How to free blocked space on a muOS SD card (Anbernic RG40XXH)

Sometimes an SD card says it’s much fuller than the files on it. On a muOS handheld like the Anbernic RG40XXH you may see, for example, 21 GB used while all your folders add up to only 6 GB. The missing space isn’t hidden files: it’s blocked space, marked as used on the card although no file holds it. This guide shows how to get it back.

Written for: Anbernic RG40XXH · muOS 2601.0 Jacaranda · Wi-Fi Transfer 2.0.0.

How do you know?

Wi-Fi Transfer measures it for you. Open the page on your phone or PC: if more than 1 GB is blocked, the card’s tab shows a note like “About 15.0 GB on SD card 1 is blocked by damaged or lost space that no folder shows.”

Why it happens

The card keeps a list of which parts of it are in use. If a copy or a delete is cut off halfway, the list can keep parts marked as used that no file points to any more. Common causes:

• The battery ran out, or the handheld froze, while files were being copied or deleted.
• The card was taken out, or the handheld turned off, during a copy.
• A card reader was unplugged without ejecting the card first.

Usually your games and saves are fine; the space just can’t be used. It doesn’t fix itself, and it can’t be repaired safely on the handheld, because muOS runs from that card. A disk check on a Mac or PC frees it in a few minutes.

Before you start

• Copy your saves (MUOS/save on SD card 1) to your computer, or make a full backup of the card. A disk check is safe, but a card with errors deserves a copy first.
• Turn the handheld off (not sleep), take out the card, and put it in your computer with a card reader.
• The computer may show only one drive: the large partition that holds your games. That’s the one to check. If Windows offers to format another part of the card, press Cancel.

On a Mac

1. Open Disk Utility (Applications → Utilities).
2. Choose View → Show All Devices, then select the card’s large volume (the one with ROMS and MUOS on it).
3. Click First Aid, then Run, and confirm.
4. When it says the check is complete, eject the card (the ⏏ button) before taking it out.

On Windows

1. Open File Explorer → This PC.
2. Right-click the SD card’s drive → Properties → Tools → under Error checking, click Check.
3. Choose Scan and repair drive (if Windows says the drive doesn’t need a scan, choose Scan drive anyway).
4. When it’s done, eject the card (right-click → Eject) before taking it out.

Prefer the command line? In a Command Prompt opened as administrator, run chkdsk E: /f, replacing E: with the card’s drive letter.

On Linux

Find the card’s exFAT partition with lsblk -f, unmount it, and check it with the fsck.exfat tool from exfatprogs:

sudo umount /dev/sdX2
sudo fsck.exfat -y /dev/sdX2

Replace /dev/sdX2 with the exFAT partition lsblk shows. Double-check it’s the SD card.

Afterwards

Put the card back in the handheld and turn it on. Open Wi-Fi Transfer: the note is gone, and the line at the top shows more free space. A full backup also gets smaller, because blocked space was copied too.

If the note is still there after a check, the card may be wearing out. Copy your saves, and consider moving to a new card with a full backup and restore.

Keep it from coming back

• Don’t let the battery run flat while copying, and keep the handheld on until a copy has finished.
• Turn the handheld off before taking the card out.
• Always eject the card on your computer before unplugging it.

Questions? Email feedback@pocketkode.com.

PocketKode is not affiliated with muOS, Anbernic, Apple or Microsoft.