Re: Embedding a file into core.img

[Arbiel (gmx)]

Hi

You are right, Andrey, there is no need of partitionning the key. I made 
a successfull test after I posted my previous post. I have installed 
grud on the MBR of the key and made core.img look in the first, FAT32 
formatted partition for /boot/grub directory.

I wrote a simple grub.cfg file to search the partition by its name, and 
it works fine. I do not quite understand your sentence "The only thing 
I'm not sure about is line end - it may need Unix text file". I created 
my grub.cfg file with gedit, that is using Linux.

It remains a little issue at boot time. The key is /dev/sdb, the booted 
partition sits on an external device /dev/sdc. I have got a transient 
message reading "ata_id[276] HDIO_GET_IDENTITY failed for '/dev/sdc' 
illegal argument". This message does not appear when the booted 
partition sits on /dev/sda.

Le 21/03/2013 16:20, Andrey Borzenkov a écrit :
> Ð’ Thu, 21 Mar 2013 11:17:22 +0100
> "Arbiel (gmx)" <address@hidden> пишет:
>
> > Hi
> >
> > Thank you Andrey, for your help.
> >
> > I'm going to drop the idea, and return to a simplier way of doing :
> > define two partitions, the first one being Windows compatible, and a
> > little second one for the grub and GNU/Linux directories and files. I'll
> > write a regular grub.cfg file to look for the "cielos" partition.
>
> You do not really need second Linux partition, grub should be able to
> read both FAT and NTFS. The only thing I'm not sure about is line end -
> it may need Unix text file.
>
> > A question remains : will searching for an absent partition lead to a
> > "no such device" message, or, in case the search does not return any
> > value in $root, will I be able to chainload hd0, or better, to return to
> > BIOS (UEFI ?) to have it look for the next bootable device ?
>
> Grub has "exit" command. On BIOS it attempts to tell BIOS that boot
> failed, otherwise reboots. On UEFI it unfortunately always returns
> GRUB_EFI_SUCCESS which means - go to boot menu. It should return
> failure for UEFI bootmanager to try next choice. Patch is likely
> possible to extend "exit" command to accept exit code.
>
> > Arbiel
> >
> > Le 21/03/2013 06:38, Andrey Borzenkov a écrit :
> > > On Wed, Mar 20, 2013 at 11:36 PM, Arbiel (gmx)
> > > <address@hidden> wrote:
> > > > In fact, this is a first try. My goal is to look for a partition name, and
> > > > not a UUID. And when the partition has been found, I will boot immediately,
> > > > without any user action. The USB keys are to be "regular" NTFS or FAT keys,
> > > > without any track of Linux
> > >
> > > If you intended to implement it using embedded config, much more
> > > easier is to make normal grub install on USB stick and implement it in
> > > grub.cfg. Do not forget that embedded config runs very early in
> > > restricted environment (basically, in rescue mode) when very limited
> > > scripting capabilities and only subset of grub features are available.
> > > You need to enter normal mode before you can do anything useful here.
> > >
> > > > Where can I find reliable information ?
> > >
> > > Supported way to install grub is to use grub-install. grub-mkimage,
> > > embedded config, modules available etc are internal implementation
> > > details that can change from version to version and platform to
> > > platform. If you want to use them directly you probably need to follow
> > > grub development or read sources. But in your case you simply do not
> > > need it. grub-install + suitable grub.cfg is enough and makes changing
> > > configuration also easier.
> > >
> > > > Le 20/03/2013 18:40, Andrey Borzenkov a écrit :
> > > >
> > > > > Ð’ Wed, 20 Mar 2013 10:34:46 +0100
> > > > > "Arbiel (gmx)" <address@hidden> пишет:
> > > > >
> > > > > > Hi
> > > > > >
> > > > > > I try to record in the MBR of USB keys an autonomous MBR (no support of
