[ale] Clone live system?

[DJ-Pfulio]

On 7/17/21 9:53 AM, Raj Wurttemberg via Ale wrote:
> 
> Now that COVID is slowly going away, some of our customers are now
> looking to do some OS upgrades, mostly RHEL 6 to RHEL 8 and SuSE 12
> to SuSE 15.  We have been using Relax and Recover (ReaR)
> (https://access.redhat.com/solutions/2115051
> <https://access.redhat.com/solutions/2115051>) which dumps the live
> system to a bootable ISO. No outage is required.
> 
> We take the ISO, boot it on a temp server, upgrade the OS there and
> on upgrade day, reverse the process on the day that we get an outage
> from the customer. The ReaR process works ok, but if any of the file
> systems are separated like /usr, or, /var, etc...  like you would
> normally find on a system, ReaR runs into difficulties.
> 
> I did some Google-ing for other tools that can create a live clone of
> a server. I did find two tools that look promising...
> 
> - doClone : http://doclone.nongnu.org/ <http://doclone.nongnu.org/> -
> MondoRescue : http://www.mondorescue.org/
> <http://www.mondorescue.org/>
> 
> Besides 'dd' I was curious what live cloning software you all have
> tried.

Take an LVM snapshot and use fsarchiver on the snapshot.  Of course, if you don't have snapshot capable storage already, there isn't much that can be done.

The days of splitting off /usr have long ended. Heck, for lots of systems even /var/ doesn't need to be a separate FS. It isn't like our total storage is 200MB and log file sizes can't be limited.  

A quick analysis of the storage layout should easily tell an admin if they need multiple LVs for different storage areas.
Handy: lsblk -e 7 -o name,size,type,fstype,mountpoint'

Add in the uuid column, if you mount using those. 
I prefer using the /dev/{vg-name}/{lv-name} mount device links.