Linked by Dennis Heuer on Wed 25th Aug 2010 22:23 UTC
Linux I came across a news entry at Phoronix about a new init replacement, systemd, and curiously started a read into the surprisingly heavy matter. Systemd is by no means as simple as upstart. It does far more things far more straight and in more detail. The differences are so significant that they enforce quite different configuration strategies. One can argue for both, depending on the goal to reach. However, that's not what I want to write about. After having read what systemd is capable of, and how it does it, I began to put the existence of all system daemons - in their today's forms - in question.
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RE: Comment by mtzmtulivu
by vivainio on Thu 26th Aug 2010 05:23 UTC in reply to "Comment by mtzmtulivu"
Member since:

What is the problem with the current linux init system that necessitated creation of these two new systems?

It's slow.

Reply Parent Score: 2

RE[2]: Comment by mtzmtulivu
by sorpigal on Thu 26th Aug 2010 16:49 in reply to "RE: Comment by mtzmtulivu"
sorpigal Member since:

If that were the only problem then any one of the init replacements created in the last 15 years would be an improvement.

Speed is secondary. An init replacement primarily needs to solve initialization sequencing. Building an init sequence in which the appropriate things are started at appopriate times, and not before other things that may be needed first, is a highly non-trivial process. Upstart and systemd try to solve this problem and the different approaches define more than anything else the differences between the systems.

After that there are some nice to have things which are lacking on linux. Here I primarily mean service control; it's embarrassing that Windows does this better (yes, better). Both upstart and systemd try to address this in fairly similar ways.

Both (but systemd in particular) do other things, of course, which I consider nonessential but still worthwhile and improvements on current systems. I have to give a great deal of credit to Lennart for not trying to solve just one tiny technical problem but aiming for a holistic approach, while still not greatly violating the *nix philosophy.

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Bill Shooter of Bul Member since:

But init already does the sequencing correctly, in a linear fashion. That's not too difficult at all.

But linear is slow. We have muli core cpu's now. Booting would be faster if we loaded things in parallel. Ok, but what can we load parallel to what, and what has to remain serialized? That's the complexity of the sequencing. its complex due to the parallelization which is due to the need for speed.

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