On Saturday 8 February 2025 23:07:38 Greenwich Mean Time Jack wrote:
> On 2025.02.08 14:00, Filip Kobierski wrote:
> > Hi Jacques,
> > 
> > I think you are looking for SIGSTP or SIGSTOP but I think that's
> > not exactly it. From what I know you cannot do that for emerge
> > easily. For similar results you might want to set up ccache.
> > https://wiki.gentoo.org/wiki/Ccache
> > 
> > Regards
> > Filip
> > 
> > On Saturday, February 8th, 2025 at 15:47, Jacques Montier
> > 
> > <jmontier@gmail.com> wrote:
> > > Hello everyone,
> > > Is it possible to stop a compilation midway in the case of a very
> > 
> > long compilation and then resume it from the same point without
> > having to start over from the beginning ?
> > 
> > > Thank you for your response.
> > > Best regards,
> > > 
> > > --
> > > Jacques Montier.
> 
> If you really mean just interrupting a compile, then you should be able
> to stop with Ctl-C, and then start/continue by running make or ninja
> again, assuming that is what is used for whatever you are compiling.
> Ccache can help since most of the results of the previous compile
> attempt will have been cached, and so will be completed more quickly
> the next time, but it's not the same as continuing from where it was
> interrupted.
> 
> If, as Filip implies, you are asking about interrupting emerge, it's
> easy enough to interrupt, but essentially impossible to continue from
> where it left off.  "emerge --continue" will just try to emerge every
> package from the interrupted emerge which was not completed, but it
> will start each one from scratch.  What has often, but not alwasy
> worked for me, is to use ebuild directly.  "ebuild
> .../path/to/package.ebuild compile" will figure out that everything
> prior to the compile was completed, and then issue the make or ninja
> commands, which will just pick up where they left off.  If that does
> work, then you need to repeat the ebuild, but with the install and then
> the qmerge commands.  The only problem with that (for me, at least) is
> that ebuild does not leave exactly the same lines in emerge.log, so a
> package installed that way will not show up in "gentlop -t package"
> output.

You can run 'ebuild <package> merge', but this will only continue with the 
last package you were emerging when it was interrupted and it will continue 
from whatever stage the emerge was at the time it was interrupted.

If your intention is to suspend/hibernate the OS halfway through an emerge and 
continue later on, then you can suspend the emerge job with job control:

Ctrl+z

After you wake up the system from suspend or reboot from hibernate you can 
bring the emerge job back into the foreground, so it can continue running from 
where you left it, by invoking:

fg

NOTE:  Depending how many threads you were running before you suspended the 
emerge and how much swap was being used, you may need to wait for a few 
minutes for all the threads to pause.  Keep an eye on top to confirm this has 
taken place and the CPU is now idle, before you suspend/hibernate the OS.  If 
you don't you could discover the suspend/hibernate fails if you do not have 
enough RAM/space.