[gentoo-user] Grub2, chroot, initramfs

[gentoo-user] Grub2, chroot, initramfs

[Paul Hartman]

Hi,

I'm trying out grub2 for the first time on my old laptop. I'm
following the guide at: https://wiki.gentoo.org/wiki/GRUB2_Quick_Start
which seems easy enough. Basically just emerge it, install and go.

However... two different questions:

When I did this from a chroot, I just got the GRUB> prompt upon
rebooting... no menu or anything. I can manually type "linux
/boot/vmlinuz root=/dev/sda3" and then boot into my system. When I run
grub2-mkconfig from within the chroot, I don't get any "Found linux
image" lines. It does not create /boot/grub2/grub.cfg but rather
grub.cfg.new. So I don't know if it's confused about where /boot is or
what. Is there a trick to installing/updating grub2 config from within
a chroot?

Second, when running grub2-mkconfig from within my working gentoo
system, it fails with "error: failed to get canonical path of
/dev/root." which is apparently because I don't use an initramfs. I
must manually run "ln -s /dev/sda3 /dev/boot" before it will work. Is
there any trick to avoid having to do that every time? For now I have
simply added that to my after-kernel-update script but I'm curious to
know if grub2 knows how to handle this on its own somehow.

Thanks,
Paul

Re: [gentoo-user] Grub2, chroot, initramfs

[Hilco Wijbenga]

On 15 May 2012 19:37, Paul Hartman <paul.hartman+gentoo@gmail.com> wrote:
> Hi,
>
> I'm trying out grub2 for the first time on my old laptop. I'm
> following the guide at: https://wiki.gentoo.org/wiki/GRUB2_Quick_Start
> which seems easy enough. Basically just emerge it, install and go.
>
> However... two different questions:
>
> When I did this from a chroot, I just got the GRUB> prompt upon
> rebooting... no menu or anything. I can manually type "linux
> /boot/vmlinuz root=/dev/sda3" and then boot into my system. When I run
> grub2-mkconfig from within the chroot, I don't get any "Found linux
> image" lines. It does not create /boot/grub2/grub.cfg but rather
> grub.cfg.new. So I don't know if it's confused about where /boot is or
> what. Is there a trick to installing/updating grub2 config from within
> a chroot?

I don't really understand where the chroot comes into this but ... did
you add the "-o /boot/grub2/grub.cfg" part? I forgot that bit a few
times and then couldn't figure out why my changes weren't taking
effect. :-)

> Second, when running grub2-mkconfig from within my working gentoo
> system, it fails with "error: failed to get canonical path of
> /dev/root." which is apparently because I don't use an initramfs. I
> must manually run "ln -s /dev/sda3 /dev/boot" before it will work. Is
> there any trick to avoid having to do that every time? For now I have
> simply added that to my after-kernel-update script but I'm curious to
> know if grub2 knows how to handle this on its own somehow.
>
> Thanks,
> Paul
>

Re: [gentoo-user] Grub2, chroot, initramfs

[Paul Hartman]

On Tue, May 15, 2012 at 9:53 PM, Hilco Wijbenga
<hilco.wijbenga@gmail.com> wrote:
> On 15 May 2012 19:37, Paul Hartman <paul.hartman+gentoo@gmail.com> wrote:
>> Hi,
>>
>> I'm trying out grub2 for the first time on my old laptop. I'm
>> following the guide at: https://wiki.gentoo.org/wiki/GRUB2_Quick_Start
>> which seems easy enough. Basically just emerge it, install and go.
>>
>> However... two different questions:
>>
>> When I did this from a chroot, I just got the GRUB> prompt upon
>> rebooting... no menu or anything. I can manually type "linux
>> /boot/vmlinuz root=/dev/sda3" and then boot into my system. When I run
>> grub2-mkconfig from within the chroot, I don't get any "Found linux
>> image" lines. It does not create /boot/grub2/grub.cfg but rather
>> grub.cfg.new. So I don't know if it's confused about where /boot is or
>> what. Is there a trick to installing/updating grub2 config from within
>> a chroot?
>
> I don't really understand where the chroot comes into this but ... did
> you add the "-o /boot/grub2/grub.cfg" part? I forgot that bit a few
> times and then couldn't figure out why my changes weren't taking
> effect. :-)

Hehe, yeah, I used that command. I'm installing it from chroot for the
first time because gentoo's bootloader was not yet present on the
machine (only Windows7).

Re: [gentoo-user] Grub2, chroot, initramfs

[Hinnerk van Bruinehsen]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On 16.05.2012 04:37, Paul Hartman wrote:
> Hi,
> 
> I'm trying out grub2 for the first time on my old laptop. I'm 
> following the guide at:
> https://wiki.gentoo.org/wiki/GRUB2_Quick_Start which seems easy
> enough. Basically just emerge it, install and go.
> 
> However... two different questions:
> 
> When I did this from a chroot, I just got the GRUB> prompt upon 
> rebooting... no menu or anything. I can manually type "linux 
> /boot/vmlinuz root=/dev/sda3" and then boot into my system. When I
> run grub2-mkconfig from within the chroot, I don't get any "Found
> linux image" lines. It does not create /boot/grub2/grub.cfg but
> rather grub.cfg.new. So I don't know if it's confused about where
> /boot is or what. Is there a trick to installing/updating grub2
> config from within a chroot?
> 
> Second, when running grub2-mkconfig from within my working gentoo 
> system, it fails with "error: failed to get canonical path of 
> /dev/root." which is apparently because I don't use an initramfs.
> I must manually run "ln -s /dev/sda3 /dev/boot" before it will
> work. Is there any trick to avoid having to do that every time? For
> now I have simply added that to my after-kernel-update script but
> I'm curious to know if grub2 knows how to handle this on its own
> somehow.
> 
> Thanks, Paul
> 

If I recall correctly you need to mount /sys for grub2 to sucessfully
detect devices.
mount -o bind /sys <path-to-gentoo/sys should suffice.
proc and dev should be mounted according to the manual.

If you use a /boot- partition mount it, when you are inside the chroot.
Doing so it worked like a charm for all devices I installed that way
(3 in the last 3 months, if I recall correctly).

With kind regards,

Hinnerk

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