Tom at 13:46, 31 December 2017

2017-12-31T13:46:30Z

Tom at 13:45, 31 December 2017

2017-12-31T13:45:32Z

Tom: Created page with "Putting a rescue image on the harddisk in case normal boot doesn't work anymore. =Where to put files and configure grub= Files can be put in /boot, but in that case it's not..."

2017-12-31T13:44:31Z

Created page with "Putting a rescue image on the harddisk in case normal boot doesn't work anymore. =Where to put files and configure grub= Files can be put in /boot, but in that case it's not..."

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Putting a rescue image on the harddisk in case normal boot doesn't work anymore.

=Where to put files and configure grub=
Files can be put in /boot, but in that case it's not possible from within the rescue boot to do anything with the boot partition as it will have the iso image mounted. To avoid this, an additional partition was created and mounted as /mnt/rescue (location doesn't matter).
In theory, only the iso image is needed. Copy install-amd64-minimal-20170907.iso to /mnt/rescue.

As it's running on Qemu there's an additional problem that the virtio modules are not present in the initrd. To add these, the initrd has to be unpacked, the virtio modules added and repacked. First mount the iso image:
<source lang="sh">
mount -o loop /mnt/rescue/install-amd64-minimal-20170907.iso /mnt/tmp
</source>

Extract the initrd:
<source lang="sh">
mkdir /tmp/initrd
cd /tmp/initrd
xzcat /mnt/tmp/isolinux/gentoo.igz | cpio -ivmud
</source>

Mount the squashfs image and copy the modules, to add disk support at least virtio_blk.ko and virtio_pci.ko have to be added:
<source lang="sh">
mount -o loop /mnt/tmp/image.squashfs /mnt/tmp2
cp /mnt/tmp2/lib/modules/4.12.5-gentoo/kernel/drivers/block/virtio_blk.ko /tmp/initrd/lib/modules/4.12.5-gentoo/kernel/drivers/block/
cp /mnt/tmp2/lib/modules/4.12.5-gentoo/kernel/drivers/virtio/virtio* /tmp/initrd/lib/modules/4.12.5-gentoo/kernel/drivers/virtio/
</source>

Repack the initrd:
<source lang="sh">
find . -print | cpio -o -H newc | xz -9 -C none > /mnt/rescue/gentoo-minimal-20170907.igz
</source>

Create the grub entry (in /etc/grub.d/40_custom):
<source>
menuentry "Gentoo minimal 20170907" {
insmod gzio
insmod part_gpt
insmod ext2
search --no-floppy --fs-uuid --set=boot cddcff7f-81ef-45e9-9329-66056308b7bb
search --no-floppy --fs-uuid --set=rescue 80eb8826-6e3e-4b7a-aa82-bfc59e4e9eb7
loopback loop ($rescue)/"install-amd64-minimal-20170907.iso"
linux (loop)/isolinux/gentoo root=/dev/ram0 init=/linuxrc dokeymap looptype=squashfs loop=/image.squashfs cdroot initrd=($boot)/gentoo-minimal-20170907.igz doload=virtio_pci,virtio_blk vga=791 isoboot=/install-amd64-minimal-20170907.iso
# initrd (loop)/isolinux/gentoo.igz
initrd ($rescue)/gentoo-minimal-20170907.igz
}

menuentry "Gentoo minimal 20170907 nofb" {
insmod gzio
insmod part_gpt
insmod ext2
search --no-floppy --fs-uuid --set=boot cddcff7f-81ef-45e9-9329-66056308b7bb
search --no-floppy --fs-uuid --set=rescue 80eb8826-6e3e-4b7a-aa82-bfc59e4e9eb7
loopback loop ($rescue)/"install-amd64-minimal-20170907.iso"
linux (loop)/isolinux/gentoo root=/dev/ram0 init=/linuxrc dokeymap looptype=squashfs loop=/image.squashfs cdroot initrd=($boot)/gentoo-minimal-20170907.igz doload=virtio_pci,virtio_blk isoboot=/install-amd64-minimal-20170907.iso
# initrd (loop)/isolinux/gentoo.igz
initrd ($rescue)/gentoo-minimal-20170907.igz
}
</source>

In the above block, the UUIDs are for the boot and rescue partition respectively.
Also required is the option '''doload=virtio_pci,virtio_blk''' which will tell the initrd to actually load these modules.
The option '''isoboot=/install-amd64-minimal-20170907.iso''' is also required to tell the initrd that it should first look for the iso file, before looking for the image.squashfs which is inside the iso file.
The commented initrd line could be used if the initrd image already contained the virtio drivers (maybe in the future).

← Older revision		Revision as of 13:46, 31 December 2017
Line 61:		Line 61:
	The option '''isoboot=/install-amd64-minimal-20170907.iso''' is also required to tell the initrd that it should first look for the iso file, before looking for the image.squashfs which is inside the iso file.		The option '''isoboot=/install-amd64-minimal-20170907.iso''' is also required to tell the initrd that it should first look for the iso file, before looking for the image.squashfs which is inside the iso file.
	The commented initrd line could be used if the initrd image already contained the virtio drivers (maybe in the future).		The commented initrd line could be used if the initrd image already contained the virtio drivers (maybe in the future).
		+
		+	To actually activate the new grub settings:
		+	<source lang="sh">
		+	grub-mkconfig -o /boot/grub/grub.cfg
		+	</source>

@@ Line 28: / Line 28: @@
 find . -print | cpio -o -H newc | xz -9 -C none > /mnt/rescue/gentoo-minimal-20170907.igz
 </source>
 Create the grub entry (in /etc/grub.d/40_custom):

Gentoo minimal boot rescue on Qemu - Revision history

Tom at 13:46, 31 December 2017

Tom at 13:45, 31 December 2017

Tom: Created page with "Putting a rescue image on the harddisk in case normal boot doesn't work anymore. =Where to put files and configure grub= Files can be put in /boot, but in that case it's not..."