[systemd-devel] [PATCH] Remove device and its relatives when action is offlined

[Lennart Poettering]

On Mon, 09.09.13 17:23, MUNEDA Takahiro (muneda.takahiro at jp.fujitsu.com) wrote:

> Ok, I found out another problem.
> Even if I have a following udev rules and 'remove' event happens, no 
> systemd service will be called.
> 
>   ACTION=="add|remove", TAG+="systemd", ENV{SYSTEMD_WANTS}="muneda at .service"
> 
> My final goal is to invoke my systemd service which calls programs 
> that needs a bit long time when I do add/online or remove/offline my 
> device.  udev provided this feature before it's merged into systemd.  
> My previous patch let 'offline' event to remove device information 
> from systemd (probably, remove from udev database?), but systemd does 
> not call service as I expected.

systemd only cares for add and remove events, nothing else, and will do
so only for devices tagged with the "systemd" udev tag. It will
activate devices when "add" is sent, and deactivate them when "remove"
is sent. You can pull in arbitrary services via SYSTEMD_WANTS (which
causes a "Wants" type dependency from the device unit be created to the
specified service unit. And you can bind units back to the device unit
via "BindsTo=" in the service unit.

The udev rule above will not work, as you are can only add dependencies
to to instantiated unit names. Try
ENV{SYSTEMD_WANTS}="muneda@%k.service" or suchlike, instead. Also,
ACTION="remove" doesn't make much sense for this...

Lennart

-- 
Lennart Poettering - Red Hat, Inc.