Re: RHEL OS upgrade from 6.7 (Current version) to 8 version for Postgresql database

On a side note, shouldn't you be upgrading to CentOS Stream instead of 
CentOS 8?

Tom Lane wrote on 3/19/2021 10:19 AM:
> ram pratap maurya <rampratap0000@gmail.com> writes:
>> we are planing to RHEL OS upgrade from 6.7 (Current version)  to 8 version.
>> currently postgresql-12.6 version running on the server ,  we have upgraded
>> OS on test DB server from 6 to 8 version  during  OS upgrade
>> postgresql-12,11 and other package is removed  and Postgresql is not
>> started. that why my DB is crashed , can you please suggest what is best
>> way to upgrade OS.
> There are a couple of big gotchas you need to think about:
>
> * RHEL8 is systemd based, while 6 still used the old initscript startup
> code.  This means that the way to get a daemon process launched is
> completely different.  So PG packages built for RHEL6 *will not work*.
> You need to get a server package that is systemd-ready, and that means
> one that was explicitly built for RHEL8.  (Maybe a RHEL7 one would
> work, not sure.  But it is zero surprise that the packages you listed
> aren't working.)
>
> * RHEL8 incorporates new locale data [1].  This means that non-English
> text is rather likely to sort differently than it did before, which in
> turn means that indexes on text columns will be corrupt if you try to
> upgrade in place.  While you could REINDEX them after updating, this
> might be a good reason to do a dump-and-reload instead of trying to
> pg_upgrade.
>
> In short, this is no minor upgrade you're contemplating.
>
>             regards, tom lane
>
> [1] https://wiki.postgresql.org/wiki/Locale_data_changes
>
>