What is the best way to upgrade OS?

[qox]

The appliance version is 5.3.
The master server OS reads Red Hat Enterprise Linux release 8.6 (Ootpa) and also Oracle Linux Server release 8.6.
The Veritas NetBackup application version is 10.3.0.1.

According to the first table (NetBackup Appliance) on this page, I am supposed to upgrade to RHEL 8.8.

What is the best way I can perform this job? And will the Veritas NetBackup application get affected?

[StefanosM]

first of all, you can not upgrade the OS of an appliance yourself. You can not even install any software unless instructed by support.

According the table you provide, your appliance, that is at 5.3, is running RedHat 8.8.

you can check it by running the flowing command at maintenance mode
cat /etc/os-release

[kiyan]

As @StefanosM , you can find out the details about your appliance, by logging into CLISH (ssh to appliance), and accessing the OS level , if you do not know how , refer to below link:
https://www.veritas.com/support/en_US/doc/96220900-127024912-0/v113564108-127024912

once you are in the the CLI and you have entered the "elevate"
#cat /etc/vxos-release     (it will give you details about vxos)
#cat /etc/nbapp-release   (it will give details about netbackup version and platform)

[qox]

I said the master server, which is RHEL, needs to be upgraded to 8.8 (first screenshot in my post). I didn't say that the appliance is the one that needs the upgrade.

@kiyan, the second screenshot that I posted above is from the appliance, and it shows the version of it. I got it from Appliance > Status.

Now by running the commands you suggested, we've got the same result, haven't we?

[kiyan]

yes,we got the same result, but now it is clear what you want!
for RHEL and Oracle, you can do in place upgrade or you can install a fresh OS and do the DR on top of it. just take a backup of your catalog (and have it offline with you) before you do any activity, just in case it did not go smoothly.
always confirm the compatibility before you do any upgrade for OS and netbackup:(software compatibility)
https://www.veritas.com/support/en_US/article.100040093

[bhdrkzltn · Accepted solution]

"According to the first table (NetBackup Appliance) on this page, I am supposed to upgrade to RHEL 8.8."
You don't have to upgrade your master server OS version as its version is irrelevant with the OS version used by appliance.
It's always good practice to keep your OS up-to-date wrt security concerns then just run "yum update" on your master server. NetBackup 10.3.0.1 is fully compatible with RHEL 8.x and even 9.x.

[qox]

Just now I realised that the 8.8 in the table is of the appliance itself, not the master server. And my appliance is already 8.8. So it will go till next year. But I'll try to upgraded the master for security purposes.