bootstrapping from a USB stick

[Tod Merley]

Flash drives tend to have firmware ahead of the "drive" access and
sometimes that means that they simply will not work as a boot device.

I am having good luck with Kingston DataTraveler G4 series drives.  What I
do to load a Linux (Ubuntu 12 and Fedora 20 tried so far) is to first work
with Gparted.  The drive has some unallocated space before the main data
partition - which I make sure I do not touch.  What I do is simply -
starting from the end of the data portion - shorten that portion to make
space for the Linux.  Then I install the Linux using the normal live DVD
installer to the flash drive into the large unallocated space I just
created - having it make an MBR on the device.

If the bios on your oldish computer will allow booting from flash drives I
think it is not a bad approach.

I have made Clonezilla images of some of my thus formed flash drives which
do work well.  But I have not tried using those images to make a new drive
from the saved image.  The thing is that the process of making an updated
LInux on a drive takes a long time.  If this works it will save a lot of
time (for my projects with these drives) and in your situation it would be
good to keep a working spare as flash drives, at least for me, tend to
simply stop working after a year or two.

Please do let us know how it works out.


On Sun, Aug 31, 2014 at 12:40 PM, Chris Murphy <lists at colorremedies.com>
wrote:

>
> On Aug 31, 2014, at 9:00 AM, D. Hugh Redelmeier <hugh at mimosa.com> wrote:
>
> > I have an oldish PC that only understands booting from 512-byte
> > sectors and then only with MBR disks.
> >
> > I want to install large new disks on it, and no old disks.  These
> > don't even pretend to do 512-byte sectors: 4k all the way (3T and 4T
> sizes
> > aren't good for MBR either).
>
> Uhhh, I haven't seen bare drives in the wild with 4096 byte logical and
> physical sectors. What's the model of this drive? I've only seen some USB
> enclosures that do this, and present a 4096 byte logical sector: and only
> then they come with a drive already in them, they're not empty enclosures.
> The problem some people have is if the enclosure craps out they try to
> recover their data and they're SOL because the enclosure caused the drive
> to present 4096 logical sectors, but the drive itself presents 512 byte
> logical sectors, and the mismatch makes the drive unreadable, unmountable,
> because all the reported LBAs are totally wrong. So you have to get a
> replacement enclosure… well at least, that's the easiest way to deal with
> it. Maybe someone could hack up a way to do the same thing as the enclosure
> in software with device mapper (?), that'd be useful.
>
> Old PC's might be OK with GPT so long as there's also a protective MBR. By
> default anaconda/blivet (the Fedora installer), creates a protective MBR,
> but also sets a non-standard flag its 0xEE entry that tricks most computer
> BIOS into accepting GPT. But there are quite a few BIOS that will just face
> plant. So you have to test it to know for sure.
>
>
> > I was thinking that I should be able to use a USB flash memory stick
> > as the boot device, loading GRUB from there, and then having it boot
> > the OS from a big GPT hard disk.  The stick would be permanently
> > plugged in.
> >
> > Is there any reason that this might not work?  Is there a better way?
>
> You could try the above. If not then fall back to your idea. At install
> time, choose both flash drive and hard drive as installation destinations.
> Put the /boot mount point on the flash drive, and everything else on the
> hard drive.
>
>
> >
> > Are there special GRUB modules that I need to convince GRUB's
> > installer to put on the USB stick?
>
> No. grub2-install will figure this out, anaconda has already mounted the
> system as it will be used, and has written an fstab that describes how it's
> to be mounted, and grub2-install reads that and figures out that the flash
> drive with /boot on it should receive grub's core.img embedded in the MBR
> gap. Once that core.img is read, the BIOS is out of the picture.
>
> > What filesystem type is best for the USB stick?  My guess: ext4 is
> > fine.
>
> Doesn't really matter it's mainly read-only. It'll only be written to when
> doing kernel updates.
>
>
> Chris Murphy
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