Add Rocky Linux installation example

[berlin2123]

Install example for Rocky Linux 9 (Not Released) or Centos Stream 9 (Tested).

copy from example_centos.rst

[CarlSchwan]

I'm not sure it's a good idea to have a rocky Linux documentation page and I would prefer to have one page for rhel/rocky/almalinux page and maybe another one for centos stream (if needed). This will be less work to maintain long term

[berlin2123]

rhel9/centosstream9/rocky9/almalinux9 can use the same document.

[tflidd]

Wouldn't it be better to update the CentOS version and keep this updated. You can then mention that it was tested with other distributions as well.

I think it will be too much to ask to keep manuals for too many Linux distributions up to date. If there is some experience that isn't documented in the official documentation, you can also post in the howto section of the forum help.nextcloud.com

[berlin2123]

Why not using the CentOS stream 9 ?
1,The downstream version of RHEL, CentOS, which has more than 10 years of update support, is in '/dev/null' now. The upstream version, CentOS stream, has only 5 years of update support.
2, The software version of CentOS stream is too new, which may has more bugs.
Choosing other downstream distributions of RHEL, may make the system run more stable, and get longer update support.

Why not just update 'example_centos.rst' ?
The old 'example_centos.rst' is suitable for RHEL8/RockyLinux8.
When using RHEL9/RockyLinux9/Almalinux9, there is no CentOS anymore. CentOS Stream 9 is not that stable for NextCloud.
So, at the RHEL9 epoch, we may have to move to 'example_rockylinux.rst', and then delete 'example_centos.rst'.

Why choosing Rocky?
It is the only one Not from any commercial company, which may have longer live time, and avoid for going to Null as CentOS did.

Merging this now?
The stable RHEL9 is Not Released yet, so the same for the downstream RockyLinux9. We may merge this after the release of RHEL9.