[CentOS] Cemtos 7 : Systemd alternatives ?

David Both dboth at millennium-technology.com
Tue Jul 8 01:32:08 UTC 2014



On 07/07/2014 08:46 PM, Robert Moskowitz wrote:
> On 07/07/2014 07:47 PM, Always Learning wrote:
>> Reading about systemd, it seems it is not well liked and reminiscent of
>> Microsoft's "put everything into the Windows Registry" (Win 95 onwards).
>>
>> Is there a practical alternative to omnipresent, or invasive, systemd ?
>>
> So you are following the thread on the Fedora list?  I have been
> ignoring it.
>
> Best I can tell is learn it and use it.  And if you have any services,
> fix them so that they work with systemd.  I work with one that does not
> and it is very slow to complete its startup.
>
As far as I know there is no going back to SystemV at this point and I am fine 
with that.

systemd is just fine. It has been around on Fedora for a few releases now. It is 
quite compatible with old SystemV start scripts and systemd simply uses the 
SystemV start scripts as configuration files to start those services.

What you are probably seeing is the result of a side effect of the new systemd 
strategy. systemd only starts services when they are actually needed. systemd 
does this by simply creating a socket on which it listens for requests for that 
service. The service is only started when a request is made to that socket. Of 
course some services are up and running from the beginning, but those not needed 
are left to load and start when a request is made on the socket for that 
service. So the delay in starting your SystemV service means that your service 
is waiting for a reply from a service on which it depends and which has not yet 
been started. systemd receives the request from your service on the socket 
intended for the service yours is requesting. systemd then starts that service 
and returns the result - after a bit of a delay - to your SystemV service. After 
the first request to the systemd managed service, there should be no further 
delays. Unless the service is seldom used and systemd determines it can remove 
the service from memory with minimal impact.

I like systemd a lot. I still like SystemV a lot, too.

I have a page on one of my web sites that does not explain systemd, but rather 
provides a number of very good links that do explain it - in morbid detail. 
These links also discuss the philosophy behind the change. Good reading!

http://www.databook.bz/?page_id=2578

The latest Fedora documentation has good information about using systemd to 
manage services and managing and configuring systemd itself.

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