device tarball needs to allow setting sysctl defaults

[Oliver Grawert]

the raspberry Pi uses an smsc95xx USB NIC ... there is an ancient bug with this hardware (Bug #664477) that requires that vm.min_free_kbytes is set to 8192 in the sysctl settings. while it is possible to ship a /system/etc/sysctl.d/nn-smsc95xx.conf file in the device tarball, once this is switched to be a snap package we need a way to allow shipping such files and potentially adjust their values via snappy config.

[Zygmunt Krynicki (zyga)]

I'm marking this bug as won't fix as it was reported in snapd 15.04 era. Please re-open with updated information if the original issue is still a problem for you.

[Oliver Grawert (ogra)]

that it comes from the 15.04 aera doesnt really make it invalid, this is still a missing feature (that gets hacked around via initrd scripts or injected hacks during image creation today in undesired ways)

[Zygmunt Krynicki (zyga)]

Interestingly we once had a sysctl backend in snapd but it was never merged (it morphed into the systemd backend). I can whip up something if you would give ma an example of what should happen.

[Samuele Pedroni (pedronis)]

we started adding some support for setting sysctl params (it really covers one kernel param atm) via snap set system