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Re: Full documentation for GRUB2

From: Robert Wolf
Subject: Re: Full documentation for GRUB2
Date: Fri, 1 Apr 2011 12:42:40 +0200 (CEST)
User-agent: Alpine 2.02 (DEB 1266 2009-07-14)


the reason for my request of the complete grub2 documentation did come when I 
wanted to boot ubuntu livecd and knoppix livedvd from NTFS partition of windows 

It is possible to boot these livecd/dvd distros from HD without installing and 
without booting it from CD/DVD medium. But you need some better boot loader as 
Windows boot loader. I did some tests with USB flash drive using syslinux and 
it works. But USB flash is not so fast and "stable" as normal HD.

So I have copied ubuntu ISO and Knoppix files to HD with NTFS. AFAIK grub 
legacy does not support NTFS, so I decided to grub2.

I have started ubuntu live CD from CD and I wanted to install grub2 as written 
in the manual using "grub-install /dev/sda"

But there is a problem. The running liveCD system has no real partition with 
/boot and the grub-install writes error:

# grub-install /dev/sda
/usr/sbin/grub-probe: error: cannot find a device for /boot/grub (is /dev 

Ok, I found the solution using --root-directory

# mkdir /root/d
# mount /dev/sda2 /root/d
# grub-install --root-directory=/root/d /dev/sda
Installation finished. No error reported.

Fine, grub2 is installed, now the config. I have read the config is generated 
using update-grub. I wanted to generate basic template and then update it for 
my needs. But 

# update-grub
/usr/sbin/grub-probe: error: cannot find a device for / (is /dev mounted?).

Other problem - grub-probe cannot handle aufs (unionfs). In fact, update-grub 
is only wrapper to grub-mkconfig, but grub-mkconfig has no option to skip 
grub-probe. So I have ended without config.

But this should be no problem, I can write menu.lst for grub legacy, it should 
no be so much complex to write grub.cfg for grub2. I wanted hidden menu with 
timeout 5 seconds and show menu if ESC pressed. If none press the key, it will 
boot Windows Vista, if anyone (me) press the key, he can choose ubuntu or 
knoppix live.

For the hidden menu, I have found the functionality in /etc/grub.d and 
/etc/defaults/grub and then I wanted to see possibilities and I have found, 
that some commands are missing in the official documentation. I found the 
description on some other page.

The source-code reading is "solution" only for those, who really have free time 
and who understand source code. If I could vote, it would be better, if the 
developers write documentation too - does not matter if only short comment in 
source code or in the command help (--help) or detailed description in the 
documentation file. At least short comment with parameters description and 
possible values would be very nice, because other people can better understand 
the code and make tests and write more detailed documentation.



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