I've built a custom kernel on a Debian 8 machine, and I want to set it as the default. A seemingly simple task, but I can't get it to work for the life of me.
I built my kernel using the official source code (via git), not using the vendor tarball provided my debian. Once built, I installed the kernel and modules with:
$ sudo make modules_install install
This installed a new menu entry into grub, which indeed works if you manually select it at boot time. So that's good.
Now, to get this to boot by default, I must edit /etc/default/grub and change GRUB_DEFAULT. At the top of the file is a comment pointing the user to an info page, which says:
'GRUB_DEFAULT'
The default menu entry. This may be a number, in which case it
identifies the Nth entry in the generated menu counted from zero,
or the title of a menu entry, or the special string 'saved'. Using
the id may be useful if you want to set a menu entry as the default
even though there may be a variable number of entries before it.
For example, if you have:
menuentry 'Example GNU/Linux distribution' --class gnu-linux --id example-gnu-linux {
...
}
then you can make this the default using:
GRUB_DEFAULT=example-gnu-linux
Previously it was documented the way to use entry title. While
this still works it's not recommended since titles often contain
unstable device names and may be translated
If you set this to 'saved', then the default menu entry will be
that saved by 'GRUB_SAVEDEFAULT' or 'grub-set-default'. This
relies on the environment block, which may not be available in all
situations (*note Environment block::).
The default is '0'.
First, it's unclear from the prose if an "id" is the same as a "title". That aside, it looks like I should use the string after the --id in the generated grub config.
So, make install inserted the following into /boot/grub/grub.cfg:
menuentry 'Debian GNU/Linux, with Linux 3.16.36krunsystickless+' --class debian --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-3.16.36krunsystickless+-advanced-197f20c1-1808-41b5-831f-b85a40358757' {
load_video
insmod gzio
if [ x$grub_platform = xxen ]; then insmod xzio; insmod lzopio; fi
insmod part_msdos
insmod ext2
set root='hd0,msdos1'
if [ x$feature_platform_search_hint = xy ]; then
search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 197f20c1-1808-41b5
-831f-b85a40358757
else
search --no-floppy --fs-uuid --set=root 197f20c1-1808-41b5-831f-b85a40358757
fi
echo 'Loading Linux 3.16.36krunsystickless+ ...'
linux /boot/vmlinuz-3.16.36krunsystickless+ root=UUID=197f20c1-1808-41b5-831f-b85a40358757 ro quiet console=ttyS0,115200n8 intel_psta
te=disable
echo 'Loading initial ramdisk ...'
initrd /boot/initrd.img-3.16.36krunsystickless+
}
Where, earlier in the file $menuentry_id_option is set:
if [ x"${feature_menuentry_id}" = xy ]; then
menuentry_id_option="--id"
else
menuentry_id_option=""
fi
So presumably, I should set GRUB_DEFAULT in /etc/grub/default to:
gnulinux-3.16.36krunsystickless+-advanced-197f20c1-1808-41b5-831f-b85a40358757
Then run:
$ sudo update-grub
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-3.16.36softdevnohzfullall
Found initrd image: /boot/initrd.img-3.16.36softdevnohzfullall
Found linux image: /boot/vmlinuz-3.16.36krunsystickless+
Found initrd image: /boot/initrd.img-3.16.36krunsystickless+
Found linux image: /boot/vmlinuz-3.16.36krunsystickless+.old
Found initrd image: /boot/initrd.img-3.16.36krunsystickless+
Found linux image: /boot/vmlinuz-3.16.0-4-amd64
Found initrd image: /boot/initrd.img-3.16.0-4-amd64
done
Before finally rebooting.
But this does not seem to work. The same kernel as before is instead booted. Does anyone know why?
Other things I have tried:
- Numeric index
GRUB_DEFAULTS-- seem to have no effect. - Escaping the plus in the kernel id.
grub-set-default
I'm going to look into feature_menuentry_id now, but I have a feeling it will be a red herring. If anyone can put me out of my misery in the meantime, I will be most grateful.
Thanks
