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Re: Grub-less installation of stretch

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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.

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Thread

Grub-less installation of stretch David Wright <deblis@lionunicorn.co.uk> - 2018-10-08 18:40 +0200
  Re: Grub-less installation of stretch Pascal Hambourg <pascal@plouf.fr.eu.org> - 2018-10-08 20:30 +0200
    Re: Grub-less installation of stretch David Wright <deblis@lionunicorn.co.uk> - 2018-10-08 22:30 +0200
      Re: Grub-less installation of stretch Pascal Hambourg <pascal@plouf.fr.eu.org> - 2018-10-08 23:50 +0200
        Re: Grub-less installation of stretch David Wright <deblis@lionunicorn.co.uk> - 2018-10-09 22:10 +0200

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