Clarify rear mkbackup vs rear mkrescue

[tahliar]

PR creator: Description

rear mkbackup is only used with the internal backup tool, not with third-party backup tools. These are used separately, in combination with rear mkrescue.

PR creator: Are there any relevant issues/feature requests?

• bsc#1218910
• jsc#DOCTEAM-1243

PR creator: Which product versions do the changes apply to?

When opening a PR, check all versions of the documentation that your PR applies to.

• SLE-HA 15
  • 15 next (current main, no backport necessary)
  • 15 SP5
  • 15 SP4
  • 15 SP3
  • 15 SP2
  • 15 SP1
• SLE-HA 12
  • 12 SP5
  • 12 SP4

PR reviewer only: Have all backports been applied?

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When opening a PR, do not set the following check box.

• all necessary backports are done

[tahliar]

Original overview: https://documentation.suse.com/sle-ha/15-SP5/html/SLE-HA-all/cha-ha-rear.html#sec-ha-rear-concept-overview

New overview:

Original procedure: https://documentation.suse.com/sle-ha/15-SP5/html/SLE-HA-all/cha-ha-rear.html#sec-ha-rear-mkbackup

New procedure:

[jsmeix]

@tahliar
if you like, you may emphasize in the second "EXAMLE 27.4"
that "rear mkrescue" does the same as "rear mkbackup"
except making the backup of the files,
i.e. "rear mkrescue" analyzes the system and creates
the ReaR recovery system same as "rear mkbackup" does.

FYI:
There is also "rear mkbackuponly" which only
makes a backup with ReaR's internal 'tar' backup method
but it does not do the "rear mkrescue" part.
So in the end there are two separated basic things
"rear mkrescue" versus "rear mkbackuponly"
and "rear mkbackup" does both sequentially
i.e. "rear mkrescue" followed by "rear mkbackuponly"
so calling

# rear mkrescue
# rear mkbackuponly

results the same as calling

# rear mkbackup

when ReaR's internal 'tar' backup method is used.

[dariavladykina]

LGTM.