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

[Jake Moe]

On 15/09/10 04:28, YoYo Siska wrote:
> On Fri, Sep 10, 2010 at 07:29:01AM -0400, David Relson wrote:
>> On Fri, 10 Sep 2010 11:05:12 +0200
>> J. Roeleveld wrote:
>>
>>> On Friday 10 September 2010 10:43:30 Jake Moe wrote:
>>>>    On 10/09/2010 5:27 PM, Maciej Grela wrote:
>>>>> 2010/9/10 Jake Moe<jakesaddress@×××××.com>:
>>>>>>    Hello all,
>>>>>>
>>>>>> I've been thinking about creating a Gentoo USB stick for install
>>>>>> and rescue purposes (and, of course, just to see if I could).
>>>>>> I've mostly followed the Gentoo handbook (I used a single 4GB
>>>>>> partition for the whole system, and no swap).  I've used
>>>>>> genkernel for the kernel (so I can have a multi-system capable
>>>>>> kernel).  I've gotten GRUB installed and working.  My problem
>>>>>> comes in after what I believe is the init process:
>>>>>>
>>>>>>
>>>>>> Gentoo Linux; http://www.gentoo.org
>>>>>>
>>>>>>    Copyright 1999-2009 Gentoo Foundation; Distributed under the
>>>>>> GPLv2
>>>>>>
>>>>>> Press I to enter interactive boot mode
>>>>>>
>>>>>>    * Mounting proc
>>>>>> at /proc ... [
>>>>>>
>>>>>> ok ]
>>>>>>
>>>>>>    * Mounting sysfs
>>>>>> at /sys ... [
>>>>>>
>>>>>> ok ]
>>>>>>
>>>>>>    *
>>>>>> Mounting /dev ... [
>>>>>>
>>>>>> ok ]
>>>>>>
>>>>>>    * Starting
>>>>>> udevd ... [
>>>>>>
>>>>>> ok ]
>>>>>>
>>>>>>    * Populating /dev with existing devices through
>>>>>> uevents ... [
>>>>>>
>>>>>> ok ]
>>>>>>
>>>>>>    * Waiting for uevents to be
>>>>>> processed ... [
>>>>>>
>>>>>> ok ]
>>>>>>
>>>>>>    * Mounting devpts
>>>>>> at /dev/pts ... [
>>>>>>
>>>>>> ok ]
>>>>>>
>>>>>>    * Checking root filesystem ...
>>>>>>
>>>>>> fsck.ext2: No such file or directory while trying to
>>>>>> open /dev/sda1 /dev/sda1:
>>>>>> The superblock could not be read or does not describe a correct
>>>>>> ext2 filesystem.  If the device is valid and it really contains
>>>>>> an ext2 filesystem (and not swap or ufs or something else), then
>>>>>> the superblock
>>>>>>
>>>>>> is corrupt, and you might try running e2fsck with an alternate
>>> superblock:
>>>>>>      e2fsck -b 8193<device>
>>>>>>
>>>>>>    * Filesystem couldn't be
>>>>>> fixed :( [
>>>>>>
>>>>>> !! ]
>>>>>> Give root password for maintenance
>>>>>> (or type Control-D to continue):
>>>>>>
>>>>>>
>>>>>> If I give the root password, I can find no /dev/sda1.  However,
>>>>>> mount shows /dev/sda1 on /, and there *is* a /sys/block/sda
>>>>>> folders, with a sda1 folder in that as well.  It's almost like
>>>>>> it had /dev/sda1, but then lost it somehow.
>>>>>>
>>>>>> Does anyone have any idea what's going on here?  Any help would
>>>>>> be appreciated.
>>>>> Have you seen http://www.sysresccd.org/Main_Page ? It's based on
>>>>> Gentoo, you could check what they did to boot from a usb stick.
>>>>>
>>>>> Br,
>>>>> Maciej Grela
>>>> Excellent, thanks for that, I hadn't found it in my previous
>>>> searches. I'll have a look there.
>>>>
>>>> Jake Moe
>>> Had a similar issue a while ago when I was playing around with this
>>> myself.
>>>
>>> Take a look at the linux boot parameters.
>>>
>>> The 'theoretical' part is: You need to let the kernel initialize the
>>> USB-stick before trying to access it. (This can take some time)
>>>
>>> There is a delay-option, just can't remember the proper name off-hand.
>>>
>>> --
>>> Joost
>> I've got USB booting working in a syslinux environment.  A delay of 12
>> seconds is working for me.  The syslinux.cfg stanza I use is:
>>
>> LABEL usb
>> KERNEL linux
>> APPEND rootdelay=12 root=/dev/sda2
> The usual way for linux on removable usb sticks / disks is to use LABEL
> or UUID to identify the disks and not the device names, because they
> will be different in different computers ;) The downside is that you
