Re: [gentoo-user] Re: Exact setting in grub to default to a kernel by name?

["Walter Dnes" <waltdnes@waltdnes.org>]

On Mon, Jun 14, 2021 at 12:20:44AM +0100, Neil Bothwick wrote
> On Sun, 13 Jun 2021 18:57:49 -0400, Walter Dnes wrote:
> 
> /etc/default/grub is only used when you call grub-mkconfig.
> 
> > 1) Is "insmod extfs3" necessary? I've built extfs3 into the kernels.
> 
> If the kernel is on an ext3 filesystem, yes. This is GRUB's module, it
> uses it to read an ext3 filesystem in order to load the kernel.

  Some confusion here.  "fdisk -l" on my new machine gives...

Device          Start        End    Sectors   Size Type
/dev/sda1        2048     526335     524288   256M EFI System
/dev/sda2      526336 1886416303 1885889968 899.3G Linux filesystem
/dev/sda3  1886418352 1953523119   67104768    32G Linux filesystem

  The EFI Systen partition is fat32.  The web examples I read show
"insmod <filesystem>" matching the filesystem of the linux system being
booted.  But all entries in grub.cfg on my new machine are "insmod fat".
I wonder if the web documentation was referring to BIOS-booting machines.
grub.cfg would be sitting on an xfs or extfs3 or whatever file system,
and would need to read it off that filesystem.

  I have a UEFI system which demands a fat32 boot partition.  Since grub
and the kernels are sitting on a fat32 partition, my machine needs
"insmod fat".

  Things that make you go hmmmm...
* you need to put "insmod fat" in grub.cfg to tell grub that the kernels
  are sitting on a fat32 partition
* but grub has to first read grub.cfg on the fat32 partition before it
  knows that it must read a fat32 partition

  I wonder if this is due to the verbose automagic configuration.  I
also noticed that all menuentries on my machine contain "insmod gzio
and "insmod part_gpt", so I'm including them here.  Here is my proposed
grub.cfg.  If anybody sees any problems, please let me know.  Otherwise,
I'll try the following tomorrow on the new machine...

========================================================================

        set timeout_style=menu
        set timeout=15
        insmod vga
        set gfxpayload=640x480
        insmod gzio
        insmod part_gpt
        insmod fat
        set root='hd0,gpt1'
menuentry 'Linux Experimental' --class gnu-linux {
        linux   /vmlinuz-experimental root=/dev/sda2 ro  noexec=on net.ifnames=0 intel_pstate=disable ipv6.disable=1
}
menuentry 'Linux Experimental Recovery' --class gnu-linux {
        linux   /vmlinuz-experimental root=/dev/sda2 ro
}
menuentry 'Linux Production' --class gnu-linux {
        linux   /vmlinuz-production root=/dev/sda2 ro  noexec=on net.ifnames=0 intel_pstate=disable ipv6.disable=1
}
menuentry 'Linux Production Recovery' --class gnu-linux {
        linux   /vmlinuz-production root=/dev/sda2 ro
}


-- 
Walter Dnes <waltdnes@waltdnes.org>
I don't run "desktop environments"; I run useful applications