> > > > > > any other directory or file) to boot a PC with the system located on a
> > > > > > partition whose name is predefined "cielos", and in case this fails, to
> > > > > > chainload to the hd0's MBR.
> > > > > >
> > > > > > I've understood from Grub's Manual that to achieve such a goal, I have
> > > > > > to embed the file using option -c of grub-mkimage.
> > > > > >
> > > > > > I have now modified the --grub-mkimage option to point to the shell
> > > > > > script which creates /media/maisonnette/grub/core.img and from there I
> > > > > > have been able to imbed the file and launch a boot process. However,
> > > > > > this process failed, with a "no such device : the uuid I used in my
> > > > > > search.fs_uuid command" whereas such a device exists on my external
> > > > > > device
> > > > >
> > > > > You need to include much more of grub modules than you did. At least
> > > > > you need disk driver and filesystem driver to read UUID.
> > > > >
> > > > > grub-install creates exactly the same embedded config. Why do not you
> > > > > simply use it?
> > > > >
> > > > > > The imbedded file reads
> > > > > >
> > > > > > search.fs_uuid 0aceef09-a694-4105-bade-2dca95a09a08 root
> > > > > > set prefix=(root)/boot/grub
> > > > > >
> > > > > > and a sudo blkid | grep 0aceef09-a694-4105-bade-2dca95a09a08 responds
> > > > > >
> > > > > > /dev/sdb5: LABEL="cielos" UUID="0aceef09-a694-4105-bade-2dca95a09a08"
> > > > > > TYPE="ext4"
> > > > > >
> > > > > > I try to understand why the search fails.
> > > > > >
> > > > > > Le 20/03/2013 04:18, Andrey Borzenkov a écrit :
> > > > > > > Ð’ Wed, 20 Mar 2013 00:15:07 +0100
> > > > > > > "Arbiel (gmx)" <address@hidden> пишет:
> > > > > > >
> > > > > > > > Hi
> > > > > > > >
> > > > > > > > I'm trying to embed a file into core.img. I followed instructions from
> > > > > > > > GNU Grub Manual's 5.4 Embedding a configuration file into Grub and
> > > > > > > > tried
> > > > > > > > to replicate the example given there with a config file figuring two
> > > > > > > > lines
> > > > > > > >
> > > > > > > >           search.fs_uuid the_uuid_of_my_partition root
> > > > > > > >           set prefix=($root)/boot/grub
> > > > > > > >
> > > > > > > >
> > > > > > > > I used the following commands
> > > > > > > >
> > > > > > > > #! /bin/bash
> > > > > > > > cd "${1}"
> > > > > > > > cat 1> grub/embed.cfg <<EOF
> > > > > > > > search.fs_uuid 0aceef09-a694-4105-bade-2dca95a09a08 root
> > > > > > > > set prefix=($root)/boot/grub
> > > > > > > > EOF
> > > > > > > > sudo grub-mkimage -c 'grub/embed.cfg' -o 'grub/grub-image' -O i386-pc
> > > > > > > > -d
> > > > > > > > '/usr/lib/grub/i386-pc' -C none search_fs_uuid
> > > > > > >
> > > > > > >
> > > > > > > -O and -d together are redundant.
> > > > > > >
> > > > > > > > sudo chmod +x 'grub/grub-image'
> > > > > > > > sudo grub-install --boot-directory=/media/maisonnette
> > > > > > > > --grub-mkimage=grub/grub-image /dev/sdb 2>grub/msg.log
> > > > > > >
> > > > > > > --grub-mkimage points to program to create image, not to image itself.
> > > > > > >
> > > > > > > You do not explain what you attempt to achieve. May be using grub-rescue
> > > > > > > to build ISO image that includes full grub and can optionally include
> > > > > > > arbitrary files would be easier?
> > > > > > >
> > > > > > > > I get the following error message
> > > > > > > >
> > > > > > > > grub/grub-image: 1: grub/grub-image: Syntax error: word unexpected
> > > > > > > > (expecting ")")
> > > > > > > >
> > > > > > > > Can anybody tell me what's wrong, knowing that my partition
> > > > > > > > /media/maisonnette has nothing to do with the
> > > > > > > > 0aceef09-a694-4105-bade-2dca95a09a08 partition.
> > > > > > > >
> > > > > > > > Thank you
> > > > > > > >
> > > > > > > > I used the following command
> > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > > >
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