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#1 2013-04-07 22:00:02

abefar
Member
Registered: 2010-04-28
Posts: 6

udev in initramfs or not?

Greetings!

I recently started using an initramfs due to moving my root filesystem to a RAID-1 array with 1.2 metadata. I have been using the following hooks until now:

HOOKS="base autodetect fsck mdadm"

However, I noticed that a few guides recommends using mdadm_udev instead of mdadm. That, however, requires adding the udev hook as well.
I switched to that configuration at the last kernel upgrade, but I don't notice any difference, except for a considerably larger initramfs image.

What exactly is the advantage of having udev in your init filesystem? Will the plain old mdadm hook become obsolete in the future?

Thanks.

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#2 2013-04-14 11:55:47

teateawhy
Member
From: GER
Registered: 2012-03-05
Posts: 1,058
Website

Re: udev in initramfs or not?

You can read the help page to these hooks if you want to know more.
$ 'mkinitcpio -H mdadm'
$ 'mkinitcpio -H mdadm_udev'

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#3 2013-04-14 20:54:54

jacobopantoja
Member
From: Madrid
Registered: 2011-03-16
Posts: 44

Re: udev in initramfs or not?

abefar wrote:

I recently started using an initramfs due to moving my root filesystem to a RAID-1 array with 1.2 metadata.

What were you using before? A custom-compiled kernel? If not, I cannot grasp how could you boot without initramfs.

As far as I know udev is the preferred method to load the modules, so I don't see a problem in using it. What is exactly your concern?

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#4 2013-04-15 13:07:21

falconindy
Developer
From: New York, USA
Registered: 2009-10-22
Posts: 4,095
Website

Re: udev in initramfs or not?

abefar wrote:

What exactly is the advantage of having udev in your init filesystem?

Using udev means you don't have to worry about knowing exactly which modules to load, and you can effectively wait on devices which might take a while to show up (as you can expect symlinks like /dev/disk/by-*/* to be created asynchronously by udevd). I'm not sure why you're concerned about your initramfs image size -- udev really doesn't add that much weight.

abefar wrote:

Will the plain old mdadm hook become obsolete in the future?

Yes, it will. mdadm will soon™ be what mdadm_udev is now, with the latter being deprecated.

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#5 2013-10-16 09:36:56

donniezazen
Member
From: Salt Lake City
Registered: 2011-06-24
Posts: 671
Website

Re: udev in initramfs or not?

What happens to via-udev hooks when systemd hook fully replaces udev? I don't use base or udev. I only use systemd hook.

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#6 2013-10-20 14:17:37

falconindy
Developer
From: New York, USA
Registered: 2009-10-22
Posts: 4,095
Website

Re: udev in initramfs or not?

donniezazen wrote:

What happens to via-udev hooks when systemd hook fully replaces udev? I don't use base or udev. I only use systemd hook.

Then you're using udev.

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