bug#22039: [PATCH] 'guix system reconfigure' must start/restart/stop services

[Carlo Zancanaro]

> [...] so presumably messages go to /dev/kmsg and/or the console.

I don't remember seeing anything about the exception in any of the 
output that I looked at. I'm a bit confused about where different 
bits of output go, so I'll take a look at how output is handled in 
a few weeks, when the rest of life settles down a bit.

> I wouldn’t consider it a blocker for 0.5.0 though.  WDYT?

Yeah, I agree. We should try to improve it, but as long as we 
haven't made things worse (which we haven't) then it shouldn't 
block a release.

We still need to work out what we want to do on the Guix side once 
the Shepherd is released. Do we want to restart services that we 
can, or print a message telling users how to do so? Maybe 
individual services should be able to specify their preference?

Carlo