Boot order use the oldest kernel

[Jon Ingason]

Hi,
With one of my computers I have problem to set permanent default start
order of the kernel. I can change it with "sudo grub2-set-default 0" but
when I update the kernel I get oldest kernel as default boot order.
How do I make the start order so the latest kernel is default?
-- 
Regards

Jon Ingason

[sixpack13]

/etc/default/grub 
is used during kernel updates

there GRUB_DEFAULT= should be 0 or saved (I guess it's the default after fresh OS
install)

GRUB_DEFAULT=saved 
reads /boot/grub2/grubenv

- if I get that right -

[sixpack13]

s/reads/is related to/

[Tim]

On Mon, 2019-10-07 at 23:02 +0000,   sixpack13 wrote:
>  /etc/default/grub 
>  is used during kernel updates
>  
>  there GRUB_DEFAULT= should be 0 or saved (I guess it's the default
>  after fresh OS install)
>  
>  GRUB_DEFAULT=saved 
>  reads /boot/grub2/grubenv
>  
>  - if I get that right -  
The default = saved option would make the next boot use the last kernel
that you selected.  However, it depends on each stanza saving itself as
the one to be used.  Zero means to boot from the topmost stanza
(usually new kernels are written to the top of the list, so zero picks
the latest).

i.e. You have three kernels to choose from, each grub entry for that
kernel saves its choice when selected, then boots up.  Next boot up,
grub looks to see what grub entry number was saved, and boots it.

Taking part of grub.conf from very old system of mine as an example:

default saved

title Fedora Core (2.6.17-1.2142_FC4)
        root (hd0,0)
        kernel /vmlinuz-2.6.17-1.2142_FC4 ro root=LABEL=/ acpi=force
        initrd /initrd-2.6.17-1.2142_FC4.img
        savedefault

title Fedora Core (2.6.17-1.2139_FC4)
        root (hd0,0)
        kernel /vmlinuz-2.6.17-1.2139_FC4 ro root=LABEL=/ acpi=force
        initrd /initrd-2.6.17-1.2139_FC4.img
        savedefault

title Fedora Core (2.6.16-1.2111_FC4)
        root (hd0,0)
        kernel /vmlinuz-2.6.16-1.2111_FC4 ro root=LABEL=/ acpi=force
        initrd /initrd-2.6.16-1.2111_FC4.img

At the beginning is the "default saved" command that tells grub to boot
using the same kernel as last time.  However, only the first two
entries save themselves as the default.  If I elect to boot from the
third kernel (last on the list), I'm not sure what would happen next
boot.  I'm guessing that whichever out of the first two I last used
would be booted, because one of them set themselves as default, and
nothing else unsets that.

NB: I'm not sure if "savedefault" has to be last, or can be typed
anywhere in the stanzas.  And I'd be very surprised if the modern grub
didn't behave in the same way (having to deliberately save the chosen
entry as the default), but it installed no man file, nor a useful info
file on the PC that I'm looking at.

-- 
 
uname -rsvp
Linux 3.10.0-1062.1.2.el7.x86_64 #1 SMP Mon Sep 30 14:19:46 UTC 2019 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.

[Jon Ingason]

Den 2019-10-08 kl. 06:39, skrev Tim via users:
>  On Mon, 2019-10-07 at 23:02 +0000,   sixpack13 wrote:
> > /etc/default/grub 
> > is used during kernel updates
> >
> > there GRUB_DEFAULT= should be 0 or saved (I guess it's the default
> > after fresh OS install) 
My /etc/default/grub is:

$ more /etc/default/grub
GRUB_TIMEOUT=5
GRUB_DISTRIBUTOR="$(sed 's, release .*$,,g' /etc/system-release)"
GRUB_DEFAULT=saved
GRUB_DISABLE_SUBMENU=true
GRUB_TERMINAL_OUTPUT="console"
GRUB_CMDLINE_LINUX="resume=/dev/mapper/fedora_lea00-swap
rd.lvm.lv=fedora_lea00/
root rd.lvm.lv=fedora_lea00/swap rhgb quiet"
GRUB_DISABLE_RECOVERY="true"
GRUB_ENABLE_BLSCFG=true

So here is GRUB_DEFAULT=saved.

> >
> > GRUB_DEFAULT=saved 
> > reads /boot/grub2/grubenv
> >
> > - if I get that right -  
Latest kernel is 5.2.17-200.fc30.x86_64

My /boot/grub2/grubenv is:

$ sudo more /boot/grub2/grubenv
# GRUB Environment Block
saved_entry=f7addef1929b4033b5d242667945cf04-5.2.17-200.fc30.x86_64
boot_success=1
boot_indeterminate=0
kernelopts=root=/dev/mapper/fedora_lea00-root ro
resume=/dev/mapper/fedora_lea00
-swap rd.lvm.lv=fedora_lea00/root rd.lvm.lv=fedora_lea00/swap rhgb quiet
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-- Regards

Jon Ingason

[sixpack13]

@Tim thanks for clarification !

@Jon

set in /etc/default/grub 
GRUB_DEFAULT=0

and  run 

[ -d /sys/firmware/efi/efivars ] && sudo grub2-mkconfig -o
/boot/efi/EFI/fedora/grub.cfg || sudo grub2-mkconfig -o /boot/grub2/grub.cfg

[Jon Ingason]

Den 2019-10-08 kl. 19:57, skrev sixpack13:
>  @Tim thanks for clarification !
>  
>  @Jon
>  
>  set in /etc/default/grub 
>  GRUB_DEFAULT=0
>  
>  and  run 
>  
>  [ -d /sys/firmware/efi/efivars ] && sudo grub2-mkconfig -o
> /boot/efi/EFI/fedora/grub.cfg || sudo grub2-mkconfig -o /boot/grub2/grub.cfg
>   
Thanks sixpack13 I will test this.

-- 
Regards

Jon Ingason