After having a corrupted file system on my SD card due (probably due to unsufficient power supply) I want to make a new filesystem. (e2fsck fails, log below.)
However, any file-related changes on the SD card are magically undone!
- First example: when I mount the SD card, delete some files, the files disappear. When I unmount it and mount it again, the files are there again! Similarly when I modify a file's content, the original content is back after re-mount.
- Second example: when I create a new partition table with
fdisk, the old partition table is back in place immediately. (Log below.) - Third example: while I run
dd if=/dev/zero of=/dev/mmcblk0 bs=1M,fdiskreasonably saidDisk /dev/mmcblk0 doesn't contain a valid partition table. Whenddwas done, the old partition table was back again.
I have not locked the SD card physically with the small switch. I don't get any read-only errors. In fact, I don't get any errors at all! dmesg doesn't report anything except that I'm mounting a file system with errors.
The problem also occurred running a Xubuntu live cd (12.10). Unfortunately I don't have access to other computers and/or SD card readers at the moment.
Is that a problem of my computer, my SD card, or am I missing something all the time? Any suggestions what I could try?
e2fsck fails:
$ sudo e2fsck /dev/mmcblk0p2
e2fsck 1.42.5 (29-Jul-2012)
/dev/mmcblk0p2: recovering journal
Superblock needs_recovery flag is clear, but journal has data.
Run journal anyway<y>? yes
e2fsck: unable to set superblock flags on /dev/mmcblk0p2
/dev/mmcblk0p2: ********** WARNING: Filesystem still has errors **********
Here's the log that shows that fdisk has no effect:
$ sudo fdisk /dev/mmcblk0
Command (m for help): p
Disk /dev/mmcblk0: 31.5 GB, 31460425728 bytes
4 heads, 16 sectors/track, 960096 cylinders, total 61446144 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00017b69
Device Boot Start End Blocks Id System
/dev/mmcblk0p1 8192 122879 57344 c W95 FAT32 (LBA)
/dev/mmcblk0p2 122880 61446143 30661632 83 Linux
Command (m for help): d
Partition number (1-4): 1
Command (m for help): d
Selected partition 2
Command (m for help): p
Disk /dev/mmcblk0: 31.5 GB, 31460425728 bytes
4 heads, 16 sectors/track, 960096 cylinders, total 61446144 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00017b69
Device Boot Start End Blocks Id System
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
Syncing disks.
$ sudo fdisk -l /dev/mmcblk0
Disk /dev/mmcblk0: 31.5 GB, 31460425728 bytes
4 heads, 16 sectors/track, 960096 cylinders, total 61446144 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00017b69
Device Boot Start End Blocks Id System
/dev/mmcblk0p1 8192 122879 57344 c W95 FAT32 (LBA)
/dev/mmcblk0p2 122880 61446143 30661632 83 Linux
Best Answer
At this point I would suggest running badblocks on the SD card to see what it finds.
It sounds like the card's write logic is damaged, what you see on a mount point is simply the cached version of your data. It's supposed to be written back via sync and during umount. Seeing that you don't mention that the SD card is hanging at all suggests the damage is severe enough to create false positive write back responses or in simpler terms your disk is lying to you when it says a write is complete.
You could try toggling the write protect switch while the card is removed from the system. e.g.
In an effort to tickle the circuitry which might be caching a "stuck at 1" value. Other than that, crush it so no one else suffers any more grief and toss it.