I have a SamsungGalaxy S3 (32GB Verizon version, not rooted) with a 64GB external SD card.

I use the external card only for music, which I load from my computer. Several times now I have lost files from the external card. Is there any way I can force the S3 to mount the external card as "read-only"?

Ideally, a widget that would allow me to toggle the mount from RO to RW and back would be perfect, but any way to mount it as RO will satisfy my need to protect the data on the card.

  • How comes you've lost data from the SD card? What happened? Maybe your real question is how to prevent this (see: XY problem)?
    – Izzy
    Jan 26, 2013 at 11:32

2 Answers 2


I disagree with Liam's answer.

Its possible with root, you can just use the "root explorer" app on play store and navigate to /storage/extSdCard/ and on the top, click the "Mount R/O" button to mount the drive as read only.

Surely if you know the linux codes, you should be able to make it into a widget for it :p (one line or so)

(I think there's an app that makes widgets from busybox codes) - that could be your answer

  • Please note: Answers can be sorted in a number of different ways. "Previous poster" has no context. Click the "share" link on the other answer and copy the URL so you can make a link in your answer.
    – ale
    Jan 30, 2013 at 16:18

Unfortunately, there is no way to do this, even if you were to be rooted. The sdcard filesystem doesn't support being mounted as RO.

If you try to mount it, you will get an error.

As well as this, the only way to mount it RO, if there was one, would require root.

  • Do you have a source for your statement "The sdcard filesystem doesn't support being mounted as RO." ? Googling "sd card read only android" (without quotes) shows a lot of instances where this is the case; showing that it is supported, even if it is undesired.
    – Dylan Yaga
    Jan 30, 2013 at 18:06

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