You are in way over your head

Stop now before you get yourself in hot water

Is there an application that allows easily sharing files on one Linux system? That would be nice!

this sentence made me remember this: https://github.com/9001/copyparty

.. don't they? usually, owner of the directory can change its permissions, and ACLs when those are enabled for the mount

Your job as sysadmin is to adhere to your organization's policy, no matter how stupid and hindering that policy might seem to you.

You're knowingly giving your users a workaround to their NDA, which puts all of your jobs and your data confidentiality at risk.

You've got no business with root privileges.

If you're not that worried about storage then you can just make copies if necessary, then you don't really have to worry about permissions (apart from read, which is typically default for the same group). But yea if there's any chance more than 1 person might work off the same copy of data on HPC, make it read only for the peace of mind. Regarding conda envs, yea I have a few common read only conda environments so that scripts can be used by multiple users without the hassle of ensuring everyone has the same env. Quite useful.

Changing permissions is not the same as bypassing permissions

Fuck off.

Not what I need, but it looks very cool!

I have no root privileges, I'm providing no NDA workaround.

The shared environment thing seems like a very cool idea! I'll try to set it up.

Not strictly about compliance, setting up FTP or WebDAV is technically complex without root access. You'd have to account for the fact that sessions on a HPC are time limited.
Probably you can come up with some workaround that way, but I'm not sure that is any better than my current setup.

You could use Copyparty. No root needed.

I didn't fully understand what this software does, but it looks pretty neat.
However, regardless of what it does, this is not something that I could use in my case.
This spawns a server and I imagine it can do it's thing only as long as the server is running. Which in my case it would be around 8 hours which is the login session time limit on the HPC.
Moreover, I'd be running a potentially resource hungry process on a login server, which is a big problem. I could request a compute job and run this there I guess, but this would still be limited by the queue max time.
Moreover, while not impossible, the login node to login node communication would be a pain in the ass.
I'd have to either always connect to the same node to spawn it or to let everyone know of the IP the server is currently running on. And I'd have to do this manually every 8 hours.
It is feasible, but this is probably a better software for other kinds of problems.

Previously you said you didn't want to duplicate the files because it was a ton of data. Now you're saying that accessing it on demand is impractical.

It's becoming difficult to help you. Not because of your technical context, but your attitude.

Copyparty introduction

I'm grateful for all the help and advice in here. Duplicating the data is not a problem, we can have several copies of the data on the server, not an issue.

Having the data on an external server on the other hand may be a problem, because that would require quite a large amount of storing capacity.

I'm unsure what you mean by accessing on demand: data already is on the server and people can access it. My main pain point is that if people copy stuff in there rather than creating it in place I do not get write access by default.

The copy party software looks interesting for other applications, and I may pick it up for something else, but it is not something that would work in this case.
As I have explained extensively, while spawning a file server would not be impossible, it would be a huge hassle with no real advantages.

Hello, I'm back after trying. The g+s permission does not change group permissions when copying a file.
However, I have observed that I can delete copied files even though those are 630 and supposedly I should not be able to modify them.
That is good enough for me: as long as I can delete the stuff it's ok, if I need to modify I can always copy it somewhere else.