Ubuntu – How to Verify/Restore Whole-System Backup of tar czf

I want to test that the whole system backup corresponds to the original.
It would be great to understand some basic tests about rapid quality assurance because I do not have time to always .untar it completely.
Do backup backup.tar.gz of the system with exclusions

# http://unix.stackexchange.com/a/291720/16920
sudo nice tar czf /media/masi/ntfsDisc/backup.tar.gz --exclude=/home \
    --exclude=/media --exclude=/dev \
    --exclude=/mnt --exclude=/sys \
    --exclude=/run --exclude=/proc /

Tests by Case Studies

1. How to Handle cases of changed files during the backup?

   tar: Removing leading `/' from member names
   tar: /home/masi/.gnupg/S.gpg-agent: socket ignored
   tar: /home/masi/.config/chromium/Default: file changed as we read it
   tar: /home/masi/.config/chromium: file changed as we read it
   tar: /home/masi: file changed as we read it
   

2. How to handle ignored sockets?

   tar: Removing leading `/' from member names
   tar: /tmp/.X11-unix/X0: socket ignored
   tar: /tmp/.ICE-unix/1666: socket ignored
   tar: /tmp/qtsingleapplication-7af9-3e8: socket ignored
   tar: /tmp/.org.chromium.Chromium.2qSs7o/SingletonSocket: socket ignored
   

Methods to tests

1. Take a md5-map of directories. Compare it to the current system. It should not have changed much.
2. If md5 has changed more than the significance factor
   • Some specific searches of the contents in the directory, which should be enough vertical to each other to satisfy the system testing.
3. Aim: real-time quality-assurance. To distribute computing and balance between power and time-duration so nice. TODO timing of the process and sub-processes.

Test requirements

• Permissions/owners unchanged between backup and local files.

System: Ubuntu 16.04
Filesystem of System: ext4
Filesystem of external HD: NTFS