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Old 08-30-2010, 02:53 PM   #1
BobNutfield
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Upstart vs SysVinit - which is better?


Hello Everyone,

I have been trying to understand how distros like Ubuntu are able to boot and shutdown so quickly while my Slackware takes a full minute to fully boot. It seems that Ubuntu stopped using the SystemV init scripts a good while back and Slackware continues to use them. If I understand it correctly, Upstart runs a number of scripts simultaneously while Slackware runs them one at a time in a predetermine order. I am not complaining about Slackware's boot time because it gives me a better system. I am just trying to understand the differences.

Am I correct about this? My computers are my hobby, not my profession, so it takes me longer to get to understand things.

I would appreciate a comment about whether I am correct about my understanding of this.

Bob
 
Old 08-30-2010, 03:10 PM   #2
pljvaldez
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That's basically true. Upstart and the Debian insserv are what are called dependency based booting. These systems allow simultaneous running of scripts that are not dependent on each other. For example, if package foo depends on package bar, but sshd doesn't depend on bar, then both bar and sshd can be started at the same time. But foo won't start until bar is completely up and running. So that allows multiple things to start up in parallel which decreases boot time. But some things might still take a long time to boot up because they have to wait until package x, y, and z are all started before running "w".

On a side note, Debian's system tries to still be compliant with the linux standard base (LSB) init requirements.
 
Old 08-30-2010, 03:16 PM   #3
BobNutfield
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Thanks, pjvaldez. I was hoping someone who understood this would reply. I also asked because it seems that multiple scripts running at the same time *could* create some issues that would be more difficult to solve if there was a boot failure. Is that correct. or irrelevant?

Bob
 
Old 08-30-2010, 03:34 PM   #4
pljvaldez
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I don't know enough about slackware to know if that would be a problem. But certainly if the packager doesn't properly define the boot dependencies, there could be some trouble. But I would think errors like that would get spit out in your boot log on either system, just like now. I mean, there's nothing stopping me from putting the wrong number in front of a boot dependency right now. I could change the symlink of the networking script to boot last and that would foul up all kinds of stuff on my box...

I pretty much stick with Debian's stable branch and expect stuff like that to be taken care of by the packagers and Debian's excellent QA team. On Slackware, I don't know...
 
Old 08-30-2010, 03:41 PM   #5
BobNutfield
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Thanks again for your reply. My interest in this came about because a poster on the Ubuntu forums wanted to set his system up to boot directly into a command prompt. In Slackware, you would simply edit the /etc/inittab file, but in Ubuntu this file doesn't exist. This poster was guided through a series of rc.X files to get what he wanted. I certainly don't claim to be an expert, but it seemed awful complicated to just be able to boot into a command line by default. I had never tried this in Ubuntu, but I do boot into a command line with Slackware and then startx. I do this because I like to do updates outside of a GUI. Doesn't seem to be easy to do in Ubuntu, but I don't know anything about Debian beyond using Ubuntu.

Thanks again,

Bob
 
Old 08-30-2010, 03:57 PM   #6
pljvaldez
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I believe Debian is going to try to patch upstart to use /etc/inittab still, but I could be mistaken.
 
Old 08-30-2010, 04:15 PM   #7
Richard Cranium
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Quote:
Originally Posted by BobNutfield View Post
Thanks, pjvaldez. I was hoping someone who understood this would reply. I also asked because it seems that multiple scripts running at the same time *could* create some issues that would be more difficult to solve if there was a boot failure. Is that correct. or irrelevant?

Bob
That is correct, although that would normally be an artifact of having a missing dependency.
 
Old 08-30-2010, 04:17 PM   #8
Richard Cranium
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Quote:
Originally Posted by pljvaldez View Post
But certainly if the packager doesn't properly define the boot dependencies, there could be some trouble. But I would think errors like that would get spit out in your boot log on either system, just like now.
Well, the issue would be that some people would see a problem and others would not. A given topological sort of a dependency graph may work even with missing dependencies.
 
Old 08-30-2010, 04:27 PM   #9
BobNutfield
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Quote:
Originally Posted by Richard Cranium View Post
That is correct, although that would normally be an artifact of having a missing dependency.
I understand. Is this type of boot script system unique to Debian and it's derivatives or do other distros use something other than SystemV scripts?

Thanks

Bob
 
Old 08-30-2010, 05:08 PM   #10
GazL
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I believe Upstart was a Canonical project that was inspired by Apple's 'launchd'. (That's from memory, so I might not be entirely accurate).

Slackware's init system is more of a hybrid between BSD and SysV init styles. The actual SysV stuff are the rc3.d and init.d directories, which slackware supports but doesn't actually make use of itself.

Personally, I don't like event driven automation. I've worked on systems that have been based on that sort of design in the past and when thing go wrong they're nothing but trouble. I'll happily trade the 10-20 seconds I might gain from using a event driven boot sequence for a a well defined, reliable and predictable chain of events.


Oh, for what it's worth OpenSUSE 11.3 has an option in yast to choose between a traditional init and an upstart one.

Last edited by GazL; 08-30-2010 at 05:10 PM.
 
Old 08-30-2010, 05:37 PM   #11
Richard Cranium
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Quote:
Originally Posted by BobNutfield View Post
I understand. Is this type of boot script system unique to Debian and it's derivatives or do other distros use something other than SystemV scripts?

Thanks

Bob
I believe that Gentoo uses something similar to Upstart, but not the same.

You may find this interesting: http://www.safe-mbox.com/~rgooch/lin...pts/index.html
 
  


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