I copied 10 videos to a 64gb flash drive fine. Everything copied over fine. Had another set of 10 videos I needed to copy and after that. Started copying the second batch of ten and after the first video (and probably half way through the second) it stopped and said 'Error opening file '/media/micah/USB20FD/(the video)': Read-only file system'.

How can this happen when it's half way through copying a file?

It wouldnt happen half-way through unless there was no more free space on the drive. If you just type the command "mount" or cat your /etc/mtab file you can see the mounts and their options, which should have either an ro or rw for read only or read write.

So you either :

1) Did not copy the files to the USB drive when you thought you had and it was read only the entire time
2) Somehow re-mounted the USB drive, either by unplugging it and plugging it back in or manually remounted it.
3) Filled up the usb drive and it has no more free space(although the error message usually indicates this).

I have had USB devices go read-only on me, particularly my podplayer, which gets a lot of mounting and remounting as I remove listened-to podcasts and add new ones every day, though I can't recall it happening in the middle of copying a file--it might have, but I can't be certain. I have had happen while copying a series of files.

Unmounting, removing, and remounting it has fixed the problem for me. It happens very infrequently and I've never been inconvenienced enough to try to figure out why it happened.

Just curious, how big are the videos and what FS on the drive? I have seen this copying files larger than 4GB to a FAT based drive.

Hi there,

that was my first idea, too, but I think this produces a different error condition. "Not enough space" or something like that, IIRC.

However, I occasionally had this effect too - a USB drive (a normal HDD) that mounted fine, I copied a large amount of data to it, and in mid-copy the process stalled and complained about the target being read-only.
I investigeted that, and found out that from time to time the USB device disconnected and reconnected again after fractions of a second. That disconnection was so short that it wasn't even reported by the desktop, but since it happened during a write access, it left file system errors and therefore the file system was re-mounted read-only.

I finally found out that the reason was a bad USB plug that would lose contact from time to time when the cable was moved.

[X] Doc CPU