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

[Carlo Zancanaro <carlo@zancanaro.id.au>]

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Hey Ludo’,

On Sat, Sep 01 2018, Ludovic Courtès wrote:
> I’d like to make sure we understand the story with ‘EINTR-safe’, 
> but after that I’m happy to push a release.

Do you have any thoughts about why it could be failing, or things 
I could investigate? I don't know where to start.

>> One possible improvement would be to print out the services 
>> that need to be restarted to be upgraded.
>
> Yes, that’d be nice.

I have done this, but now it seems a bit overwhelming how many 
services would need to be manually restarted. My modified code 
writes a message like this:

To complete the upgrade, restart the following services:
    file-systems
    user-file-systems
    file-system-/boot/efi
    file-system-/dev/pts
    file-system-/dev/shm
    file-system-/gnu/store
    file-system-/run/systemd
    file-system-/run/user
    file-system-/sys/fs/cgroup/elogind
    file-system-/sys/fs/cgroup
    file-system-/sys/fs/cgroup/cpuset
    file-system-/sys/fs/cgroup/cpu
    file-system-/sys/fs/cgroup/cpuacct
    file-system-/sys/fs/cgroup/memory
    file-system-/sys/fs/cgroup/devices
    file-system-/sys/fs/cgroup/freezer
    file-system-/sys/fs/cgroup/blkio
    file-system-/sys/fs/cgroup/perf_event
    root-file-system
    user-processes
    host-name
    udev
    nscd
    guix-daemon
    urandom-seed
    syslogd
    loopback
    term-tty6
    term-tty5
    term-tty4
    term-tty3
    term-tty2
    term-tty1
    console-font-tty1
    console-font-tty2
    console-font-tty3
    console-font-tty4
    console-font-tty5
    console-font-tty6
    virtual-terminal
    ntpd
    dbus-system
    elogind
    upower-daemon
    avahi-daemon
    wpa-supplicant
    networking
    xorg-server
    cups

The same list is printed every time on my system, because the 
diffing is only on the level of the canonical-name. Most of these 
services are being "replaced" by services that are exactly the 
same, so they don't really need to be restarted. I don't really 
know what to do about this, Even if it were fixed, on an actual 
upgrade I assume many of these services would be different, and 
thus would be printed legitimately.

I'm also confused why some of these things are services (like 
host-name).

I'll send through an updated patch once I've cleaned it up a bit, 
but I'm not as positive about it as I was initially.

Carlo

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