7:40 p.m.
Can anyone try using grubby --set-default to change the default boot kernel
to something other than the most recently-installed kernel, successfully?
It tells me that it obeys my request, and grubby --info=DEFAULT shows that
the default boot kernel is what I specified.
But at boot the grub menu still highlights the most recently installed
kernel, and that's what boots by default.
8:03 p.m.
On Sat, 07 Jan 2023 20:40:18 -0500
Sam Varshavchik wrote:
But at boot the grub menu still highlights the most recently
installed
kernel, and that's what boots by default.
If you can stand looking through the scripts that are used to build
the grub.cfg (I think they may live in /etc/grub.d) you will find
massively unintelligible scripts implementing impossible to decode
logic to decide all kinds of things, including the default kernel.
It is possible the actual default is determined by grub environment
file setting.
I gave up trying to figure out how to get the scripts to do what
I wanted in an official fashion and just have a script that runs after
dnf to fix any stuff I don't want in the grub.cfg file.
https://tomhorsley.com/game/Mjolnir.html
10:14 p.m.
Tom Horsley writes:
On Sat, 07 Jan 2023 20:40:18 -0500
Sam Varshavchik wrote:
> But at boot the grub menu still highlights the most recently installed
> kernel, and that's what boots by default.
If you can stand looking through the scripts that are used to build
the grub.cfg (I think they may live in /etc/grub.d) you will find
massively unintelligible scripts implementing impossible to decode
logic to decide all kinds of things, including the default kernel.
--set-default does not update grub.cfg. The default kernel setting is …
somewhere.
I distinctly recall there was an entry in /etc/default/grub that specified
it. It's not there any more.
It is possible the actual default is determined by grub environment
file setting.
Well, yes. After some random poking:
grub2-editenv list
This shows the default kernel boot that grubby sets.
Except that it has absolutely no effect whatsoever. I see that grubby
updates this. But grub, when it boots, completely ignores the default entry
that's shown here.
I gave up trying to figure out how to get the scripts to do what
I wanted in an official fashion and just have a script that runs after
dnf to fix any stuff I don't want in the grub.cfg file.
This has all the telltale signs of grub's default boot kernel setting name's
getting renamed or changed, but grubby was not updated, accordingly, so it
thinks it's setting the default boot kernel, but grub doesn't read it. The
environment file, /boot/grub2/grubenv, is just a generic name=value store,
that you can toss any random names and values in there, from the looks of it.
While I was typing this out I remembered that the actual bootloader gets
installed by grub-install. Perhaps grub and grubby were updated, but grub-
install did not ran.
And after a "/sbin/grub-install /dev/sda", the default boot kernel setting,
made by grubby, started working. Another Scooby-Doo mystery solved…
1:36 a.m.
On 8/1/23 15:14, Sam Varshavchik wrote:
Tom Horsley writes:
> On Sat, 07 Jan 2023 20:40:18 -0500
> Sam Varshavchik wrote:
>
> > But at boot the grub menu still highlights the most recently installed
> > kernel, and that's what boots by default.
>
> If you can stand looking through the scripts that are used to build
> the grub.cfg (I think they may live in /etc/grub.d) you will find
> massively unintelligible scripts implementing impossible to decode
> logic to decide all kinds of things, including the default kernel.
--set-default does not update grub.cfg. The default kernel setting is
…somewhere.
I distinctly recall there was an entry in /etc/default/grub that
specified it. It's not there any more.
> It is possible the actual default is determined by grub environment
> file setting.
Well, yes. After some random poking:
grub2-editenv list
This shows the default kernel boot that grubby sets.
Except that it has absolutely no effect whatsoever. I see that grubby
updates this. But grub, when it boots, completely ignores the default
entry that's shown here.
> I gave up trying to figure out how to get the scripts to do what
> I wanted in an official fashion and just have a script that runs after
> dnf to fix any stuff I don't want in the grub.cfg file.
