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If we have a partition /dev/sda1, and mount it to a mount point (i.e. /mnt), we can then use the files and folders under /mnt. Before changing the partition /dev/sda1 I umount /mnt, and then perform disk resizing operations.

When/mnt has been unmounted I am confused as to how 'data corruption' can occur because the filesystem (/mnt) has been unmounted.

i.e. after sometimes resizing the disk I get errors after I run e2fsck on the unmounted partition - does this mean the actual data is stored on the partition /dev/sda1 or is it meta-data of some sort?

Also in the future if I wish to make a backup would it make more sense to use dd to backup the partition or use cp to copy the data under /mnt?

fsck /dev/sda2
fsck from util-linux 2.20.1
e2fsck 1.42.5 (29-Jul-2012)
fsck.ext3: Group descriptors look bad... trying backup blocks...
fsck.ext3: Bad magic number in super-block while trying to open /dev/sda2

The superblock could not be read or does not describe a correct ext3
filesystem. If the device is valid and it really contains an ext3
filesystem (and not swap or ufs or something else), then the superblock
is corrupt, and you might try running e2fsck with an alternate superblock:

e2fsck -b 8193 <device>

Thanks.

  • dd works low level, So When you want to resize partition or change its block address, dd is wrost options.Use a command such as tar or cp or so on.Try to mount looply your dd file. – PersianGulf Apr 18 '15 at 11:28
  • I don't get what you mean “does this mean …”, also can you show us the errors from e2fsck. – ctrl-alt-delor Apr 18 '15 at 12:02
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    @ams; with respect to backups; I don't think dd makes sense for anything else than raw backups (no individual access or restoration), and cp makes only sense for small and isolated data. You probably want something more sophisticated. There are a couple options; you may want to have a look into rsnapshot, for example. – Janis Apr 18 '15 at 15:49
  • @MohsenPahlevanzadeh why would I use a loop device? I'm guessing that's what "mount looply" means. Also a filesystem cannot be mounted to a /dev/loopX device can it? – user Apr 18 '15 at 23:16
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    @ams, looply for ccpy your old data. – PersianGulf Apr 19 '15 at 12:21

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