[ale] [Fwd: Advertising on ale.org] - OT MS vs Apple vs Linux/UNIX

[Solomon Peachy]

On Sat, Sep 12, 2015 at 03:33:32PM -0700, Alex Carver wrote:
> It's a bit confusing and probably not well written but when trying to
> find any information on something very new and unfamiliar it's hard to
> separate out any mistakes.

Fair enough.  there's no shortage of bad or confusing documentation out 
there.  I'm personally responsible for far more than I care to admit.  :)

But in this case, they were using PulseAudio as common system service 
that could be started up via systemd.

> Ok, no one ever describes *how* nor do they ever really mention it.
> It's not even in the FAQ on the project page.

From the systemd man page: 

  SIGTERM:
           Upon receiving this signal the systemd system manager serializes
           its state, reexecutes itself and deserializes the saved state
           again. This is mostly equivalent to systemctl daemon-reexec.

The recommended way is using the systemctl invocation, which is also in 
the systemctl man page:

       daemon-reexec
           Reexecute the systemd manager. This will serialize the manager
           state, reexecute the process and deserialize the state again. This
           command is of little use except for debugging and package upgrades.
	   [ .. and some more stuff .. ]

FWIW your distro upgrade scripts should automatically invoke this.

> That's what I was trying to do, but even the project page seems to be
> slim on documentation beyond how to use the feature (missing would be
> maintenance, lower level control, etc.)

All of the latter is covered by the generic service handling 
documentation -- to systemd, there's no real difference between, say, 
bringing up your network, and bringing up a daemon.  Each is just a 
"service" with its own set of dependencies.

> Bringing up a network interface (which almost always are static in my
> case) and bringing up a DHCP server are two different things.  I used
> this as an example only and not really intending to be specific to DHCP
> but more to identify a situation where a systemd module has more than
> one responsibility (in this case networkd has network interface, DHCP
> client and DHCP server).  I was not really understanding how to have one
> feature without the others.  Back with the DHCP example it's not obvious
> or intuitive how to allow a static interface to be brought up, not
> invoke a DHCP client on that interface (since a static IP doesn't need
> it) and also prevent the systemd DHCP daemon from starting which would
> interfere with a preferred daemon even though all three of those
> features are within the networkd portion of systemd.

In the most basic sense, to bring up your own network you'd create a 
systemd 'network.service' definition that includes the details on how 
you want your network to be brought up -- eg a set of command 
invocations, or invoking a dhcp client.

To run a dhcp server, you'd just create a 'dhcpd.service' definition 
that includes details on how to get your preferred dhcp server running.  
You'd probably want it to depend on network.service' since it's rather 
useless without the network being up (and can be made to automatically 
restart should the network itself be restarted)

How you make these things interact is actually up to you.  They provide 
recommendations for best practices, but you're free to ignore all of
that.

 - Solomon
-- 
Solomon Peachy        		       pizza at shaftnet dot org
Delray Beach, FL                          ^^ (email/xmpp) ^^
Quidquid latine dictum sit, altum viditur.
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