CentOS - Dec 2016 - CentOS 7 and systemd: SysV initscript: how detect boot vs. interactive use?

James Hogarth <james.hogarth at gmail.com>
wrote:
>On 18 Dec 2016 10:59, "whitivery" <co55-sy1t at
dea.spamcon.org> wrote:
>
>Moving from CentOS 5 to CentOS 7, discovered that a test in a SysV
>initscript for whether it is running interactively, instead of at boot
>time, no longer works.
>
>Under CentOS 7 / systemd, is there some way for the initscript to know
>this?
>
>
>Generally "interactive" init scripts are not in any way supported
under any
>RHEL version and can't be done under systemd on EL7
>
>What is it that it does and you are actually trying to achieve?
>
>If it's a password or something like that it's possible to integrate
with
>the systemd-ask-password facility from a unit file, but it is quite complex
>relatively speaking so it'd be useful to know the actual goal in mind
>before going down this road.
It is a system with several servers (various platforms/distros).

One piece of software runs on all of the servers.  For it to operate
correctly, the instance on one server (prime) must start before the others
(auxiliary).

So a boot delay is added (via a script sourced from initscript, which
first waits for network to come up) to set the boot delay values for each
server - prime at 0, others at some other value of 15 to 110 seconds
depending on platform.

But when it is necessary to manipulate the service interactively via the
"service" command, the boot delay needs to be bypassed.

On Sun, Dec 18, 2016 at 08:50:54PM -0800, whitivery
wrote:
> It is a system with several servers (various platforms/distros).
> 
> One piece of software runs on all of the servers.  For it to operate
> correctly, the instance on one server (prime) must start before the others
> (auxiliary).
> 
> So a boot delay is added (via a script sourced from initscript, which
> first waits for network to come up) to set the boot delay values for each
> server - prime at 0, others at some other value of 15 to 110 seconds
> depending on platform.
> 
> But when it is necessary to manipulate the service interactively via the
> "service" command, the boot delay needs to be bypassed.
Well, the first thing I'd do is make the service wait for the network
to be online.  In the [Unit] section add Wants=network-online.target.

Secondly, I'd try to find a way for the auxiliary services to ping the
prime service to ensure its up, and make that script a ExecStartPre
entry in the [Service] section.  You'll want to adjust the
TimeoutStartSec in case it might exceed the DefaultTimeoutStartSec in
/etc/systemd/system.conf, which is 90 seconds.

-- 
Jonathan Billings <billings at negate.org>

Jonathan Billings <billings at negate.org>
wrote:
>On Sun, Dec 18, 2016 at 08:50:54PM -0800, whitivery wrote:
>> It is a system with several servers (various platforms/distros).
>> 
>> One piece of software runs on all of the servers.  For it to operate
>> correctly, the instance on one server (prime) must start before the
others
>> (auxiliary).
>> 
>> So a boot delay is added (via a script sourced from initscript, which
>> first waits for network to come up) to set the boot delay values for
each
>> server - prime at 0, others at some other value of 15 to 110 seconds
>> depending on platform.
>> 
>> But when it is necessary to manipulate the service interactively via
the
>> "service" command, the boot delay needs to be bypassed.
>
>Well, the first thing I'd do is make the service wait for the network
>to be online.  In the [Unit] section add Wants=network-online.target.
>
>Secondly, I'd try to find a way for the auxiliary services to ping the
>prime service to ensure its up, and make that script a ExecStartPre
>entry in the [Service] section.  You'll want to adjust the
>TimeoutStartSec in case it might exceed the DefaultTimeoutStartSec in
>/etc/systemd/system.conf, which is 90 seconds.
Thank you for the idea, but as mentioned, the same service runs on a mix
of server platforms and distros, and the older ones do not use systemd, so
I'd prefer to stick with SysV type initscripts that work on all of them.