merging kernel and root fs into one image

nareshn.87 · 06-05-2007, 03:16 AM

hey,
I am using an ARM mup with a montavista distro with the kernel and rfs on a compact flash. The kernel accesses the rfs from the flash each time which slows down boot up and operation. Can u please tell me how to combine the kernel and rfs into one image so that the rfs is always residing in memory and hence working faster?..
thanks..
naresh

MS3FGX · 06-05-2007, 07:46 AM

Are you saying that the system is actually installed to the CF, or that the CF card is holding the kernel and initrd file?

I think what you want to be doing is using an initrd file on the card, but it sounds like you have the system just installed directly onto a partition of the card. Is that correct?

thegeekster · 06-05-2007, 08:36 AM

What you're looking for is pretty common with some livecds or pendrive installations......

The general procedure is to have a kernel with enough drivers built in and/or have modules on an initial ramdisk (initrd) which is loaded in memory, along with the kernel, for the bootup process.......At the end of the boot process, the kernel looks for a file, usually called linuxrc, which then has instructions to replace the initrd with a compressed root filesystem..........The root filesystem can be loaded in memory, but it depends on the instructions contained in linuxrc on how this is accomplished.......There are a few different ways to accomplish this......This works well with embedded systems, of which quite a few use an ARM architecture, among others......

Here's a Wikipedia page explaining about initrd, and the boot up process.....This should give you an introduction, to start with.....

HTH

---thegeekster

nareshn.87 · 06-06-2007, 01:56 AM

Quote:

Originally Posted by MS3FGX

Are you saying that the system is actually installed to the CF, or that the CF card is holding the kernel and initrd file?

hey..i don get what u mean by installed to the cf?..i mean jus present as two images for initrd and the kernel on the flash..

nareshn.87 · 06-06-2007, 02:01 AM

Quote:

Originally Posted by thegeekster

The general procedure is to have a kernel with enough drivers built in and/or have modules on an initial ramdisk (initrd) which is loaded in memory, along with the kernel, for the bootup process.......At the end of the boot process, the kernel looks for a file, usually called linuxrc, which then has instructions to replace the initrd with a compressed root filesystem..........The root filesystem can be loaded in memory, but it depends on the instructions contained in linuxrc on how this is accomplished.......There are a few different ways to accomplish this......This works well with embedded systems, of which quite a few use an ARM architecture, among others......

---thegeekster

hey..thank god i finally found someone who knows what i'm talkin about..i've tried looking everywhere but everyone just seems to mention that it is 'possible' to load the root file system into memory by merging the kernel and the rfs into one image so that the rfs always resides in memory. How exactly is this done?..i need info both on how to load the rfs onto memory ( which im guessing is by modifying the linuxrc file) and how to combine the kernel and the initial rfs into one image..
It'll be great if u could help me!!
thanks a lot
naresh