I just want to thank everyone for all your explanations -- it's been very helpful! Moving on to newer problems now, but it's always great to have things explained to you! matt
On Fri, Jan 31, 2003 at 05:34:59PM -0600, Shyamal Prasad wrote: > "Matt" == Matt Price <[EMAIL PROTECTED]> writes: > > Matt> hi there, can someone help me figure out what exactly initrd > Matt> is, and why kernels use it? I have looked through the docs, > Matt> and I understand that it's thefile used for an initial > Matt> ramdisk in some cases, but I don't understand why it would > Matt> be used in some cases and not in others. So for inst ance, > Matt> the demudi kernel I just installed seems to demand the use > Matt> of initrd, and I take it GRUB needs an anitrd argument to > Matt> load the kernel. But why don't my own self-compiled kernels > Matt> require an initrd argument at boot (nor have an initrd file > Matt> anywhere in /boot, as far as I can tell)? > > I'm not expert on this, but here goes anyway: the initrd image is, > like you point out, a ramdisk image that common Linux bootloaders > (lilo, grub, ....) can load off a wide variety of file systems. > > There is no real need to use initrd for personal use. If you know > exactly what you need in your kernel, just build it in. (well, > personally, I never build a kernel unless my hardware requires it, the > pre-packaged Debian kernels are wonderful bits of art :-) > > Initrd gets to be very useful when you try to build a kernel that will > be used in a wide variety of environments. You don't want to build > everything into the kernel, but at the same time you are not sure what > might be required to boot a system up and find the rest of the system. > > In that case you build a small kernel with what you know everyone will > absolutely need. Then you throw a lot of stuff that will satisfy a > large variety of systems into the intird image. The initrd ram disk is > used to bootstrap the kernel: basically you boot the kernel, mout the > initrd image, which pokes around and loads modules it figures that > specific system needs to find the rest of the hardware (e.g. it needs > ext3 or rieserfs file system support for the root partition or some > such thing), then mounts the root file system and goes on with the > usual initialization. > > The advantage is of this approach is, for example, that if you don't > use ext3 you will not find ext3 in your memory. But if you use ext3 > you can still boot the system even though ext3 is not built into the > kernel (because it is in the initrd image). > > You can use 'mount -t cramfs -o loop /mnt intrd.img.file.path' to look > into an initrd image. You will find it quite instructive I'm sure. > > Cheers! > Shyamal > > > -- > To UNSUBSCRIBE, email to [EMAIL PROTECTED] > with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED] -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
