I realised recently I've been using Linux for about 25 years (anyone else remember the InfoMagic CD sets which had basically ALL the available distros in one 6-CD box for like $20?) and although I'm pretty handy with it there's certainly areas I could brush up on, and I don't have any bits of paper to prove I know anything at all.. So, my thoughts have turned to Linux Certification. I see there's LPIC, CompTIA Linux+, RHCSA, etc. Anyone done any of them, or are any more credible than any others, etc? Lately I've been using Centos for home stuff and Amazon Linux 2 for cloud stuff but I've used pretty much every major server-oriented distro over the years. Is there a best distro to focus on?