Re: [gentoo-user] Re: gentoo livedvd kernel

[Rich Freeman]

On Wed, Nov 12, 2014 at 1:50 PM, Neil Bothwick <neil@××××××××××.uk> wrote:
> On Wed, 12 Nov 2014 18:31:07 +0000 (UTC), James wrote:
>
>> > 1) Boot from the DVD and copy /proc/config.gz to a
>> > writeable device.
>>
>> cool, this gets me the .config file.
>>
>> > 2) Copy the kernel from the DVD and use
>> >    /usr/src/linux/scripts/extract-ikconfig to extract the config.
>>
>> Ok, I'm not sure where the actual kernel binary is on the livedvd.
>> I really want that actual binary.
>
> I thought you just wanted the config. If you look in the bootloader menu,
> either from the menu itself or at its config file on the disc, you will
> see the path to the kernel it is using.
>
> If the live DVD uses GRUB, the config is at grub.cfg as usual. If it uses
> isolinux it will be either /isolinux/isolinux.cfg or
> /boot/isolinux.isolinux.cfg.
>

Generally the kernel is the easiest thing to get off of one of those
LiveDVDs by just sticking the DVD in a drive and reading it (without
booting it).  Everything else on the DVD except for the kernel and
initramfs and bootloader tends to go in some big squashfs or the like.
However, the kernel has to be someplace the bootloader can read it,
and that usually means a vmlinuz or whatever on the root directory.

You could probably just use the same kernel on your own system, unless
it has an embedded command line or initramfs (I forget offhand how
overriding either of these works).  Most bootloaders tend to not
require these, but in some embedded situations you could run into
them.  Once upon a time the kernel had a BIOS boot sector in the first
512 bytes so you could just dd the kernel onto a disk and boot it
(there is still a stub that will tell you to bugger_off_msg if you do
that in arch/x86/boot/header.S).  (just a bit of trivial there)

--
Rich