[CentOS] imaging a drive with dd

[Warren Young]

On Mar 2, 2017, at 6:36 PM, Robert Moskowitz <rgm at htt-consult.com> wrote:
> 
> I want to image the drive at various 'checkpoints' so I can go back and redo from a particular point…
> what dd params work?
> 
> dd if=/dev/sdb of=os.img bs=1M count=3210

That looks plausible.  (I haven’t verified your count parameter exactly.)

However, I wonder why you’re trying to reinvent snapshots, a technology now built into several advanced filesystems, such as btrfs and ZFS?

    https://en.wikipedia.org/wiki/Btrfs#Subvolumes_and_snapshots

btrfs is built into CentOS 7.  While there have been some highly-publicized bugs in btrfs, they only affect the RAID-5/6 features.  You don’t need that here, so you should be fine with btrfs.

And if you really distrust btrfs, ZFS is easy enough to integrate into CentOS on-site.

And if *that* is also out of the question, you have LVM2 snapshots:

    http://tldp.org/HOWTO/LVM-HOWTO/snapshots_backup.html

Why reinvent the wheel?