This has all the telltale signs of grub's default boot kernel setting
name's getting renamed or changed, but grubby was not updated,
accordingly, so it thinks it's setting the default boot kernel, but
grub doesn't read it. The environment file, /boot/grub2/grubenv, is
just a generic name=value store, that you can toss any random names
and values in there, from the looks of it.
While I was typing this out I remembered that the actual bootloader
gets installed by grub-install. Perhaps grub and grubby were updated,
but grub-install did not ran.
And after a "/sbin/grub-install /dev/sda", the default boot kernel
setting, made by grubby, started working. Another Scooby-Doo mystery
solved…
The current grub install command is grub2-install, but that is only run
for legacy boot environments, it is never used for uefi boots.
regards,
Steve
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10:58 p.m.
On Sat, 2023-01-07 at 20:40 -0500, Sam Varshavchik wrote:
Can anyone try using grubby --set-default to change the default boot
kernel
to something other than the most recently-installed kernel, successfully?
It tells me that it obeys my request, and grubby --info=DEFAULT shows that
the default boot kernel is what I specified.
But at boot the grub menu still highlights the most recently installed
kernel, and that's what boots by default.
As I recall, there was always several aspects to this.
Each menu stanza for the particular kernel you booted needed to have a
"set default" option set in it. So that when you picked that menu
option at boot time, it set the default variable to itself *and* *then*
booted that kernel. If you booted from a menu choice that didn't
include that option, it wouldn't set itself as the default for the next
boot. It was a per-stanza thing, not a once in the GRUB config, thing.
And at boot/reboot, GRUB had to be configured to read the default
variable to see which menu item to boot.
I lack the perseverance to read through the conglomeration of GRUB menu
files to see what it does these days.
--
uname -rsvp
Linux 3.10.0-1160.81.1.el7.x86_64 #1 SMP Fri Dec 16 17:29:43 UTC 2022 x86_64
Boilerplate: All unexpected mail to my mailbox is automatically deleted.
I will only get to see the messages that are posted to the mailing list.
1:46 a.m.
On 8/1/23 15:58, Tim via users wrote:
On Sat, 2023-01-07 at 20:40 -0500, Sam Varshavchik wrote:
> Can anyone try using grubby --set-default to change the default boot kernel
> to something other than the most recently-installed kernel, successfully?
>
> It tells me that it obeys my request, and grubby --info=DEFAULT shows that
> the default boot kernel is what I specified.
>
> But at boot the grub menu still highlights the most recently installed
> kernel, and that's what boots by default.
>
As I recall, there was always several aspects to this.
Each menu stanza for the particular kernel you booted needed to have a
"set default" option set in it. So that when you picked that menu
option at boot time, it set the default variable to itself *and* *then*
booted that kernel. If you booted from a menu choice that didn't
include that option, it wouldn't set itself as the default for the next
boot. It was a per-stanza thing, not a once in the GRUB config, thing.
And at boot/reboot, GRUB had to be configured to read the default
variable to see which menu item to boot.
I lack the perseverance to read through the conglomeration of GRUB menu
files to see what it does these days.
From a google check for the default grub kernel boots it seems that if
you add the following two statements into /etc/default/grub and then run
grub2-mkconfig grub will use the last selected kernel as the default
boot kernel.
|GRUB_SAVEDEFAULT=true GRUB_DEFAULT=saved|
regards,
Steve
2:57 a.m.
Hi
On Sun, 08 Jan 2023 18:46:09 +1100 Stephen Morris wrote:
From a google check for the default grub kernel boots it seems that
if
you add the following two statements into /etc/default/grub and then run
grub2-mkconfig grub will use the last selected kernel as the default
boot kernel.
|GRUB_SAVEDEFAULT=true GRUB_DEFAULT=saved|
Right: I do that since the switch to grub2.
In addition I add a script in /etc/kernel/postinst.d/ to force a
grub2-mkconfig at each new kernel install.
