Bug 1465182

We offer the --online-backup flag in 6.2 but there needs to be a warning statement when running with this flag as there is a caveat with its use.

Satellite 6 uses two database systems, Postgres and Mongo. There are records that exist in Postgres and Mongo that need to remain consistent and in sync between each system. 

When you shut down all the services you can ensure that there are no modifications occurring to either database. The --online-backup flag keeps all services running so there is a possibility that exists that data being modified while the backups are occurring. There is a basic check in place in the backup routine that checks to see if the database was modified during the backup. If this occurs, it will re-backup the data and start over. 

This check is rudimentary and can't ensure with 100% certainty that there were no modifications to the Pulp or Postgres database while the backup was running. This check can also result in repeated loops if there is continuous modification occurring to the database. If the user still wishes to use the --online-backup flag for production use they will need to ensure that there are no modifications that occur during the backup runs. 

We need to add a warning that explains this, for example (the wording is open for discussion):

# katello-backup /var/tmp --online-backup

*** WARNING: The online backup flag is intended for making a copy of the data
*** for debugging purposes only. The backup routine can not ensure 100% consistency while the 
*** backup is taking place as there is a chance there may be data mismatch between 
*** Mongo and Postgres databases while the services are live. If you wish to utilize the --online-backup
*** flag for production use you need to ensure that there are no modifications occurring during 
*** your backup run. 

Satellite 6.3 will offer LVM based snapshots for 'hot backup' function and we can then remove this warning.