OK, so it's been a couple months. That thing i was trying to avoid actually happened. My ext3 filesystem has become corrupt. First symptom: media player couldn't find the next audio track - and the book was just getting to the exciting part.

I rebooted, and unmounted the SD card. e2fsck fixed some errors, then aborted with "short read". I thought that meant that there was at least a bad block on the card, but dd could read the entire volume, and 3 runs of badblocks didn't find anything. I ran e2fsck again, and it got further, making some changes. Then it got a segmentation violation. That's repeatable.

I've got a USB SD card adapter, so i mounted the card on my x86 linux desktop machine. It can read the card - dd reads the whole thing (only a little quicker than the n800 can). But e2fsck there says that the magic number is not recognized. Oh. Some byte order problem? I dunno. The Arm is not the same byte order as the x86.

So, i'm back to plan B. For some reason, the n800 mounts the corrupt filesystem. Plan B is to copy as much as possible from the card to backup, reformat, and restore. Fortunately, the little files (text, etc.) are the important ones. The big files - audio and video, are never edited on the n800, and so are available on the desktop, if i want them. In fact, a list of directories is enough to restore these. The first attempt at backup failed. There's a directory loop, and the backup keeps cycling through the same files... But it appears that most or all the files will be recoverable. Last week's backup will not be needed. A good thing, since lots has happened in the last week.

No idea what might have caused the error.

My friends complain that it is impossible to mess up a flash drive.