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

[Walter Dnes]

On Sun, Jun 13, 2021 at 05:38:53PM -0000, Grant Edwards wrote
> On 2021-06-13, Walter Dnes <waltdnes@××××××××.org> wrote:
>
> >   I'd be tempted to do a manual gub.cfg if I had documentation.
>
> I gave up on the grub2 auto-magical config system many years ago. My
> grub.cfg is typically 10-20 lines long. The documentation is at
>
>   https://www.gnu.org/software/grub/manual/grub/grub.html
>
> For manual confiuration: see section 6:
>
>   https://www.gnu.org/software/grub/manual/grub/html_node/Configuration.html#Configuration

  When experimenting with this, I'll backup grub.cfg.  If things go
awry, boot with the USB key I used for the install, and copy back the
old known working grub.cfg.  I've done a first crack at this.  I assume
that nothing in /etc/default/grub will have any effect.  Questions...

1) Is "insmod extfs3" necessary? I've built extfs3 into the kernels.
2) I assume that the the first "menuentry" will be the default boot?
3) Is the default timeout still 5 seconds?
3) I assume that 640x480 is supported on just about every monitor
out there.  I want as large text as possible.  My eyes are getting
old... just like me.  Any obvious errors in the following grub.cfg?

=====================================================================
menuentry 'Linux Experimental' --class gnu-linux {
        set gfxpayload=640x480
        insmod ext3fs
        set root='hd0,gpt1'
        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 {
        set gfxpayload=640x480
        insmod ext3fs
        set root='hd0,gpt1'
        linux   /vmlinuz-experimental root=/dev/sda2 ro
}
menuentry 'Linux Production' --class gnu-linux { 
        set gfxpayload=640x480
        insmod ext3fs
        set root='hd0,gpt1'
        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 { 
        set gfxpayload=640x480
        insmod ext3fs
        set root='hd0,gpt1'
        linux   /vmlinuz-production root=/dev/sda2 ro
}
=====================================================================

  Something that occured to me.  Can I move the duplicated lines to the
top of the file and take them out of the menuentries?  E.g.

=====================================================================
        set gfxpayload=640x480
        insmod ext3fs
        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@××××××××.org>
I don't run "desktop environments"; I run useful applications