> need an initrd to mount the root partition... I think that the usual
> initrd generated by genkernel works...
>
> If you created the rootfs with:
> mkfs.ext2 -j -LUSBGentoo  /dev/sdXY
>
> then you can change the kernel parameter to
> root=LABEL=USBGentoo
>
> and your fstab to:
> LABEL=USBGentoo		/		ext3 ...
>
> You can also use the uuid of the filesystem, find it out with
> dumpe2fs -h  /dev/sdb2 | grep UUID
> and then use UUID=XXX instead of LABEL=XXX
>
> I never really played around with grub and  USB booting, so I use
> syslinux. I create a small FAT partition with syslinux, kernel and
> initrd image  (it gets also pretty handy when you sometimes need to copy
> something from a windows machine ;) and a second "regular" ext3
> partition for the rootfs.
>
> Basically you would do:
> - partition the stick, mark the FAT partition as bootable/active
> - format the partitions:
>    - mkfs.vfat -nUSBData /dev/sdX1
>    - mkfs.ext2 -j -LUSBGentoo /dev/sdX2
> - install syslinux (on the FAT partition):
>    - syslinux /dev/sdX1
> - mount /dev/sdX2, install gentoo in the usual way
> - compile the kernel and initrd, make sure required USB stuff is in the kernel
>     (theoretically it could be as modules in initrd... but in-kernel is safer :)
>    if you are in a hurry, or don't know how to create them, get them from
>    a gentoo livecd ;) don't forget to also copy the modules
>    (/lib/modules-XXX/...) from the livecd to the rootfs.
> - put the kernel and initrd on the FAT partition (I name them  vmlinuz.img
>    and initrd.img)
> - edit syslinux.cfg (on the FAT partition), see
>    http://syslinux.zytor.com/wiki/index.php/SYSLINUX#How_do_I_Configure_SYSLINUX.3F
>    a very simple one from my USB disk:
>
> DEFAULT linux
> LABEL linux
> SAY Now booting USBGentoo
> KERNEL vmlinuz.img
> APPEND root=LABEL=USBGentoo initrd=initrd.img
>
> you might also add rootdelay=10 to the options if the usb stick/disk isn't
> detected quick enough
>
> umount, reboot, set the computer to boot from usb, enjoy... ;)
> Xorg without a config seems to work pretty well on most computers these
> days, IIRC the alsa modules for soundcards are also autoloaded, so you
> don't need any fancy hw detection to have a desktop running from USB
> stick ;)
>
>
> yoyo
>
>
>
> BTW there is also a "manual" way to boot even without an initrd: use
> LABEL=XXX in your fstab, on the kernel command line use root=/dev/sda2
> (or whatever you think will be more probable on you machines ;)
> then try to boot it, if it is wrong, you can enter  the corrent
> "root=/dev/sdX2" param in the syslinux prompt (you can either look up the
> correct device in the boot messages, or just try sda, sdb, sdc, ... ;)
> You could also create menu options for the usual cases... (sda...sdf
> shoud be more than enough... ;)
> You can however accidentally mount a rootfs from one of the disks on the
> computer and thus booting the system on the computer, just with your
> kernel...
>
>
>
>
Thanks for that.  I originally tried with "LABEL=UsbRoot" in both GRUB 
and fstab, but it couldn't find it, so I put it in a system that I'd 
pulled the hard drive from, so I could test if it'd work with /dev/sda 
instead.  Neither method works; it just doesn't seem to see the USB 
storage in /dev.  When I try by label, I get what's in the attached error.

I've had a quick look at SYSLINUX (and it's counterpart, EXTLINUX), and 
it appears to really be nothing more than another bootloader like LILO 
or GRUB.  Is that the case?  If so, I might try and overwrite GRUB with 
EXTLINUX and see if that works; it appears that it should be that easy.  
Most of the USB booting doco I can find seems to want SYSLINUX anyway; 
maybe I'll give it a try.  I had thought that a USB storage device is 
storage like anything else, so a "standard" install should work.  Maybe 
it doesn't...

Jake Moe