Re: [GRUB PARTUUID PATCH V9 4/5] Update grub script template files

[Nick Vinson <nvinson234@gmail.com>]

On 04/11/2018 01:31 AM, Daniel Kiper wrote:
> On Tue, Apr 10, 2018 at 08:00:04PM -0700, Nick Vinson wrote:
>> On 04/10/2018 01:52 PM, Daniel Kiper wrote:
>>> On Sat, Apr 07, 2018 at 04:28:13PM -0700, Nicholas Vinson wrote:
>>>> Update grub-mkconfig.in and 10_linux.in to support grub-probe's new
>>>> partuuid target.  Update grub.texi documentation.  The following table
>>>> shows how GRUB_DISABLE_LINUX_UUID, GRUB_DISABLE_LINUX_PARTUUID, and
>>>> initramfs detection interact:
>>>>
>>>> Initramfs  GRUB_DISABLE_LINUX_PARTUUID  GRUB_DISABLE_LINUX_UUID  Linux Root
>>>> detected   Set                          Set                      ID Method
>>>>
>>>> False      False                        False                    part UUID
>>>> False      False                        True                     part UUID
>>>> False      True                         False                    dev name
>>>> False      True                         True                     dev name
>>>> True       False                        False                    fs UUID
>>>> True       False                        True                     part UUID
>>>> True       True                         False                    fs UUID
>>>> True       True                         True                     dev name
>>>
>>> What will happen if GRUB_DISABLE_LINUX_PARTUUID and/or GRUB_DISABLE_LINUX_UUID
>>> are not set? I think that you can avoid that by setting defaults. You do that
>>> for GRUB_DISABLE_LINUX_PARTUUID in next patch but GRUB_DISABLE_LINUX_UUID
>>> does not have any default.
>>>
>>
>> If they're not set, then that's the same as them being set to 'False'.
>> I should have worded my table above a bit differently and used Yes/No
>> instead of True/False as that is really what it is trying to convey.
> 
> IMO it will be more confusing. I think that I would use lowercase
> false/true as it is used in the script and below the table I would
> add a note that <VARIABLE_UNSET> == false or something like that.

Ack.  I will update the commit comment.

> 
>> I.E. If there is no initramfs detected and GRUB_DISABLE_LINUX_PARTUUID
>> is not set and GRUB_DISABLE_LINUX_UUID is not set, set the kernel root
>> variable to "root=PARTUUID=...".
>>
>> In the scripts, the only value explicitly checked for is 'true'.
>> Anything else (including unset) is considered false.
> 
> OK, perfect!
> 
>>>> Signed-off-by: Nicholas Vinson <nvinson234@gmail.com>
>>>> ---
>>>>  docs/grub.texi          | 10 ++++++++++
>>>>  util/grub-mkconfig.in   |  3 +++
>>>>  util/grub.d/10_linux.in | 18 +++++++++++++++---
>>>
>>> Could you update util/grub.d/20_linux_xen.in too?
>>
>> Let me see what I can do.  I have never worked with xen before, so I do
>> not know much about it.
> 
> This should be easy. However, if you are not sure please drop me a line.
> 
>>>>  3 files changed, 28 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/docs/grub.texi b/docs/grub.texi
>>>> index 65b4bbeda..06f0afe45 100644
>>>> --- a/docs/grub.texi
>>>> +++ b/docs/grub.texi
>>>> @@ -1424,6 +1424,16 @@ the Linux kernel, using a @samp{root=UUID=...} kernel parameter.  This is
>>>>  usually more reliable, but in some cases it may not be appropriate.  To
>>>>  disable the use of UUIDs, set this option to @samp{true}.
>>>>
>>>> +@item GRUB_DISABLE_LINUX_PARTUUID
>>>> +If @command{grub-mkconfig} cannot identify the root filesystem via its
>>>> +universally-unique indentifier (UUID), @command{grub-mkconfig} will use the UUID
>>>> +of the partition containing the filesystem to identify the root filesystem to
>>>> +the Linux kernel via a @samp{root=PARTUUID=...} kernel parameter.  This is not
>>>> +as reliable as using the filesystem UUID, but is more reliable than using the
>>>> +Linux device names.  When enabled, this option requires the Linux kernel version
>>>
>>> s/When enabled, /When enabled, GRUB_DISABLE_LINUX_PARTUUID set to false, /
>>> or something like that. Otherwise it is unclear.
>>
>> I'll clean up the wording in the next release.
> 
> Thanks a lot!
> 
> By the way, should not we merge patches 4 and 5 into one patch?

We should.

I split it so that if #5 proved controversial for some reason and
received a lot of resistance, it could be dropped and the remainder of
the patchset could be merged.

There does not seem to be any issue with setting
GRUB_DISABLE_LINUX_PARTUUID to a default value, so there is no reason to
keep it separate.

Thanks,
Nicholas Vinson

> 
> Daniel
>