Bootless DVDs
QI have some old computers which I use to test different Linux installations, using a Lacie external DVD recorder. Now and then I buy Linux Format or some other Linux magazine with the DVDs. Recently I have met a problem with the older PCs. While starting the cover disc I see: Welcome to GRUB error:unknown filesystem. Entering rescue mode ...
grub rescue>
I wonder what the ‘grub rescue’ thinks I should do.
fossiili
AThat’s an odd one. The filesystem is a standard CD/DVD ISO9600 filesystem, nothing exotic, so you shouldn’t have any trouble booting it on anything built this century. At the point where it prints ‘Welcome to Grub’ the drive is simply reading Grub’s menu file from the DVD. We have used the same boot process on the DVD since issue 178, some two years ago (before which we used isolinux to boot the DVDs rather than Grub), so it is unlikely to be related to that, especially as you have also had the problem with different DVDs that still use isolinux.
We do test the DVDs in a range of real and virtual hardware and haven’t seen this problem before. I suspect your DVD drive may be failing if it is giving an error like this, especially as you get the error on more than one system and the drive is the common factor. A BIOS problem could be involved, but only if you have recently changed your BIOS settings as it used to work. Optical drives do age, the lasers can lose power and the lenses can get dirty, which compounds the power loss, especially if the drive is used in a dusty or smoky environment. If you have or can borrow another external drive, then you can try to eliminate the drive as the cause of the problem.
Are you booting the PC from cold? When I try to do that with an external drive on my laptop, it fails to boot from the DVD, because it has not spun up and been recognised by
the time the BIOS gives up and looks for something else to boot from. Rebooting with Ctrl-Alt-Delete, so the drive doesn’t spin down, results in a successful boot from the DVD.
The Grub rescue shell is a command line environment in which you can run Grub commands, but is only really useful if you are reasonably familiar with Grub. You cannot run standard shell commands there.