Re: [PATCH] Add support for specifying the boot device by label

[darkpenguin]

>> 3) I could not figure out how to source other variables from
>> /etc/defaults/grub and why not all of them are there. :)
>>
> 
> This looks to be in util/grub-mkconfig.in (lines 160-162 in git master
> at the time of writing):
> 
>     if test -f ${sysconfdir}/default/grub ; then
>       . ${sysconfdir}/default/grub
>     fi
> 
> The vars then get exported further down (lines 213-258) before running
> the various config snippets:
> 
>     # These are optional, user-defined variables.
>     export GRUB_DEFAULT \
>       GRUB_HIDDEN_TIMEOUT \
>       GRUB_HIDDEN_TIMEOUT_QUIET \
>       GRUB_TIMEOUT \
>       GRUB_TIMEOUT_STYLE \
>       GRUB_DEFAULT_BUTTON \
>     # ... snip ...

Thanks for the explanation about the vars! I've found it.


>> The decision to reuse GRUB_DISABLE_LINUX_UUID was because:
>> 1) This is more of an addition on top of UUID rather than "disabling"
>> it, it still uses UUID internally, and it falls back to UUID
>> 2) I could not come up with a better way to do it
>
> I'm not a fan of overloading a "disable" var to mean "try something
> else first". Something like GRUB_DISABLE_LINUX_LABEL with the
> appropriate logic would make more sense IMO.

Then how should we do it? I wouldn't want this to be the default
behaviour - it's only useful in specific cases, so I think
GRUB_DISABLE_LINUX_LABEL is a bad idea. So then we have
GRUB_DISABLE_LINUX_UUID and GRUB_ENABLE_TRYING_LABEL_BEFORE_UUID, which
requires not disabling UUID. This looks much more like a mess.

My reasoning was: previously, we had two modes - "use UUID" and "don't
use UUID". Now we are introducing a third more - "try labels, then use
UUID". It feels like the mode should be controlled by one variable that
accepts one of three possible values. Since renaming the variable to
GRUB_LINUX_MODE would be too much of a breaking change, maybe we should
just make the old one accept one of three possible values?
- true - enable UUID
- LABEL - enable UUID, but try labels on top of UUID first
- anything else - don't use UUID

Maybe later we can figure out the best way to do this based on feedback,
but to minimize change when introducing a proof-of-concept feature, this
seems more appropriate, doesn't it?