No I don't believe any shared hosting does this (at least not ones anybody pays money for). Dreamhost and Nearly Free Speech definitely don't.
This might have been true 20 years ago, but I doubt it was true 10 years ago, and definitely not today. Maybe some tiny universities had janky setups like this.
Fun fact: shared hosting providers maintained OS virtualization for Linux years before Docker existed.
I'm not quite sure but it also appears to have pre-dated cgroups. If you pack many users together on a server, you will want something like cgroups to prevent neighbors from DOS-ing each other.
This was a fork and wasn't in mainline Linux.
So they actually had MORE isolation than running as separate Unix users, not LESS.
(edit: I'm not sure exactly which shared hosting providers used such Linux kernel forks, but I'd be interested in anyone with direct knowledge. From using the shell on various shared hosting providers, I know they have pretty custom configurations with more isolation than stock distros.)
Nope, most shared hosting is still like the OP comment’s description.
Then of course you have companies like Cloudflare and Netlify where their shared static hosting is not the traditional lamp/cpanel stuff, and certainly have internally developed platforms/serving technologies where security and sandboxing is very likely top of mind.
Companies of Cloudflare and Netlify ilk are the exception, but most cheapo shared hosting (and shared hosting has to be cheap to compete), is still very much multi-tenant with security concerns across the board.
I've used 3 shared hosting providers, all of which provide SSH access. And when I ssh in, and type "ps", I see my own processes, not the processes of anybody else. They are running as a different user.
You can have unique SSH users and still have all the PHP code run under a shared user on the web server. The machine you SSH in is most likely not the same as the one running your PHP code even.
This might have been true 20 years ago, but I doubt it was true 10 years ago, and definitely not today. Maybe some tiny universities had janky setups like this.
Fun fact: shared hosting providers maintained OS virtualization for Linux years before Docker existed.
https://en.wikipedia.org/wiki/OpenVZ -- initial release 2005
I'm not quite sure but it also appears to have pre-dated cgroups. If you pack many users together on a server, you will want something like cgroups to prevent neighbors from DOS-ing each other.
This was a fork and wasn't in mainline Linux.
So they actually had MORE isolation than running as separate Unix users, not LESS.
(edit: I'm not sure exactly which shared hosting providers used such Linux kernel forks, but I'd be interested in anyone with direct knowledge. From using the shell on various shared hosting providers, I know they have pretty custom configurations with more isolation than stock distros.)
This page is a little fuzzy: https://en.wikipedia.org/wiki/Virtuozzo_(company)