[lfs-support] Boot Issues

Casey Daniels lfs at cd.kcfam.net
Fri Sep 27 20:04:29 PDT 2013

> http://www.linuxquestions.org/questions/linux-from-scratch-13/booting-lfs-from-usb-stick-897465/
> might have something useful in it (for the grub suggestions).  There
> have been many threads here over the years, but the mail archives
> aren't available so I can no longer point you to them.
> ĸen
Update on the problem, and going to explain what I did so if others run 
into the problem, they will hopefully be able to use it.

the message I kept getting goes as follows

VFS: Can't open root device "sda1" or unknown-block(0,0): error -6

Apparently there the key to the problem is the (?,?) part of the 
message.  From what I learned searching there are two possible causes of 
getting this message, the device isn't there, or VFS can't do with 
anything with the Partition that is there.

(0,0) tells you that there is no device there or at least VFS can't see it.

(X,Y) with at least X or Y not being 0 tells you that its a file system 

Try as I might i couldn't figure out what was wrong with the Device, 
until doing other searching, apparently USB Drives, RAIDS, Network 
Boots, and even some slow internal Hard Drives aren't available for VFS 
instantly, but the VFS is very impatient and panic if it doesn't have it 
right away.

Solution to all of this?  Tell VFS to take a nap while the Kernel does 
its job to connect everything else.

So in the grub.cfg file line

linux   /boot/vmlinuz-3.10.12-lfs-7.4 root=/dev/sda1 ro

add rootdelay=???  with ??? being the number of seconds you wait VFS to 
wait before mounting the root file system.

so it will read something like

linux   /boot/vmlinuz-3.10.10-lfs-7.4 root=/dev/sda2 rootdelay=120 ro

Caution here from what I read about the rootdelay sounds like the VFS 
will keep trying to mount root for the whole time before panicking (if 
it does come up before the time period it boot sooner). but from what I 
noticed is VFS actually just doesn't do anything for the whole time 
period so some trial and error be necessary to bring the number down to 
a reasonable wait but still give everything enough time for the Kernel 
to do its thing.  There is another option rootwait, but from what I can 
tell it will cause the the VFS to go Rip Van Winkle on you and never 
error out if the file system fails to become available.

Hopefully my 3-4 days chasing this around will help someone in the 
future, thank you for your guy's help

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