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backups for SD card disk image? that don't take up tonnes of space and can be rolled back? (lemmy.world)

submitted 1 month ago by [email protected] to c/[email protected]

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I would like to make manual backups of an SD card as a disk image so that it can be easily recreated when needed. I'd like to keep a few versions in case there is a problem I didn't know about, it can be rolled back.

How can I do this incrementally, or with de-duplication, so that I don't have to keep full copies of the complete SD card? It's very big but most of the content won't be changing much.

It's for MiyooCFW ROM which is on FAT 32-formatted micro SD card.

Thanks for your help! Also let me know if I am going about the problem in a wrong way.

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[–] [email protected] 2 points 1 month ago (1 children)

I'm not sure about anything that does rolling backups of full disks, but I have used rdiff-backup for years for rolling backups of individual files. The format for the backup is similar to (and based on) rsync so it's fairly easy to script. For complete servers I just keep a copy of the install image on hand, in a catastrophic drive failure I can do a new installation to a new drive (creating the partitions, grub setup, etc), then restore the latest backup. An alternative might be to use dd and create a full drive image file to use as your starting point in a full recovery.

One thing to keep in mind though is that the backups should NOT contain any system folders like dev or proc that get generated at boot. If possible, when making a starting image with dd, you want the drive to be separate and not part of the running OS, because some folders like dev and var have a basic set of files in place needed for the boot process which may be different than the final version you see after the OS is up and running. That's why I find it easier to just plan around a clean install to new drives when needed.

[–] [email protected] 1 points 1 month ago

Thanks I will look at rdiff. I am not sure if rsync is able to "see inside" the *.img files to discern the individual files. If it can then it would be helpful because I could just re-write the same file over and over again and keep backups using rsync or any of the various rsync-derrived tools?

The filesystem will be cold at time of back up because I will need to shut it down, remove the card from the console and put it into my computer's reader so no worries about that.