Re: [PATCH] Add config option to prefer Linux kernel versions by substring match

[Doug Brunner <doug@doug-brunner.com>]

> On Sun, Sep 7, 2014 at 12:37 PM, Doug Brunner <doug@doug-brunner.com> wrote:
>> Hi all,
>>
>> First time submitting - please let me know if I'm doing anything wrong.
>>
>> This patch adds an option, GRUB_LINUX_PREF_VERSION_SUBSTR, that can be set to prioritize Linux kernels containing a
>> given substring. This takes precedence over version ordering, so if you have 3.14.1-generic, 3.14.2-generic,
>> 3.8.13-fnord1, and 3.8.13-fnord2 and the substring is 'fnord', the order is:
>> 3.8.13-fnord2
>> 3.8.13-fnord1
>> 3.14.2-generic
>> 3.14.1-generic
>>
>> Rationale: I and others, (see e.g. http://askubuntu.com/questions/216398/set-older-kernel-as-default-grub-entry) needed
>> to change the Linux kernel version GRUB sets as default. The process is error-prone: you have to figure out where in the
>> GRUB menu it will appear, then enter that in /etc/default/grub, and if the menu position changes due to new kernels
>> added to the system you have to do it all over again. I had older kernels with a distinctive local version naming scheme
>> that I wanted preferred over the stock kernels, but it could also be used to specify a particular kernel version.
> 
> Your rationale, as stated, is completely solved by using the menuentry
> ID, as documented in "info -f grub -n 'Simple configuration' ", rather
> than using a menuentry number. The answer given to that askubuntu.com
> question is a poor one, as noted by one of the commentors (though that
> commenter recommends menuentry titles, which have their own issues,
> again as documented in the texinfo manual).
> 
I think there would still be some usability gains; if I understand it correctly, to use menuentry IDs, I would have to
enter e.g. 'gnulinux-advanced-UUID>gnulinux-3.8.13-fnord1-advanced-UUID', where UUID is for my root partition. This is
still somewhat laborious to compose; for my use case, it also requires redoing the entry every time I build a new -fnord
kernel.

If I can come up with a way of making GRUB_DEFAULT use a substring match rather than exact match (in the case of
multiple matches, perhaps choosing the latest kernel version that matches) would that be acceptable?

Doug Brunner