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Old 08-16-2006, 06:35 AM   #1
aroche
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Registered: Apr 2006
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Confusion PLEASE HELP!!!! Initrd + initramfs


I have been trying to get linux to boot by PXE now i have found tons of documents which i am going to get cracking on, but i am getting confused on some things.

1. Initrd in Mandrake 2006 can you mount it ?
2. Initramfs i think i have this one sorted in my head

Anyway i am very confused over the whole initrd setup in linux and i am wondering can someone please explain this to me before i go out of my mind

The below website is where i was reading about mounting the initrd and changing it, now i was trying this on Mandrake 2006 and it fails every time saying that there is no vaild file system found ie Cramfs or ext2 as the document suggest. I'm sure that i am missing something so if someone can point me to a really good doc on this sugject that would be brill

I am also using Kubuntu 6.06 and Mandrake 2006

Thanks a mill

al.

http://kernel-handbook.alioth.debian...initramfs.html
 
Old 08-17-2006, 11:13 PM   #2
blackhole54
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Registered: Mar 2006
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Quote:
Originally Posted by aroche
I have been trying to get linux to boot by PXE now i have found tons of documents which i am going to get cracking on, but i am getting confused on some things.

1. Initrd in Mandrake 2006 can you mount it ?
2. Initramfs i think i have this one sorted in my head

Anyway i am very confused over the whole initrd setup in linux and i am wondering can someone please explain this to me before i go out of my mind
According to the link you provided:

Quote:
The boot process in Debian is a two-stage process, involving the initial RAM filesystem (initramfs for short, sometimes it is also referred to as initrd, which stands for initial RAM disk)
So initramfs and initrd are the same thing. I have always seen it called initrd. This is loaded with the kernel at boot time as the initially mounted filesystem, which allows (among other things) the kernel to have immediate access to driver modules that might be required to access the hard drives. The usual situation is that this gets traded out for a hard disk filesystem later in the booting process, but not always; live CDs like KNOPPIX and embedded systems sometimes leave the original initrd serving as the root of their filesystem.

Traditionally, initrds are compressed (gzip) file systems, although apparently recently Fedora Core has started using cpio. For the traditional ones, you can gunzip them and look at their contents as follows (doing this might be instructive):

Code:
cat initrd.gz | gunzip > initrd.img
mount -o loop initrd.img /mnt/temp
The second command needs to be done as root (Adjust the file names/paths as needed). You can now use your standard tools (such as ls and less, etc.) to look at the filesystem at /mnt/temp. You can also use dumpe2fs (assuming the file system on initrd.img is ext2) to look at the properties of the filesystem as if it were a real partition.

Hope this gets you started.

Last edited by blackhole54; 08-17-2006 at 11:14 PM.
 
Old 08-18-2006, 01:59 PM   #3
soggycornflake
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Registered: May 2006
Location: England
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initramfs and initrd are not the same thing, though they perform the same function. initrd is for 2.4 (though the method still works in 2.6), initramfs is the new, preferred, boot method used in 2.6.

Initrd is a seperate filesystem image that is loaded by the bootloader. Initramfs is a cpio archive that is hard-coded into the kernel image. See <kernel src>/Documentation/early-userspace/README for details.
 
  


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