docs: Clarify NFS version requirements for Longhorn features

[sushant-suse]

Which issue(s) this PR fixes:

Issue- JIRA: 9609

What this PR does / why we need it:

It updates the documentation (for installation in 1.9.x, 1.8.x, 1.7.x and 1.6.x.) to clarify the NFS version checks for Longhorn functionalities. It adds a clarification regarding the required NFS versions (NFSv4, NFSv4.1, and NFSv4.2) for Backup/Restore and ReadWriteMany (RWX) volumes.

Special notes for your reviewer:

The changes are primarily documentation updates, and there are no code modifications.

Additional documentation or context

No

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[jillian-maroket]

The info you added already exists in the doc. Check my comment.

[jillian-maroket]

Line 204 contains the same information. How does the new content address the customer's pain points?

[sushant-suse]

The info you added already exists in the doc. Check my comment.

The customer's pain point was that the documentation only checked for kernel support for NFSv4, v4.1, and v4.2, but didn't guide on active NFS version being used by the system. Simply having kernel support doesn't guarantee the correct version is in use, which could lead to issues with Longhorn's backup/restore and RWX volume features.

Line 204 mentions the NFS version requirements for Longhorn and the need for kernel support, it does not tells above the active NFS version on their system.
This addition clarifies that the kernel support checks are a prerequisite, but the active NFS version is what matters for Longhorn functionality.

I asked Derek, and he suggested that we should not change the original doc, rather mention in a few sentences

For longhorn, some functionalities use NFS
backup/restore: use NFS4.2, NFS4.1 or NFS4.0.
rwx volume: use NFS4.1

[jillian-maroket]

@sushant-suse @derekbit Part of our job is to ensure that users are not forced to read unnecessarily lengthy documentation. Why add a block of text within the same section if we can reorganize the existing content to accommodate new information?

This is not my task so you can make the final call. Just letting you know that this is how I would respond to the customer's feedback.

Some Longhorn features require specific NFS versions to function correctly. Before installing the NFSv4 client userspace daemon and utilities, verify that your kernel supports one of the following NFS versions:

• Backup/Restore functionality: NFSv4.0, NFSv4.1, or NFSv4.2
• ReadWriteMany (RWX) volumes: NFSv4.1

You can check if the kernel supports the listed NFS versions by running the following commands:

• NFSv4.1: cat /boot/config-uname -r| grep CONFIG_NFS_V4_1
• NFSv4.2: cat /boot/config-uname -r| grep CONFIG_NFS_V4_2

Important: You must also verify that the required NFS versions are in use.

[derekbit]

@sushant-suse @derekbit Part of our job is to ensure that users are not forced to read unnecessarily lengthy documentation. Why add a block of text within the same section if we can reorganize the existing content to accommodate new information?

This is not my task so you can make the final call. Just letting you know that this is how I would respond to the customer's feedback.

Some Longhorn features require specific NFS versions to function correctly. Before installing the NFSv4 client userspace daemon and utilities, verify that your kernel supports one of the following NFS versions:

• Backup/Restore functionality: NFSv4.0, NFSv4.1, or NFSv4.2
• ReadWriteMany (RWX) volumes: NFSv4.1

You can check if the kernel supports the listed NFS versions by running the following commands:

• NFSv4.1: cat /boot/config-uname -r| grep CONFIG_NFS_V4_1
• NFSv4.2: cat /boot/config-uname -r| grep CONFIG_NFS_V4_2

Important: You must also verify that the required NFS versions are in use.

Sounds good. @sushant-suse Can you respond to the jira ticket and check the report's response?