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by woodman 4179 days ago
The linux sysctl is a wrapper for kernel state represented in the file system, freebsd sysctl is direct to kernel. So that is nice, everything in one place. Before my switch to freebsd, I had been a linux user since 2000 - and while I was aware of the existence of sysctl, I don't remember seeing it used very often. It was much more common to see direct interaction with stuff in /proc (rockectraid, never again). Why is that? Is it an issue with standardizing driver interaction or what?

My prior post wasn't written as a statement of exclusivity, simply that I prefer the way freebsd does it.
1 comments
caf 4179 days ago
The /proc/sys/ and sysctl(2) methods are really just down to which syscall is used to talk to the kernel - either way it's just reading or writing a kernel-side data structure, there's no fundamental difference there.

The /proc/sys/ pseudo-filesystem interface has the advantage that it's discoverable. The sysctl(2) interface requires userspace to have knowledge of a swag of hardcoded ID numbers identifying each node in the sysctl tree.

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woodman 4179 days ago
I haven't poked through the code, but the linux man page isn't encouraging: "use the /proc/sys interface instead" [0]

Compare that to the freebsd man page [1]

[0] http://man7.org/linux/man-pages/man2/sysctl.2.html#NOTES

[1] https://www.freebsd.org/cgi/man.cgi?query=sysctl&sektion=3&m...

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caf 4179 days ago
I think perhaps we might be talking at cross-purposes here.

My point is that when you call write(2) under Linux on a file descriptor derived from opening a /proc/sys pseudo-file you are talking directly to the kernel code responsible for updating the sysctl variables in the same way as you are when you call sysctl(2) under FreeBSD.

The /proc/sys files aren't real files - they're just a way of representing the sysctl variables in the existing file namespace.

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woodman 4179 days ago
Ah, when you said sysctl(2) I thought you were talking about the linux call - which is basically dead code. Yeah I don't really have a beef with the whole "everything is a file" design, I actually quite like it, but I really like how well freebsd has done sysctl - both the subroutine (3) and the command (8).
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