Re: [gentoo-user] Booting Gentoo from USB stick

[Jake Moe]

On 21/09/10 17:26, J. Roeleveld wrote:
> On Tuesday 21 September 2010 07:35:13 Jake Moe wrote:
>>  On 16/09/10 21:30, J. Roeleveld wrote:
> <snipped old stuff>
>
>>> Please bear in mind, I have not actually used nor needed a ramdisk to
>>> boot from ever since I started using Gentoo.
>>> Not even when I played with booting from USB-sticks myself.
>>> I simply build the kernel with all the necessary drivers compiled-in and
>>> used that to boot from.
>>>
>>> This might also be an idea for you?
>>>
>>> --
>>> Joost
>>>
>>> Eg. if you do the mknod-commands to build the /dev/sda, /dev/sda1,....
>>> device nodes, then it should be able to continue.
>> Well, I've finally gotten this to work with a manually config'ed
>> kernel.  Before, I was only getting kernel panics.  Now, after your
>> comment "all compiled-in", I took the old config I tried, did a sed to
>> change all "=m" to "=y", and recompiled, and it worked.  So obviously,
>> there was some option that I wasn't building into the kernel (only as a
>> module) that was needed to start from USB.
> That's generally a good way to start, stick everything in the kernel :)
>
>> I had previously started from a working config I had previously used for
>> the same model PC that I was doing my testing on, and just changed the
>> USB drivers from modules to built-in, but apparently that's not enough.
>> Any ideas what else is needed for a USB-stick boot that's not needed in
>> a SATA boot?  I'd like to a) find out what I missed, and b) be able to
>> cull the kernel back down again, so I can build up lots of SATA,
>> graphics and audio modules to make this able to boot (and work properly)
>> on other systems.
> Ok, doing this from memory here.
> To be able to boot from USB, you need (additionally to what you normally
> have):
> 1) USB Host drivers (OHCI,UHCI,EHCI,...)
> 2) USB Mass Storage
> 3) file system on the USB-stick
> 4) SCSI-disk (USB Mass storage depends on this)
>
> If others can also have a quick look on this list to check that I didn't miss
> anything?
>
> --
> Joost
>
Well, now that I've managed to get it booting, the only problem is that
I can't seem to get the disk label working right.  In GRUB's menu.lst,
if I use root=LABEL=UsbRoot, it doesn't work (kernel panic, label not
found, but sda1 is listed as available), but if I use root=/dev/sda1, it
works.  However, later in the boot process, it mounts / using
LABEL=UsbRoot in fstab just fine.  Is that a problem with GRUB?  Or the
kernel?  Or am I doing something else wrong?

And for future reference, while looking into various things for this, I
found these in the Gentoo Wiki:
USB Portable Install - http://en.gentoo-wiki.com/wiki/USB_Portable_Install
Portable USB Gentoo - http://en.gentoo-wiki.com/wiki/Portable_USB_Gentoo

Unfortunately, both use genkernel instead of manually configured
kernels, so that part doesn't help, but one mentions the option
"scandelay=2" to add to the kernel boot line in GRUB to introduce the
delay genkernel needed to see the USB device; would have been good to
know that last week when I was trying genkernel.  :-P

Jake Moe