Re: [gentoo-amd64] boot Gentoo from USB key

[Raffaele BELARDI]

Thanks to you and Kyle for the hint on rootdelay, I will give it a try.

Regarding the performance, it should not be a real issue in my case. I
will only use the key to boot the kernel and send a Wake-on-Lan packet
to a file server, then I'll mount the discs over NFS.

bye,

raf

On Wed, 2008-04-30 at 08:56 +0200, Branko Badrljica wrote:
> I had the same two problems.
>
> WRT to grub, I don't remember anymore exactly what I have done, but I
> think I have
> copied sectors 1-62 from one conventional grub-bootable HDD to USB,
>
> Or maybe used some old HDD and formated it, parittioned it like the USB
> disk, copied /boot partition on it and set up grub on it, then copied
> sectors 1-62 back to USB disk.
> Sector 0 is for MBR codeand last few tens of bytes contain headers for
> first 4 partitions, so it shouldn't be touched and first partition
> begins with sector 63.
>
> Something like that.
>
>
> WRT to boot panics, kernel can't find USB key at boot since USB
> initialisation code needs more time for key to stabilise. Use kernel
> parameter rootdelay=10 for 10 second wait period for USB
>
> Hope this helps.
>
>
> BTW: You will in all likelyhood be dissapointed with USB key
> performance. Its R/W throughput is comparable to HDD only on paper. In
> reality it seems that USB can't cope efficiently with small sector-sized
> writes but also scattered reads seem to be far from optimal.Either that
> or USB driver really sucks on Linux.
>
> It is very useable as fallback though. Like having one USB key soldered
> directly on the MoBO and using it for boot if/when your HDD croaks or if
> something eats your main boot option...
>
>
> Regards,
>
>
> Branko
>
>
>
>
> Raffaele BELARDI wrote:
> > In the process of building an amd64 diskless box, I am trying to make a
> > bootable USB key with no success up to now.
> >
> > The first problem I encountered was related to ext2/vfat. I initially
> > tried to format the key as ext2, but grub refuses to install on it. Even
> > though I copied the /boot/grub/* directory into the key, and I see it is
> > there, grub does not see it. The problem does not happen with vfat.
> >
> > So I worked around that and created two partitions in the key, a small
> > vfat for the /boot and a 2Gb ext2 for the /. I copied the stage3 into
> > the / with no problem. In the /boot I put the kernel image which I am
> > already using on the same box, for now with discs still connected. All
> > the modules are compiled in.
> >
> > When I boot from the key, grub enters the shell (although I did create
> > the grub.conf and menu.1st, so I don't understand why it doesn't show
> > the menu). I manually specify the kernel file location and root
> > parameter:
> >
> >
> >> kernel /linux-2.6.24-gentoo-r4 root=/dev/sdg1
> >> boot
> >>
> >
> > The kernel starts to load, but panics because it is unable to find the
> > root partition. When it stops it shows the available partitions, these
> > include all the hard disk partitions but no USB key partition. In fact,
> > if I omit the 'root' parameter from the grub shell the boot works fine
> > but it uses the hard disk root partition instead of the USB one.
> >
> > >From the log on the screen the USB controller seems correctly detected,
> > so I don't understand why it is not finding the root. While writing this
> > one idea comes to my mind, maybe it is failing because I attach the key
> > to a SDC/MMC/USB card reader? This evening I'll try to plug it into a
> > different USB slot.
> >
> > Any other ideas welcome.
> >
> > raffaele
> >
> >
>

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