[Buildroot] swapoff, but no swapon in initab

Arnout Vandecappelle arnout at mind.be
Wed Jun 20 20:13:12 UTC 2018



On 20-06-18 10:42, Peter Korsgaard wrote:
>>>>>> "Arnout" == Arnout Vandecappelle <arnout at mind.be> writes:
> 
>  > On 12-06-18 16:50, Peter Korsgaard wrote:
>  >>>>>>> "Arnout" == Arnout Vandecappelle <arnout at mind.be> writes:
>  >> 
>  >> >> But it does require people to add swapon/swapoff to their busybox config
>  >> >> even if they aren't using swap, otherwise they would get error messages
>  >> 
>  >> >  I think if people start customizing the busybox config and remove stuff from
>  >> > it, then it's only reasonable that they also modify the default
>  >> > inittab.
>  >> 
>  >> Correct.
>  >> 
>  >> > Swaponand swapoff are both enabled in our busybox.config and busybox-minimal.config.
>  >> 
>  >> Hmm, does swap work on nommu? I would guess not. Looking at the kernel
>  >> option:
> 
>  >  Doesn't matter if it works or not; if the swapon executable exists, then the
>  > swapon in inittab will pass without error (if you don't have swap configured in
>  > fstab). Clearly, the swapon will fail if you indeed have swap enabled in fstab
>  > on a NOMMU system, but I don't think we have to protect against that situation,
>  > right? It will anyway also fail if you don't have swap enabled in the kernel.
>  > Just like mounting the ext2 rootfs will fail if you don't have ext2/3/4 enabled
>  > in your kernel...
> 
> Yes, so the only minor issue is that we need to have swapon/swapoff
> enabled in busybox-minimal.config even though it isn't useful just to
> not get an error message during bootup/shutdown.

 Well, it currently _is_ enabled in busybox-minimal.config... Admittedly, this
adds almost 1KB to the busybox size so perhaps it should be removed from
-minimal. But the we probably should also remove swapoff from inittab. Hell,
perhaps we should do that anyway, since doing swapoff for reboot is utterly
useless IMO.

 Regards,
 Arnout


-- 
Arnout Vandecappelle                          arnout at mind be
Senior Embedded Software Architect            +32-16-286500
Essensium/Mind                                http://www.mind.be
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