Question on the microcore Linux kernel

[lid]

Hi,

I was able to pxeboot the microcore using vmlinuz as kernel and core.gz as initrd.
As far as I can see, the kernel is

tc@box:~$ uname -a
Linux box 3.0.21-tinycore #3021 SMP Sat Feb 18 11:54:11 EET 2012 i686 GNU/Linux
tc@box:~$

The questions are:

1. Is this the stock Linux kernel 3.0? Or has it been modified?
2. If it has been modified, where can I find the diff?

Thanks.

David

[genec]

1. Is this the stock Linux kernel 3.0? Or has it been modified?
2. If it has been modified, where can I find the diff?

1) Yes.  2) with the other source files.

[Rich]

Hi lid
Check here:
http://distro.ibiblio.org/tinycorelinux/4.x/x86/release/src/kernel/

[lid]

Hi lid
Check here:
http://distro.ibiblio.org/tinycorelinux/4.x/x86/release/src/kernel/

I got the linux-3.0.21-patched.txz. How do I find out about the diff from the stock kernel? Should I just run diff against stock 3.0.21? Or is there any document that describes the changes.

[tinypoodle]

See the patches subdir there

[lid]

See the patches subdir there

OK, got it.

I am trying to understand the magic why microcore can be booted up entirely in RAM. My kernel knowledge is limited. It seems to me that the tmpfs-root.patch is the key. This patch lets the ramfs to be used as root fs. Is this correct?

What I still dont' understand is how kernel knows to use ramfs on boot? In my pxeboot, the bootloader only has the following line:

   APPEND initrd=tinycore/core.gz

It's not obvious to me that how the kernel determined to boot everything into RAM.
Can someone give me more pointers or explain a little bit more?

David

[gerald_clark]

initrd stands for initial ramdisk.
Linux boots into RAM.
With most distros, the initrd mounts a new root file system and then switches to it.
Core skips this step, and continues to run in RAM.

[curaga]

For background, see Core Concepts, and the Distrowatch interview from a couple years back.

http://distrowatch.com/weekly.php?issue=20090323

[lid]

initrd stands for initial ramdisk.
Linux boots into RAM.
With most distros, the initrd mounts a new root file system and then switches to it.
Core skips this step, and continues to run in RAM.

I want to play with it. Should I use config-3.0.21-tinycore as .config to recompile the kernel as 32 bit? If so, should I copy config-3.0.21-tinycore to .config and do a make oldconfig?

Thanks.

[curaga]

Yes, that works.

[lid]

initrd stands for initial ramdisk.
Linux boots into RAM.
With most distros, the initrd mounts a new root file system and then switches to it.
Core skips this step, and continues to run in RAM.

A follow up question: Can a stock kernel also bypass mounting the root fs and directly boot into ram? Can this be done just by using kernel boot options like root=/dev/ram0?

[gerald_clark]

Without telling the bootloader to load the initrd. there is no RAM filesystem to mount.
There is nothing particularly unique about Core's kernel.

[lid]

Without telling the bootloader to load the initrd. there is no RAM filesystem to mount.
There is nothing particularly unique about Core's kernel.

I mean how about "initrd=core.gz root=/dev/ram0". Will this work with a stock kernel to boot into ram?

[gerald_clark]

Go back and reread reply #6.

[tinypoodle]

The links under chapter "initramfs" here:
http://www.landley.net/writing/
should pretty much cover the whole subject.

To me it looks like the patch is replacing ramfs with tmpfs, though from what I had read I had always understood that tmpfs could be enabled without a patch, so I am not really sure about that.