How to disable udev for a faster boot?

[whitehead1415]

I am trying to make gentoo boot faster and in my searching I came across this article http://lwn.net/Articles/299483/. One of the things they did was revert to a "persistent, old-school /dev directory so that boot doesn't depend on udev". I would like to know how to do this, but when I searched for disabling udev all the forums say that its a bad idea. All I want to know is how to make a static /dev directory. If someone could tell me how to do this or even just point me in the right direction I would really[/quote] appreciate it.

[cach0rr0]

Had a brief discussion on that in this thread - https://forums.gentoo.org/viewtopic-t-402844-highlight-devtmpfs.html

In terms of speeding up boot time, the biggest bang for your buck would be making the move to baselayout-2/openrc

It alone took my laptop from booting in around a minute, to 34 seconds (I'm now down to 26s with other tweaks)

If you care to experiment as well, check /etc/conf.d/rc

I don't know if this is specific to baselayout-2/openrc, or if it's available on baselayout-1 as well, but I did find these two options:

[honp]

I think that you have to allow devfs in kernel(if it is still possible) and then you need something that create all the needed devices in /dev.

[cach0rr0]

[honp]

Nono, devtmpfs is not what i thought. I tried to find devfs in 2.6.31 kernel but i didn`t find it. Probably it is too old:(

[cach0rr0]

[Mike Hunt]

Linux 2.3.46pre5 – 2.6.17 devfs /dev
Implemented fully in the kernel. DEPRECATED: Users are encouraged to migrate to udev.

[whitehead1415]

Thanks for the advice. The reason why I wanted a static /dev was because I tried to use the finit-arc but I think because arch linux uses bsd style init the scripts like udev and hal didn't start. I tried to modify everything needed for boot to be like the arch linux for example the rc.conf, and I got everything working like loading modules but I couldn't figure out how to start the services. The only thing I really needed to load was udev but I figured it would be easier to just use a static /dev. So I put a line in the finittab to cp a saved /dev directory to /dev and everything was working except for my wireless card which couldn't find the firmware for some weird reason. Anyway I booted into x in 7 seconds but there is still a few things that don't work like terminals couldn't access the psuedo-ptty even though it worked for root and the permissions were set right. so I think that I will just revert back to the old boot and experiment more with openrc, readahead, and making my kernel load faster.

If there is anyone out there that knows how to make the finit-arc work in gentoo, or even how to get another fast-init/finit type of init to work in gentoo please let me know. I think the best for gentoo is probably something like einit, mininit, or initng. At least those are the ones I found in portage, I will be testing these out also. Maybe if I can learn enough about it I will just write my own init.

As a side note I understood devfs to be an attempt at making a dynamic /dev but it didn't work out so well and it was replaced by udev. I think the static /dev was before devfs, and devfs wasn't added until the 2.3-2.4 kernel

[cach0rr0]

so having read through this thread:

http://lkml.indiana.edu/hypermail/linux/kernel/0909.2/00785.html

Seems the suggestion that devtmpfs would provide an improvement in boot time is completely false under most if not all circumstances.
As well they concede that saying boot speed as a selling point is flat wrong, as well that it's completely unnecessary if you call udev early during init

So it would seem I'm wasting my time trying to leverage this to get my boot time down from 20s into the teens

I could roll a static dev, but thus far my efforts have been epic fail since I'm using lvm.
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