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

[Jake Moe]

On 15/09/10 20:10, YoYo Siska wrote:
> On Wed, Sep 15, 2010 at 08:34:33AM +1000, Jake Moe wrote:
>>  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:
>>>>>>>>   * 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...
> Yes, syslinux is just another "bootloader" ;) It his however
> specifically created for removable disks. I don't know how exactly grub
> works and how it handles "removable" disk (ie when the disk appears at
> different places) when finding devices for its root partition and the
> root option for kernel...
>
>> Jake Moe
>>>> Activiating mdev
>>>> Determining root device...
>> /init: line 477: blkid: not found\
> seems like your initrd is missing the blkid program (used to determine
> the labels and uuids of disks...)
> Looking at the genkernel help it seems to ethis option:
>         --disklabel             Include disk label and uuid support in your
>                                 ramdisk
>
>> !! Could not find the root block device in LABEL=UsbRoot.
>>    Please specify another value or: press Enter for hte same, type "shell" for a
>>  shell, or "q" to skip...
>> root block device(LABEL=UsbRoot) :: /dev/sda1
>>>> Mounting root...
>>>> Booting (initramfs)..
>> INIT: version 2.87 booting
>>
>> Gentoo Linux; http://www.gentoo.org/
>>  Copyright 1999-2009 Gentoo Foundation; Distributed under teh 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: Unable to resolve 'LABEL=UsbRoot'
> This means fsck was unable to find the filesystem  with that label.
> You can use dumpe2fs /dev/yourpartition to check if the filesystem
> really has the cooret label (look for "Filesystem volume name" at the
> top)
>
>>  * Filesystem couldn't be fixed :(                                        [ !! ]
>> Give root password for maintenance
>> (or type Control-D to continue):
> yoyo
>
Thanks for that, I'll rebuild the genkernel with blkid support.

As to the second suggestion, there is *no* /dev/sda1 (the partition in
question).  It just doesn't exist for some reason.  However, fstab shows
that it's mounted, and /sys/block has entries for the disk, so I'm not
sure why it's dropped out.  I'm guessing it has something to do with
udevd, or uevents?  Because shortly before that, I tell it to find the
root partition at /dev/sda1, and it starts to boot, but then it loses it.

Jake Moe