Rear backup returns 0 (successful) status but output indicates failure

Issue

• When running rear, it completes successfully but we can see some errors regarding the backup creation:

Creating recovery/rescue system initramfs/initrd initrd.cgz with gzip
default compression
Created initrd.cgz with gzip default compression (209575340 bytes) in 23
seconds
Creating tar archive
'/tmp/rear.zljYzEfrfrGREGTLMZSM/tmp/isofs/osbackup/linux/backup.tar.gz'
Archived 2567 MiB [avg 12572 KiB/sec] OK
WARNING: tar ended with return code 1 and below output:
  ---snip---
  tar: /var/spool/postfix/public/qmgr: socket ignored
  tar: /var/lib/gssproxy/default.sock: socket ignored
  tar: /spec/opensso_config/opensso/stats/intLocalStats: file changed as we
read it
  ----------
This means that files have been modified during the archiving
process. As a result the backup may not be completely consistent
or may not be a perfect copy of the system. Relax-and-Recover
will continue, however it is highly advisable to verify the
backup in order to be sure to safely recover this system.

Archived 2377 MiB in 213 seconds [avg 12781  KiB/sec]
Making ISO image