[Date Prev][Date Next] [Thread Prev][Thread Next] [Date Index] [Thread Index]

Re: Grub-less installation of stretch

Le 08/10/2018 à 18:37, David Wright a écrit :

(The origin of my system will differ slightly in being debootstrap
from another partition running jessie, rather than an upgrade of
an older system.)

At step 3 (where I'm installing all the packages I want on the new
system) remove grub if it's there. (IOW I wouldn't deliberately be
installing it. I see no dependencies.)

Step 4 as above.

Step 5: Now I'm back running jessie (whence I executed the
debootstrap and so on).

# grub-mkconfig > /boot/grub/grub.cfg

which will os-prober the new grub-less system and add entries for it under
### BEGIN /etc/grub.d/30_os-prober ###

Step 6:

# grub-set-default 'Debian 9 (on /dev/sda7)>osprober-gnulinux-simple-swan07'

using the strings I find there.

# reboot

Would this work, and reboot into the grub-less system? Any snags or gotchas?

Maybe, maybe not. The problem with a GRUB-less installation is the lack of /boot/grub/grub.cfg. Without it (or /etc/lilo.conf or /boot/grub/menu.lst), grub-mkconfig/os-prober cannot guess the correct parameters for the kernel command line. This includes not only parameters defined by the GRUB_CMDLINE_LINUX* variables in /etc/default/grub but also the root= parameter. Unfortunately, without a hint from an existing boot loader config file, it appears that grub-mkconfig will use the raw and possibly non-persistent root device name, e.g. /dev/sda7 instead of the UUID, or /dev/dm-2 instead of the LVM logical volume or encrypted device name.

It may work if the root device is a plain partition whose name does not change (e.g. because there is only one disk) and the system does not require custom kernel parameters. Remember that logical partition numbers may change when creating or deleting another logical partition.

But it won't work if the system requires custom kernel parameters or the root device is an LVM logical volume or encrypted device, because the initramfs needs root= to specify the proper form /dev/mapper/* in order to activate and find the device.

So it may be advisable to install at least grub-common and use grub-mkconfig to generate /boot/grub/grub.cfg. If you also want to automatically update grub.cfg after a kernel package installation or removal, you may either install grub-pc (or any other grub flavour available in the arch) - without installing the boot loader - or create your own scripts in /etc/kernel/post{inst,rm}.d/ to do basically the same as zz-update-grub provided by grub-pc.

Reply to: