Comments on Matt's blog: Booting to ISO images from a USB key

OK, sorry, I should have looked further on the &qu...

2010-10-15T03:55:00.080-04:00

OK, sorry, I should have looked further on the "BIOS" error, using "--recheck" seems to help that, however now I get a grub shell and no menu. I have two iso's in the folder, and a sensible looking grub.cfg

I just tried this and got a message: "/dev/sd...

2010-10-14T10:54:22.554-04:00

I just tried this and got a message: "/dev/sdb does not have any corresponding BIOS drive." after the grub-install stage.

Any ideas what the problem may be? I now have a boot/grub folder with a single file, device.map, with a single line, "(fd0) /dev/fd0" - nothing else.

Well, vfat is conveniently just how filesystems ar...

2010-10-14T09:14:11.192-04:00

Well, vfat is conveniently just how filesystems are set up on brand new USB keys, so jordanu's comment about having a system to run the script on applies there -- what I mean by this is you *could* add the ISOs under windows, but then if you don't also have python you can't run the script to update the grub menu. Furthermore, it means you don't really need to format the key if it's a new one.

In reality, vfat or another filesystem won't really make much of a difference for this.

My feeling was that since you have to add the isos in the first place, running the script is just an extra step that can be done quickly.

With all this in mind, I'll prepare a few USB keys with this trick to help other installing at tonight's release party in Montreal. We'll see what kind of feedback will come out ;)

Why do you use vfat for the filesystem instead of ...

2010-10-13T22:37:17.401-04:00

Why do you use vfat for the filesystem instead of ext4 (with journaling turned off) or another, more efficient filesystem?

"cute, but I feel autoiso.cfg is doing quite ...

2010-10-13T19:42:49.349-04:00

"cute, but I feel autoiso.cfg is doing quite a lot of checking and multiple passes over an ISO, which doesn't happen with my script."

It's true that your script lists the files in the iso once, then checks that cached list, whereas autoiso.cfg currently does one "pass" checking for each type of iso supported (exiting when it finds one, so only one pass if the iso has a loobpack.cfg). But I hope that grub's metadata caching means that in effect the same thing is happening in autoiso.cfg. I.e. The directory is read once into RAM then consulted multiple times when checking for files. I'll have to do some actual performance tests to see where it could be made faster.

Also of course your script is run once, then the static grub.cfg is used multiple times, whereas autoiso.cfg does the detection at every boot. For me the advantage of not requiring a system which can run update-grub.py to add new isos outweighs the disadvantage of the menu taking slightly longer to load each boot.

"OTOH, if loopback.cfg means I can have "submenus" or in a way delegate to the iso giving out choices (a la "live or graphical installer?", read maybe-ubiquity), that's pretty interesting."

That's exactly what it means :)

jordanu: cute, but I feel autoiso.cfg is doing qui...

2010-10-13T09:32:12.276-04:00

jordanu: cute, but I feel autoiso.cfg is doing quite a lot of checking and multiple passes over an ISO, which doesn't happen with my script. OTOH, if loopback.cfg means I can have "submenus" or in a way delegate to the iso giving out choices (a la "live or graphical installer?", read maybe-ubiquity), that's pretty interesting.

samtygier: thanks for the catches, I'll fix the script in bzr and my post :)

not sure if my previous comment got though. when p...

2010-10-13T07:08:35.068-04:00

not sure if my previous comment got though. when pasting the grub command make sure you get a double hyphen instead of an emdash. otherwise you get an error like "More than one install_devices?".

also i think it should be
sudo grub-install --root-directory=/media/DISKNAME/ /dev/sdc

with sudo, the full mountpoint, and the disk rather than the partition.

also the shebang line in the script is wrong. it is missing the '!', and should probably be
#!/usr/bin/env python

otherwise it works for me. nice to have the i386 and amd64 on the same usb stick.

For isos containing a /boot/grub/loopback.cfg, lik...

2010-10-13T04:50:26.364-04:00

For isos containing a /boot/grub/loopback.cfg, like the Ubuntu 10.10 isos, please use that rather than hard coding the kernel paths / parameters. More info here http://www.supergrubdisk.org/wiki/Loopback.cfg

Also grub 1.99 will hopefully ship, as part of the official documentation, an example grub.cfg that will actually detect iso files at boot. So you can just add iso files to the flash drive without needing to modify the grub.cfg at all. If you want to see the beginnings of this autoiso.cfg you can find it here: http://lists.gnu.org/archive/html/grub-devel/2010-09/msg00080.html

"+junk" ! That's hilarious-ly humble...

2010-10-13T00:31:18.884-04:00

"+junk" ! That's hilarious-ly humble :D

BTW many thanks for all the help and ideas you bring to the support team :D Always HAPPY to have you around!!!