tmpfs/ramdrive -> test -e /etc/rear-release

[ProBackup-nl]

Doc seems to incorrectly state that the code would check for running from tmpfs or ramdisk. The actual check in code that I can find is much simpler: "test -e /etc/rear-release" at https://github.com/rear/rear/blob/master/usr/sbin/rear
Better reflect the actual behavior in documentation.

[jsmeix]

@schlomo @gdha
in
https://github.com/rear/rear/blob/master/doc/user-guide/09-design-concepts.adoc
I don't know what the "demo" recovery workflow should be and/or
how a "demo" recovery workflow could be started manually.

According to the code in
init/default/050_check_rear_recover_mode.sh
any "rear recover" command would be aborted
unless /etc/rear-release exists.

The part about the "demo" recovery workflow in
doc/user-guide/09-design-concepts.adoc
exists since that file had been created as
doc/relax-recover-concept.txt
on Jun 14 2011 via
f4fae8a

[jsmeix]

I think the whole paragraph

The recovery workflow is triggered by the fact that
the root filesystem is mounted in a ram disk or tmpfs.
Alternatively a "demo" recovery workflow can be
started manually. This will simply recover all data into
a subdirectory and not touch the hard disks (Phase 2).

might be deleted because /etc/rear-release is an implementation detail
that does not need to be documented here and I guess that "Phase 2"
means that the "demo" recovery workflow was meant to be
implemented in the future but it never happened.

[schlomo]

I am not aware of a demo recovery workflow and git grep doesn't find anything. So probably a good idea to remove this part of the documentation till somebody implements such a workflow.