rlimits

You have standard rlimits, but also ambiguous ones like LowPriorityIO and LimitLoad<wildcard>, latter ones depending on sysctl variables.

If you're running qmail processes without data size rlimits, you're vulnerable to resource-exhaustion denial-of-service attacks in any case.

We already have other accounting mechanisms for processes/threads (rlimits) and for inodes and disk space (disk quota systems).

IMO this idea with copying is in itself even less sane than init using rlimits on PID 1.

Not to mention that rlimits use signals for communicating when you've started to hit some of the limits.

It might be better to use proper rlimits, and not let a mad process gone wild triggers the OOM.

It can change its own rlimits, sure, but it needs to do that within its existing 8 MB stack.

Not to mention that you can limit the amount of kernel memory used by a process (not possible with rlimits).

Also, rlimits have interesting interactions once a process starts changing its user ID or session ID.

The rlimits for open files and similar things are just not useful for things like that.

Another is that as far as security is concerned, I don't think they provide more restrictions than rlimits.

There are established guides to configuring qmail that tell you to set rlimits.

I guess I'm just annoyed that we can't use "better rlimits" with "rootless" container runtimes because of all of this.