[gentoo-amd64] initrd

[gentoo-amd64] initrd

[DR GM SEDDON]

Dear list,
I have just started using Gentoo and up-to-now am impressed.  I have 
generated a kernel using 'genkernel' and the kernel is in /boot.  
However, I do not have 'initrd' but 'initramfs'.  is this a problem or 
should I modify grub appropriately?
Gavin.
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Re: [gentoo-amd64] initrd

[Mark Knecht]

On 10/28/05, DR GM SEDDON <gavin.m.seddon@manchester.ac.uk> wrote:
> Dear list,
> I have just started using Gentoo and up-to-now am impressed.  I have
> generated a kernel using 'genkernel' and the kernel is in /boot.
> However, I do not have 'initrd' but 'initramfs'.  is this a problem or
> should I modify grub appropriately?
> Gavin.

Possibly. I don't use an initrd at all and boot just fine, so it's
possible that you can skip the whole issue if you want to.

Cheers,
Mark

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[gentoo-amd64] Re: initrd

[Duncan]

Mark Knecht posted
<5bdc1c8b0510280754u28830e2bwa2b9fadba6b66a35@mail.gmail.com>, excerpted
below,  on Fri, 28 Oct 2005 07:54:17 -0700:

> On 10/28/05, DR GM SEDDON <gavin.m.seddon@manchester.ac.uk> wrote:
>> Dear list,
>> I have just started using Gentoo and up-to-now am impressed.  I have
>> generated a kernel using 'genkernel' and the kernel is in /boot.
>> However, I do not have 'initrd' but 'initramfs'.  is this a problem or
>> should I modify grub appropriately?
>> Gavin.
> 
> Possibly. I don't use an initrd at all and boot just fine, so it's
> possible that you can skip the whole issue if you want to.

initrd/initramfs isn't normally needed for boot sequences where the kernel
has the drivers required to mount / builtin.  It's there, for cases such
as / on RAID, where some initial setup is required before the normal /
partition can be loaded.

Another case where initrd/initramfs is used, is for mainly binary
distributions, where all the various file system and disk drive interface
chipset drivers are compiled as kernel modules, rather than built-in. 
Obviously, if a module needed to load / is stored in /lib/modules on the /
partition, it won't be reachable, thus an initrd (the old solution) or
initramfs (the newer one) is configured, containing the modules and
configuration needed to mount the normal /.  (I say normal /, because an
initrd/initramfs functions as a temporary / file system while these things
are loaded, then a pivot_root is used to transfer to the normal /
partition, once it is mounted.)

Gentoo's genkernel creates an initrd/initramfs because it bases its
initial configuration on that of the liveCD, after the LiveCD has detected
your hardware and loaded the appropriate modules.  The LiveCD uses an
initrd so it can load modules as necessary, and also so it can pivot-root
off of the read-only temporary CD root, to a read/write ramdisk root
created and loaded with the necessary goodies uncompressed off the CD. 
Because genkernel bases its default setup on the one off the CD, it too
defaults to an initrd/initramfs, even tho most folks don't actually need
one, once they have a kernel with the drivers necessary to mount root
compiled in.

So, answering the original question, initramfs is the new version of
initrd, so no, you don't have to worry about it.  However, chances are,
unless you are running your / on RAID or something similarly exotic, you
don't need an initramfs either, if you have at minimum, the drivers
necessary to mount your / filesystem, compiled directly into the kernel,
not as modules.

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman in
http://www.linuxdevcenter.com/pub/a/linux/2004/12/22/rms_interview.html


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Re: [gentoo-amd64] initrd

[Hemmann, Volker Armin]

On Friday 28 October 2005 16:13, DR GM SEDDON wrote:
> Dear list,
> I have just started using Gentoo and up-to-now am impressed.  I have
> generated a kernel using 'genkernel' and the kernel is in /boot.
> However, I do not have 'initrd' but 'initramfs'.  is this a problem or
> should I modify grub appropriately?
> Gavin.

I touched genkernel only once (when a friend used it, and it made a totally 
useless kernel) and from my experience it builds inadequate kernels.
Plus, if you are not using raid, any initrd/initramfs just adds time and 
overhead to your booting. It is a waste of ressources.
The only ones who 'need' it are distributions, who do want to use a 'one 
kernel fits all' approach and people with / on a raid/dm device.

Just build a kernel by yourself. It is easy.
make menuconfig
mount /boot
make all modules_install install 
and let grub.conf point to vmlinuz and vmlinuz.old.

The install run will create a vmlinuz link to your latest kernel and a 
vmlinuz.old link to the one used.
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