[CentOS] bare-metal backup before update--options?

[Simon Matter]

> Hi all!
>
> I'm a "nervous nellie", I have not yet updated my 7.5 desktop to 7.6
> because (1) it has an Nvidia card, and (2) I've heard of problems
> upgrading on top of software RAID (using RAID1 with 2 drives).
>
> I need to upgrade it to stay secure, and I want to do a bare-metal backup
> first (so I can put it all back as it now is, in case it explodes in my
> face), so I'm trying to figure out the safest way to do that. Here are
> the choices as I see them, I'd appreciate comments/thoughts:
>
> 1. boot from live DVD and manually reassemble the RAID array (how
> would I do that?)
> 2. degrade the array (with appropriate commands) so that it is running
> on just one drive, then boot a live DVD and use dd to back up that drive.
> 3. Other choices you can suggest?
>
> then after successfully getting a bare-metal backup, reboot it with the
> full RAID array and run the update.
>
> Thanks in advance!

To me the easiest method seems to:

- boot into rescue mode, not mounting any disks
- directly dd all complete disks to files on a USB disk or to a remote host
- reboot and update as usual

If anything fails you can again boot into rescue mode (maybe with the help
of USB/DVD/CD) and:

- recover all disks using dd from the backups made before
- reboot and be back on 7.5

Any reason why this shouldn't work?

Regards,
Simon