FreeBSD Boot Times

[Mark Saad]

On Jun 11, 2012, at 6:21 PM, Brandon Falk <bfalk_bsd at brandonfa.lk> wrote:

> Greetings,
> 
> I was just wondering what it is that FreeBSD does that makes it take so long to boot. Booting into Ubuntu minimal or my own custom Linux distro, literally takes 0.5-2 seconds to boot up to shell, where FreeBSD takes about 10-20 seconds. I'm not sure if anything could be parallelized in the boot process, but Linux somehow manages to do it. The Ubuntu install I do pretty much consists of a shell and developers tools, but it still has a generic kernel. There must be some sort of polling done in the FreeBSD boot process that could be parallelized or eliminated.
> 
> Anyone have any suggestions?
> 
> Note: This isn't really an issue, moreso a curiosity.
> 
> -Brandon
> _____________________________________________

In amd64 builds the system checks it's ram twice . Early in the boot phase using a slower method , and latter using a faster SMAP method. In 9.0-RELEASE you can disable the early men check via a loader tunable ,  here is a snip it from the release notes on 9.0 . It should also be mfc'd to 7, and 8 stable. 

[amd64, i386, pc98] A loader(8) tunable hw.memtest.tests has been added. This controls whether to perform memory testing at boot time or not. The default value is 1 (perform a memory test).[r224516]

The next it is switch to a modular kernel  this speeds up boot times be omitting kernel items you do not need, you can also do this via with a static kernel by removing / disabling unused options . Look at the Archives for ha hackers there is a ton of info on this. 

Most of the rest of the boot up time is  via init / rc'ng starting an configuring things . Right now this is not parallel-ized out the box . Pc-bsd has something called fastboot ? I am am not sure how it works but it improves load time in their setups . See http://lists.pcbsd.org/pipermail/testing/2012-January/006358.html

Other then that, there  are some other things being developed check the FreeBSD wiki for a rc.ng management daemon frs or fsr ? 

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Mark saad | mark.saad at longcount.org