---------------------------------------------------------------
#!/bin/bash -p
PATH=/sbin:/bin:/usr/sbin:/usr/bin
# Regenerates grub.cfg in posttrans of a kernel installation.
date=$(date '+%Y-%m-%d_%H%M%S')
grub2conf=/boot/grub2/grub.cfg
cp -pf $grub2conf $grub2conf-$date
grub2-mkconfig -o $grub2conf || {
# grub2-mkconfig is safe: do not install if it fails.
echo '*** /sbin/grub2-mkconfig failed. Aborting'
exit 1
}
# Suppress the current saved_entry: potentially wrong since one
# rebuilds grub.cfg.
grub2-editenv - unset saved_entry
---------------------------------------------------------------
--
francis
10:54 a.m.
Stephen Morris writes:
>
And at boot/reboot, GRUB had to be configured to read the default
> variable to see which menu item to boot.
>
> I lack the perseverance to read through the conglomeration of GRUB menu
> files to see what it does these days.
>
From a google check for the default grub kernel boots it seems that if you
add the following two statements into /etc/default/grub and then run grub2-
mkconfig grub will use the last selected kernel as the default boot kernel.
GRUB_SAVEDEFAULT=true
GRUB_DEFAULT=saved
I have never diddled my /etc/default/grub. Currently it has only
GRUB_DEFAULT=saved
a bunch of other stuff, no explicit GRUB_SAVEDEFAULT=true. I wonder what
that ends up doing…
7:06 p.m.
On 9/1/23 03:54, Sam Varshavchik wrote:
Stephen Morris writes:
>> And at boot/reboot, GRUB had to be configured to read the default
>> variable to see which menu item to boot.
>>
>> I lack the perseverance to read through the conglomeration of GRUB menu
>> files to see what it does these days.
>>
> From a google check for the default grub kernel boots it seems that
> if you add the following two statements into /etc/default/grub and
> then run grub2-mkconfig grub will use the last selected kernel as the
> default boot kernel.
>
> GRUB_SAVEDEFAULT=true
> GRUB_DEFAULT=saved
I have never diddled my /etc/default/grub. Currently it has only
GRUB_DEFAULT=saved
a bunch of other stuff, no explicit GRUB_SAVEDEFAULT=true. I wonder
what that ends up doing…
My /etc/default/grub is the same. I only ever have 1
kernel entry in the
main menu section for Fedora and Ubuntu, the other kernels are in
sub-menus. When I boot the Fedora kernel is the first entry in the menu
and when the count down timer expires Fedora is booted. I am assuming
that if instead I booted into Ubuntu or Windows for that matter the
combination of the two statements would cause all subsequent boots to
boot either Ubuntu or Windows (depending on which one was booted in to)
until such time as a different menu entry was selected and then it would
become the default boot entry. Again from what I have read, these two
statements don't work if you have booted from a sub-menu, other steps
need to be taken to make that entry the default boot entry.
regards,
Steve
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4:36 a.m.
On 08/01/2023 01:40, Sam Varshavchik wrote:
Can anyone try using grubby --set-default to change the default boot
kernel to something other than the most recently-installed kernel,
successfully?
It tells me that it obeys my request, and grubby --info=DEFAULT shows
that the default boot kernel is what I specified.
But at boot the grub menu still highlights the most recently installed
kernel, and that's what boots by default.
