Oracle certifies many of their latest products for installation on Oracle Linux 6 and 7, so I guess the obvious question is, which should you pick?
I tend to have a dual approach to this. I always use the latest versions of everything for my play kit, but I tend to be a little conservative for production deployments, preferring to use the OS version the product was developed against. I’ve noticed Oracle Cloud and some VM templates are still using Oracle Linux 6, which makes me think Oracle are being a little conservative too.
We were lucky enough to get some time with Wim Coekaerts during the ACE Director briefing at Oracle OpenWorld 2015. During Wim’s session I asked this very question and (to paraphrase his response) he said, the products are written on Oracle Linux 6, so that’s a safe bet. The products are certified and supported on Oracle Linux 7, so you are fine to choose that, but it doesn’t really matter if you prefer to stick with Oracle Linux 6.
You might be asking yourself, why would I stick with such an old distribution? If you are using Oracle Linux you should be using Oracle’s kernel (currently UEK3), so even if the main distribution is older, you are still getting the latest and greatest kernel updates. This is very different to RHEL, where the kernel functionality is essentially fixed when the distribution is released, then just patched for critical updates. For a database or application server, the kernel is the important thing. You’re not bothered about having the latest version of Firefox on the server.
Oracle Linux 6 is supported until 2021, so there is no hurry to get rid of it any time soon. If you are doing new installations, the likelihood is your hardware replacement cycle will kick in before Oracle Linux 6 is out of date. If virtualized, you will probably rebuild your VMs as part of your application software updates within this time-scale also.
So in conclusion, don’t be afraid to make the jump to Oracle Linux 7, but equally, don’t be afraid to stick with Oracle Linux 6… Neither choice is a bad one in this case.
PS. For non-Oracle installations, there may be other more pressing reasons to jump to version 7. I’ve intentionally avoided mentioning systemd and firewalld. I don’t have time for that war.