[systemd-devel] [solved] howto handle one time shutdown programs

[Andreas Buschmann]

Hello Andrei,

On Tue 30-Jun-2015 15:45 CEST Andrei Borzenkov writes:

> On Tue, Jun 30, 2015 at 2:35 PM, Andreas Buschmann <buschman at tech.net.de> wrote:
>> Hello Johannes,
>>
>> On Thu 25-Jun-2015 20:09 CEST Johannes Ernst writes:
>>
>>>> On Jun 25, 2015, at 7:57, Andreas Buschmann <buschman at tech.net.de> wrote:
>>>>
>>>> I am writing a systemd .service file to handle NVDIMMs.
>>>>
>>>> - start
>>>> - stop
>>>> - reload
>>>> all work
>>>>
>>>> The problem child is "restart".
>>>> Restart is internally implemented as stop followed by start.
>>>>
>>>> The problem is, that stop calls a program which does something to the
>>>> NVDIMM hardware.
>>>> After that no further access to the NVDIMMs is possible before the next
>>>> reboot of the server.
>>>>
>>>> How should I handle that sort of logic with systemd?
>>>
>>> How is that different from the user executing:
>>>
>>> systemctl start your.service
>>> systemctl stop your.service
>>> systemctl start your.service
>>>
>>> without reboot?
>>
>> It is not different, but that sequence can not work with my
>> implementation of the service.
>>
>> systemctl stop your.service
>> can only be called once.
>>
>> My stop script shuts down the hardware.
>> Think like parking a hard disk.
>>
>>
>> I am not sure on how to do that the systemd way.
>>
>> I have no problem with spliting the service up into
>> myservice1 and myservice2, but than myservice2 has to be called exactly
>> once before a shutdown or a reboot completes.
>>
>
> You could place separate shutdown hook in
> /usr/lib/systemd/system-shutdown/. Note that all executables there are
> run concurrently in case it matters.

It works.
But only if everything you need is in the root filesystem.

It would be helpful if the man page for 
  man systemd-shutdown
would be extended by:

-------------------------------------------------------------------------------
The executables in /usr/lib/systemd/system-shutdown only have access to
the root filesystem (/).
All other filesystems are not mounted any more.
The remaining mounts are:
/proc
/sys
/dev

For debugging these scripts redirect your output to /dev/ttyS0 or
/dev/ttyS1 and log that output over a serial console switch.
-------------------------------------------------------------------------------

					Mit freundlichen Gruessen
						Andreas Buschmann
-- 

Andreas Buschmann
[Senior Systems Engineer]

net.DE AG
Büttnerstraße 57
D-30165 Hannover