[OE-core] [PATCH 1/1] systemd: make /etc/sysctl.conf have real effect

[ChenQi]

On 11/07/2014 06:38 AM, Randy Witt wrote:
> On 11/06/2014 05:29 AM, Koen Kooi wrote:
>>
>> Op 6 nov. 2014, om 12:59 heeft ChenQi <Qi.Chen at windriver.com> het 
>> volgende geschreven:
>>
>>>
>>>
>>> On 11/06/2014 06:33 PM, Koen Kooi wrote:
>>>>> Op 6 nov. 2014, om 08:59 heeft ChenQi <Qi.Chen at windriver.com> het 
>>>>> volgende geschreven:
>>>>>
>>>>> On 11/06/2014 03:48 PM, Koen Kooi wrote:
>>>>>> Op 6 nov. 2014, om 08:32 heeft Chen Qi <Qi.Chen at windriver.com> 
>>>>>> het volgende geschreven:
>>>>>>
>>>>>>> In systemd, /etc/sysctl.conf is actually ignored by systemd-sysctl,
>>>>>>> because this command only examine *.conf files under a bunch of 
>>>>>>> directories
>>>>>>> like /etc/sysctl.d or /usr/lib/sysctl.d.
>>>>>>>
>>>>>>> The problem is we are used to configuring kernel parameters in 
>>>>>>> /etc/sysctl.conf,
>>>>>>> so it would be really strange if the configuration in that file 
>>>>>>> doesn't have any
>>>>>>> effect.
>>>>>>>
>>>>>>> This patch reference Fedora's solution to this problem, creating 
>>>>>>> a symlink to
>>>>>>> /etc/sysctl.conf under /etc/sysctl.d/.
>>>>>> Shouldn't this be done in procps instead?
>>>>>>
>>>>> Actually, the problem is not about `sysctl' command.
>>>>> procps provides `sysctl', but busybox also provides this command.
>>>>> It's very possible that on our generated image, procps is not 
>>>>> installed but `sysctl' command is available.
>>>>> Both busybox's and procps's `sysctl' command takes 
>>>>> /etc/sysctl.conf into consideration.
>>>> Right, but only procps installs that file.
>>>
>>> As busybox provides `sysctl' utility, is it reasonable that it also 
>>> provides a corresponding configuration file (/etc/sysctl.conf)? 
>>> Should we make a patch for busybox?
>>>
>>>
>>>>> Now, systemd provides a similar utility called `systemd-sysctl' 
>>>>> which is executed at boot time via systemd-sysctl.service.
>>>>>
>>>>> So our actually problem is that systemd-sysctl ignores 
>>>>> /etc/sysctl.conf, which makes it somewhat strange, especially to 
>>>>> users who are used to configuring parameters in sysctl.conf.
>>>>> And this patch solves this problem by adding a symlink under 
>>>>> /etc/sysctl.d/.
>>>>>
>>>>> That's why I think we should put this in systemd.
>>>> You're adding a symlink to a file which only exists if you install 
>>>> procps, which isn't in RDEPENDS.
>>>>
>>>
>>> As I said before, procps is *not* necessary for the sysctl mechanism 
>>> to have effect.
>>> (Think about systemd-based core-image-minimal image.)
>>>
>>> Busybox provides `sysctl', systemd provides `systemd-sysctl'.
>>> (It's an easy program, there might exist other packages that provide 
>>> it too.)
>>>
>>> /etc/sysctl.conf is a configuration file which is very likely to be 
>>> modified or created by administrators to configure kernel parameters.
>>> (You can't expect administrators to all start learning systemd, 
>>> trying to understand the gap and differences. In addition, they may 
>>> have scripts that edit /etc/sysctl.conf to automate their work.)
>>>
>>> The point of the symlink is to ensure that when users edit 
>>> /etc/sysctl.conf (or create one), configurations in that file will 
>>> have effect at boot time.
>>>
>>> Just think about this problem from a standpoint of user experience.
>>
>> You still haven't convinced me that shipping a broken symlink is a 
>> good idea. I'm pretty sure it's not even allowed in out commit 
>> guidelines.
>>
> I agree, even in Fedora's case, both /etc/sysctl.conf and 
> /etc/sysctl.d/99-sysctl.conf come from the same package, 
> initscripts-9.51-2.
>
>

Koen & Witt,

When I started out to solve this problem, I basically came up with three 
solutions. Please see details below. I chose to use solution 3 because I 
think it's better than the other two. Please tell me which one you like, 
or please tell me your solution.

Solution 1:
Make 'sysctl.conf' managed by ALTERNATIVES mechanism in OE. Busybox, 
procps and systemd all provide this file. And the symlink is still in 
systemd.
(My opinion for this one: over engineering)

Solution 2:
Make base-files provide sysctl.conf and /etc/sysctl.d/99-sysctl.conf (in 
case of systemd). procps no longer provides sysctl.conf.
(My opinion for this one: sysctl.conf doesn't logically belong to 
base-files.)

Solution 3:
Let systemd provide a broken symlink '/etc/sysctl.d/99-sysctl.conf' and 
don't change anything else.

Which of the above three solutions do you like? Do you have any other 
suggestion?

//Chen Qi