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Old 08-20-2004, 09:36 AM   #1
abs
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must use initrd if compiled into kernel?


hi
i added all ram disk sections into the kernel (compiled in). i just wanted to verify, it's still optional to use initrd with that, right or is it required to use if compiled in? i'd expect it to be optional but having trouble booting my 2.6.x kernel.

ty
abs
 
Old 08-20-2004, 09:59 AM   #2
masand
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hi
initrd is required to load the initial part of the system
i.e before all the services start ,

u need to build the initrd by the
'mkinitrd' command
after u have compiled ur kernel
regards
gaurav
 
Old 08-20-2004, 01:11 PM   #3
abs
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yeah i know.

my question was, IF i compile initrd into the kernel, do i HAVE to use it? trying 2.6.8.1

(my 2.4.26 kernel boots without an initrd)
 
Old 08-20-2004, 02:00 PM   #4
masand
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hi
yes
whaty i think is that if u compile initrd into kernel,that means u r compiling ur kernl for initrd support
so i think u need initrd.

also do u have any reasons for not using initrd

regards
gaurav
 
Old 08-21-2004, 12:38 AM   #5
Shade
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Why use initrd if there's no reason?
I never understood why RedHat, Mandrake, SuSE all use them but my favorite slackware doesn't...

Can someone explain what its usefulness is?

--Shade
 
Old 08-21-2004, 01:55 AM   #6
Cedrik
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For my part I used to compile initrd feature (virtual ram disk etc) in kernel, but I never used it yet (no reason for that). The kernel boot fine without initrd although feature is compiled as built-in (2.6.7 kernel), so if you have problem to boot it, I think the error does not come from initrd.

I think RedHat, Mandrake, SuSE do initrd for load many modules at boot to detect a maximum various hardware and filesystem without compile all in the kernel as built-in (to reduce kernel file size), If you look at redhat .config file for kernel, nearly all the features are enabled (maybe to obtain a sort of plug and play system, I don't know)
 
Old 08-21-2004, 04:23 AM   #7
nukkel
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Yes, those distros prefer to build nearly everything as modules; what you need to put inside the initrd are just those modules that are neccesary to be able to mount the root filesystem (eg. ext3, or scsi card drivers).

Because, imagine you need to load the driver for your scsi card, in order to mount the root fs... but that module is in /lib/modules, *ON* your root fs, which is not mounted yet --> deadlock!
 
Old 08-21-2004, 06:14 PM   #8
abs
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my reply:
http://www.linuxquestions.org/questi...18#post1124418
(both threads related to issue)

conclusion: even if initrd is compiled in, it's not necessary to use. check out the other thread.

ty
 
Old 08-23-2004, 12:14 AM   #9
gnashley
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You don't have to use it just because it's compiled in-. Have a study at rdev to see where you may have problems though.
initrds are great, try running a slack install without one!
Where slackware provides pre-compiled kernels for unusual hardware support the other distros will provide an initrd that lets you load a module from a floppy during boot-up. Then, when installed you create a custom initrd to install your needed modules. this ability is needed for 2.6.x because of kernel size, which limits the ability to include compiled-in support.
 
Old 08-23-2004, 12:26 AM   #10
masand
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hi
what i think is that initrds are used only during startup
they are of no use afterwards
so compiling then in the kernel and getting kernel bigger ,doesn't it decrease the performance with the case where we do not have the initrd along with the kernel

regards

gaurav
 
Old 08-23-2004, 01:28 PM   #11
abs
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Quote:
Originally posted by masand
so compiling then in the kernel and getting kernel bigger ,doesn't it decrease the performance with the case where we do not have the initrd along with the kernel
it might make it slightly bigger but i don't think it decreases performance on the kind of machines there are. i don't mean the high end ones. i doubt it'd make a big diff even on a 120/133 MHz. it might just take up more space in ram.

on the other hand, things like unneccesary device drivers and debugging capability compiled into the kernel is the cause of significant performance hit. debugging is not bad, but if u don't use it, u're *not* using an active kernel feature.
 
  


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