What I do is this;
[root@armf37 ~]# grubby --info=ALL
index=0
kernel="/boot/vmlinuz-6.0.17-300.fc37.aarch64"
args="ro rootflags=subvol=root rhgb quiet"
root="UUID=2b7a3341-3b66-42c2-bc12-6c4d58c58957"
initrd="/boot/initramfs-6.0.17-300.fc37.aarch64.img"
title="Fedora Linux (6.0.17-300.fc37.aarch64) 37 (KDE Plasma)"
id="ce79604f5b5945f28b6a37ac66f4ffc4-6.0.17-300.fc37.aarch64"
index=1
kernel="/boot/vmlinuz-6.0.16-300.fc37.aarch64"
args="ro rootflags=subvol=root rhgb quiet"
root="UUID=2b7a3341-3b66-42c2-bc12-6c4d58c58957"
initrd="/boot/initramfs-6.0.16-300.fc37.aarch64.img"
title="Fedora Linux (6.0.16-300.fc37.aarch64) 37 (KDE Plasma)"
id="ce79604f5b5945f28b6a37ac66f4ffc4-6.0.16-300.fc37.aarch64"
index=2
kernel="/boot/vmlinuz-0-rescue-ce79604f5b5945f28b6a37ac66f4ffc4"
args="ro rootflags=subvol=root rhgb quiet"
root="UUID=2b7a3341-3b66-42c2-bc12-6c4d58c58957"
initrd="/boot/initramfs-0-rescue-ce79604f5b5945f28b6a37ac66f4ffc4.img"
title="Fedora Linux (0-rescue-ce79604f5b5945f28b6a37ac66f4ffc4) 36 (KDE
Plasma)"
id="ce79604f5b5945f28b6a37ac66f4ffc4-0-rescue"
Then I pick the kernel by index, because its easier to type:
[root@armf37 ~]# grubby --set-default-index=1
The default is
/boot/loader/entries/ce79604f5b5945f28b6a37ac66f4ffc4-6.0.16-300.fc37.aarch64.conf
with index 1 and kernel /boot/vmlinuz-6.0.16-300.fc3
7.aarch64
This has always worked for me.
But in testing this on my f37 upgraded from f36 index 1 flipped to
booting the f36 5.17 kernel!
That is not in the list above you will notice. I found that
/boot/grub2/grub.cfg had the 5.17
kernel in a menuentry section becuase of /etc/grub.d/10_linux (?!?!?!)
To fix that I did:
[root@armf37 ~]# grub2-mkconfig -o /boot/grub2/grub.cfg
To remove rhgb and quiet I do this:
[root@armf37 ~]# grubby --update-kernel=ALL --remove-args=rhgb\ quiet
[root@armf37 ~]# grubby --info=ALL
index=0
kernel="/boot/vmlinuz-6.0.17-300.fc37.aarch64"
args="ro rootflags=subvol=root"
root="UUID=2b7a3341-3b66-42c2-bc12-6c4d58c58957"
initrd="/boot/initramfs-6.0.17-300.fc37.aarch64.img"
title="Fedora Linux (6.0.17-300.fc37.aarch64) 37 (KDE Plasma)"
id="ce79604f5b5945f28b6a37ac66f4ffc4-6.0.17-300.fc37.aarch64"
index=1
kernel="/boot/vmlinuz-6.0.16-300.fc37.aarch64"
args="ro rootflags=subvol=root"
root="UUID=2b7a3341-3b66-42c2-bc12-6c4d58c58957"
initrd="/boot/initramfs-6.0.16-300.fc37.aarch64.img"
title="Fedora Linux (6.0.16-300.fc37.aarch64) 37 (KDE Plasma)"
id="ce79604f5b5945f28b6a37ac66f4ffc4-6.0.16-300.fc37.aarch64"
index=2
kernel="/boot/vmlinuz-0-rescue-ce79604f5b5945f28b6a37ac66f4ffc4"
args="ro rootflags=subvol=root"
root="UUID=2b7a3341-3b66-42c2-bc12-6c4d58c58957"
initrd="/boot/initramfs-0-rescue-ce79604f5b5945f28b6a37ac66f4ffc4.img"
title="Fedora Linux (0-rescue-ce79604f5b5945f28b6a37ac66f4ffc4) 36 (KDE
Plasma)"
id="ce79604f5b5945f28b6a37ac66f4ffc4-0-rescue"
Barry
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482
days inactive
483
days old
9 comments
6 participants
participants (6)
-
Barry Scott -
Francis.Montagnac＠inria.fr -
Sam Varshavchik -
Stephen Morris -
Tim -
Tom Horsley