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problem with compressed image

Posted: Thu Mar 13, 2014 4:44 pm
by dandnsmith
I'm using version 1.61 of the tool to save RaspBMC images under Win7 from 8GB SD Cards as backups.
I've successfully saved uncompressed images and restored them to other cards (using Device mode, because of having 2 filesystems on each card, one FAT the other EXT4)
In order to save space I've done a couple of backups with compression to .img.gz, which reduces the image from 8GB to less than 2GB.
When I restored from one of these to a different, already used, card (same manufacturer, same size), I noticed that the restore clocked up over 189% - which, itself, didn't put me off. However, when booting from the restored image things went wrong, and I got a message which said that filesystem size was 1946880 blocks according to the superblock, but the device size was 1921536, and this was followed by an apparently unending stream of error messages.
The card which was backed up was somewhat damaged - so have I done something wrong, or was the damage to blame, would you guess?

Re: problem with compressed image

Posted: Thu Mar 13, 2014 8:17 pm
by Alex
1) The 189% comes from the gz file format only being able to store up to 4GB. The calculation can be wrong with larger images.

2) Did you restore the image to a smaller SD card using the truncate option? At least the error message sounds like that.

Re: problem with compressed image

Posted: Fri Mar 14, 2014 1:06 pm
by dandnsmith
Thanks for that.
The cards were hama 8GB sd cards, which were bought at about the same time.
I didn't use any truncate option.
I have, meantime, restored another (uncompressed) image to the damaged card, and it promptly fell flat on its face after booting - which strongly suggests I throw it away as unusable