Why does my SD card change to readonly when I mounted it as readwrite?

Question

I've got an SD card mounted on a ip camera, which runs on linux. I set the videos to record on to the SD card, but after a few days, all my cameras' SD cards stopped recording and I noticed it was because they were all mounted as readonly. When I mount them back as readwrite, they turn into readonly right after.

I suspected it was this batch of SD cards that I bought cheap from ebay, so I tried putting them into a USB adapter into Windows, and it can read and write just fine -- I tested it by filling it with a bunch of random videos, and then copying them back out.

Here's the entry in mount -v

/dev/hd1 on /tmp/hd1 type vfat (ro,relatime,fmask=0022,dmask=0022,codepage=cp437,iocharset=iso8859-1,shortname=mixed,errors=remount-ro)

Any idea what's going on? This is happening to all 4 of my cameras and SD cards.

Answer 1

Note that you have errors=remount-ro specified as an option. Thus if an error occurs, you'll that find your media has become read-only.

You can replace this with errors=continue to ignore such errors. You probably don't want to.

If you notice it soon enough, you can check dmesgor other logging sources (journalctl?) on the "bad" system to see if such errors have occurred.