[Nix-dev] Directly configuring sysfs or /sys (not sysctl)

[Roger Qiu]

Just listing the current possible methods for configuring /sys (I 
haven't tried all of them):

* Configuring a custom systemd service to run on boot that just executes 
something like `bash -c 'echo ... > /sys...`
* Setting up a udev rule: http://serverfault.com/a/636759/147813
* Use systemd's tmpfiles.d and write a rule that writes a parameter to 
/sys: http://www.freedesktop.org/software/systemd/man/tmpfiles.d.html
* Use `/etc/sysfs.conf` or `/etc/sysfs.d/` and package up the systemd 
sysfsutils.service (this doesn't exist in Nix/NixOS currently).

Perhaps the primitive in Nix could use of them as a backing. The 
configuration primitive could be`boot.kernel.sys` or `boot.sys`.

On 24/05/2015 3:25 AM, Roger Qiu wrote:
> Hi,
>
> I was wondering if there was a particular Nix/NixOS configuration 
> primitive that allowed direct & permanent editing of arbitrary sysfs 
> `/sys` parameters?
>
> Currently it seems that it's possible by creating custom systemd 
> services (or maybe a udev rule) that run at boot which set the 
> settings, or you could use `|/etc/sysfs.conf|.` or `/etc/sysfs.d/` 
> (but I'm not sure if these are enabled in NixOS).
>
> Unlike sysctl settings which are clearly explained in the 
> documentation, it's not clear where the canonical place to set `/sys` 
> settings should be such as CPU frequency.. etc.
>
> Thanks,
> Roger
>
> -- 
> Founder of Matrix AI
> http://matrix.ai/
> +61420925975
>
> -- 
> Founder of Matrix AI
> http://matrix.ai/
> +61420925975
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