[Spice-devel] [PATCH spice-vdagent] service: simplification and accessability - reversion

[poma]

On 19.10.2015 19:27, Hans de Goede wrote:
> Hi,
> 
> On 19-10-15 16:55, poma wrote:
>>
>> While testing, I came to the same conclusion as Marc-André - commit 1587063.
>>
>> Hans, why the complexity of the "rules & target", isn't "ConditionPath*" sufficient?
>> Besides, the lack of "WantedBy=multi-user.target" - back and forth with 'graphical.target' - 'spice-vdagentd' is "lost".
>>
>> Obviously X session (e.g. w/ 'startxfce4') can also start within 'multi-user.target',
>> so why start 'spice-vdagentd' manually, unnecessarily, when sufficient is to append "multi-user.target", i.e.
>> "WantedBy=spice-vdagentd.target multi-user.target"
>>
>>
>> Simplifies start-up scheme and makes 'spice-vdagentd' more accessible as service.
>>
>> Tested-by: poma <pomidorabelisima at gmail.com>
> 
> Nack, the spice-vdagent is a hardware service (even if it is virtual hardware),
> systemd has a well-documented standard mechanism for hardware activation, and that is
> what is being used. Using ConditionPathIsSymbolicLink is just a hack to achieve more
> or less the same (mostly less, e.g. if the port ever becomes a hotplugable device
> in the future the hack will not work).
> 
> Regards,
> 
> Hans
> 

Right!

http://man7.org/linux/man-pages/man7/daemon.7.html
- Device-Based Activation -

http://0pointer.de/blog/projects/socket-activation2.html
- Hardware Activation in Detail -

But still need constant availability - hence the term "service", in both directions:
graphical.target <-> multi-user.target

So spice-vdagentd.service here, is composed as follows:

[Unit]
Description=Agent daemon for Spice guests
After=dbus.target
ConditionPathIsSymbolicLink=/dev/virtio-ports/com.redhat.spice.0

[Service]
Type=forking
EnvironmentFile=-/etc/sysconfig/spice-vdagentd
ExecStartPre=/bin/rm -f /var/run/spice-vdagentd/spice-vdagent-sock
ExecStart=/usr/sbin/spice-vdagentd $SPICE_VDAGENTD_EXTRA_ARGS
PIDFile=/var/run/spice-vdagentd/spice-vdagentd.pid
PrivateTmp=true

[Install]
WantedBy=spice-vdagentd.target multi-user.target


"ConditionPathIsSymbolicLink" is a check, so the service will not re/start if there is no point.