer’s rollback alternative pins the whole Linux system to April 2025, potentially losing newer tools or hardware support; cores still update. Do not combine the two approaches.

Backup and recovery

The saved kernel lets you undo this change. Keep a full card backup too: the kernel backup cannot protect against interrupted writes or guarantee every peripheral works.

If MiSTer starts normally

Run Restore_Original_Kernel.sh from Scripts and confirm. Restart after success. A missing or invalid backup stops restoration.

If MiSTer will not boot

Power off MiSTer and connect its SD card to your computer. On the unchanged September 7 installation, copy the verified backup from step 3 back to linux/zImage_dtb. Safely eject the card before restarting.

If Linux has since changed or the backup cannot be verified, use the official recovery guide instead. If you cannot recover the card with a computer, wait for the official fix.