Saturday, September 8, 2012

Keeping your old installation files at hand

So long Fedora, welcome Mint. I Managed to dump my entire hard drive to a file with dd so I can start my "old" installation in a kvm virtual machine: I also made a qcow2 delta disk of the base image that I can mount with nbd so I can browse my files easily.

The dump was done with dd directly to a file on a USB Hard drive, it took several hours, but the procedure is as simple as this:
dd if=/dev/hda of=/media/SAMSUNG-tera bs=1048576
I always specify the block-size in dd since the default is too low and has much overhead.

 This "dump" is, qemu-wise, a virtual disk image of tipe "raw", and as such is usable to run a VM. But I don't want this image to change since I still want to be able to restore it if I change my mind about the reinstallation, so I set it to read-only and I created two delta-disks over the raw file that I can access r/w to power the vm on and to browse the files with qemu-img:

qemu-img create -f qcow2 -o backing_file=poldon-180812-base.img,backing_fmt=raw writable-poldon-0001.qcow2
I run the VM from the qcow2's so I can keep the dump as it was at the beginning and eventually dump it back to my HD, while I can make all the modifications I want to the qcows to adapt the OS to the virtual hardware.

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