[Spice-devel] [vdagent-linux v2] systemd: Remove unneded virtio-port dependencies

[Frediano Ziglio]

> On Wed, Dec 19, 2018 at 09:52:57AM -0500, Frediano Ziglio wrote:
> > The "Requisite" still prevents the socket to be activated with a
> > "systemctl enable spice-vdagentd.socket" launched manually.
> > You can obviously complaint that users should not do that but
> > I don't think that if the system says "you don't have the device
> > needed" when effectively don't have the needed device is a bad
> > approach. So personally I would like to keep the "Requisite".
> > About the "After" I have no idea of the difference that it can
> > make.
> 
> If you want some strong relationship like this, maybe we should change
> it to BindsTo:
> BindsTo=
>    Configures requirement dependencies, very similar in style to Requires=.
>    However, this dependency type is stronger: in addition to the effect of
>    Requires= it declares that if the unit bound to
>    is stopped, this unit will be stopped too. This means a unit bound to
>    another unit that suddenly enters inactive state will be stopped too.
>    Units can suddenly, unexpectedly enter inactive state
>    for different reasons: the main process of a service unit might terminate
>    on its own choice, the backing device of a device unit might be unplugged
>    or the mount point of a mount unit might be
>    unmounted without involvement of the system and service manager.
> 
>    When used in conjunction with After= on the same unit the behaviour of
>    BindsTo= is even stronger. In this case, the unit bound to strictly has
>    to be in active state for this unit to also be in
>    active state. This not only means a unit bound to another unit that
>    suddenly enters inactive state, but also one that is bound to another
>    unit that gets skipped due to a failed condition check
>    (such as ConditionPathExists=, ConditionPathIsSymbolicLink=, ... — see
>    below) will be stopped, should it be running. Hence, in many cases it is
>    best to combine BindsTo= with After=.
> 
> Christophe
> 

Looking at vdagent options you can specify also the device so in theory you
could configure the agent to use a different device or a socket so would
make sense to have the socket active.
As the user would have to manually enable/activate the socket giving
error or not is just an opinion.

Frediano