DietPi System Preparation | Add sysctl config values to our own .conf file

[MichaIng]

• Generally we should try to add our values into our own files, if a '*.d/' folder exists. This enables package updates to overwrite the unchanged main .conf without overwriting our values.
• I chose "97-" prefix here as "99-" is used by systemd and "98-" by RPi raspberrypi-sys-mods.
• We could also check for/sed existing vm.swappiness entries, but I guess '/*.d' entries will overwrite anyway?

[Fourdee]

If we use > here, it will overwrite the file with the entry. >> will append to end of existing file, if it exists (multiple entries if command used again with >>, not with >)

[MichaIng]

Oh important point, thus > is necessary here, or touch filename first, if we add something earlier/optional.

[Fourdee]

@MichaIng

Generally we should try to add our values into our own files, if a '*.d/' folder exists.

Agree 👍

We could also check for/sed existing vm.swappiness entries, but I guess '/*.d' entries will overwrite anyway?

https://github.com/Fourdee/DietPi/pull/1247/files#r152038845

[MichaIng]

Yes, as we create and and just set this value so far, no check necessary. We could just check the other config files if some other package/default sets it also. I am not sure about priorities, if it is set multiple times in different configs, could run some checks about this later.

[MichaIng]

@Fourdee
Just evidentially found my test of echo -e "vm.swappiness=1" >> /etc/sysctl.d/97-dietpi.conf and even that >> is used, the file is also created if not existent, at least here on Jessie and Stretch. Thus we can just always use >> and don't need to think about if it's already there or not. Of course we should prevent double entries, but not as long as we just create and write the file in system preparation script 😉.

But I will leave the > for now, as it does not matter here.