why do we use systemd?

[lee]

Patrick O'Callaghan <pocallaghan at gmail.com> writes:

> On Sat, 2014-07-05 at 22:07 -0400, Garry T. Williams wrote:
>> The systemd(1) manual page uses the term "entity" -- not object to
>> refer to units.  And it says units encapsulate various objects.
>> Perhaps this is the source of confusion?
>
> The word "entity" is not used anywhere in the systemd(1) man page. The
> plural "entities" is used exactly once, in the phrase "systemd provides
> a dependency system between various entities called "units" of 12
> different types". So apparently entity==unit.

There could be other entities somewhere that aren't units and aren't
mentioned in the man page.  Or perhaps they are but aren't called that.

However, according to [1], "entity" is a synonym for "unit".  So what
exactly does the quoted sentence from the man page try to explain?


[1]: http://thesaurus.com/browse/unit

> The term "object" is used twice. Once is in reference to "file system
> objects" which I assume has the usual meaning. The other is in "Units
> encapsulate various objects that are relevant for system boot-up and
> maintenance".
>
> So to sum up: systemd manages dependency relations between entities
> called units. Units encapsulate objects in 12 different ways. Objects
> are <insert hand-waving here>

It's much simpler: "systemd provides a dependency system between <insert
hand-waving here> which are/is encapsulated in 12 different types".

So what does it actually do?

And I can only guess that it's called "systemd" because it provides a
"system" and is a daemon.  But is it a daemon?  Looking at [2], it is
not because it's controlled by a user (through systemctl and
journalsomething and perhaps other things I don't know about).

Actually, it's more like an MCP, if you've seen Tron.


[2]: https://en.wikipedia.org/wiki/Daemon_(computing)


> I repeat that I am not attacking systemd here, I'm criticizing the way
> it's described. It may seem perfectly clear to those who already
> understand it, but it's not at all clear to those who are used to
> something different.

The documentation is just badly written.  What do you expect when
"disabled" means something like "not so much enabled" and "mask" means
"disabled"?  I made a bug report about that, and they decline to even
fix a simple thing like that.


-- 
Fedora release 20 (Heisenbug)