Re: [GRUB PARTUUID PATCH V10 4/4] Update grub script template files

[Daniel Kiper]

On Mon, Apr 16, 2018 at 10:36:26PM -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
>
> Note: GRUB_DISABLE_LINUX_PARTUUID and GRUB_DISABLE_LINUX_UUID equate to
>       'false' when unset or set to any value other than 'true'.
>       GRUB_DISABLE_LINUX_PARTUUID defaults to 'true'.
> Signed-off-by: Nicholas Vinson <address@hidden>
> ---
>  docs/grub.texi              | 67 ++++++++++++++++++++++++++++++++++---
>  util/grub-mkconfig.in       |  3 ++
>  util/grub.d/10_linux.in     | 22 ++++++++++--
>  util/grub.d/20_linux_xen.in | 22 ++++++++++--
>  4 files changed, 104 insertions(+), 10 deletions(-)
>
> diff --git a/docs/grub.texi b/docs/grub.texi
> index 0f2ab91fc..6aa65552f 100644
> --- a/docs/grub.texi
> +++ b/docs/grub.texi
> @@ -1214,10 +1214,11 @@ GRUB is configured using @file{grub.cfg}, usually 
> located under
>  need to write the whole thing by hand.
>
>  @menu
> -* Simple configuration::        Recommended for most users
> -* Shell-like scripting::        For power users and developers
> -* Multi-boot manual config::    For non-standard multi-OS scenarios
> -* Embedded configuration::      Embedding a configuration file into GRUB
> +* Simple configuration::            Recommended for most users
> +* Root Identifcation Heuristics::   Summary on how the root file system is 
> identified.
> +* Shell-like scripting::            For power users and developers
> +* Multi-boot manual config::        For non-standard multi-OS scenarios
> +* Embedded configuration::          Embedding a configuration file into GRUB
>  @end menu
>
>
> @@ -1425,6 +1426,17 @@ 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}.
>
> address@hidden GRUB_DISABLE_LINUX_PARTUUID
> +If @command{grub-mkconfig} cannot identify the root filesystem via its
> +universally-unique indentifier (UUID), @command{grub-mkconfig} can 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 @samp{GRUB_DISABLE_LINUX_PARTUUID} is set to
> address@hidden, the Linux kernel version must be 2.6.37 (3.10 for systems 
> using
> +the MSDOS partition scheme) or newer.  This option defaults to @samp{true}.  
> To
> +enable the use of partition UUIDs, set this option to @samp{false}.
> +
>  @item GRUB_DISABLE_RECOVERY
>  If this option is set to @samp{true}, disable the generation of recovery
>  mode menu entries.
> @@ -1556,6 +1568,53 @@ edit the scripts in @file{/etc/grub.d} directly.
>  menu entries; simply type the menu entries you want to add at the end of
>  that file, making sure to leave at least the first two lines intact.
>
> address@hidden Root Identifcation Heuristics
> address@hidden Root Identifcation Heuristics
> +If the target operating system uses the Linux kernel, @command{grub-mkconfig}
> +attempts to identify the root file system via a heuristic algoirthm.  This
> +algorithm selects the identification method of the root file system by
> +considering three factors.  The first is if an initrd for the target 
> operating
> +system is also present.  The second is @samp{GRUB_DISABLE_LINUX_UUID} and if 
> set
> +to @samp{true}, prevents @command{grub-mkconfig} from identifying the root 
> file
> +system by its UUID.  The third is @samp{GRUB_DISABLE_LINUX_PARTUUID} and if 
> set
> +to @samp{true}, prevents @command{grub-mkconfig} from identifying the root 
> file
> +system via the UUID of its enclosing partition.  If the variables are 
> assigned
> +any other value, that value is considered equivalent to @samp{false}.  The
> +variables are also considered to be set to @samp{false} if they are not set.
> +
> +When booting, the Linux kernel will delegate the task of mounting the root
> +filesystem to the initrd.  Most initrd images determine the root file system 
> by
> +checking the Linux kernel's command-line for the @samp{root} key and use its
> +value as the identification method of the root file system.  To improve the
> +reliability of booting, most initrd images also allow the root file system 
> to be
> +identified by its UUID.  Because of this behavior, the 
> @command{grub-mkconfig}
> +command will set @samp{root} to @samp{root=UUID=...} to provide the initrd 
> with
> +the filesystem UUID of the root file system.
> +
> +If no initrd is detected or @samp{GRUB_DISABLE_LINUX_UUID} is set then

s/set/set to @samp{true}/?

> address@hidden will identify the root filesystem by setting the kernel
> +command-line variable @samp{root} to @samp{root=PARTUUID=...} unless
> address@hidden is also set to @samp{true}.  If
> address@hidden is also set to @samp{true},
> address@hidden will identify by its LInux device name.

s/LInux/Linux/g

> +
> +The following table summarizes the behavior of the @command{grub-mkconfig}
> +command.
> +
> address@hidden {detected} {GRUB_DISABLE_LINUX_PARTUUID} 
> {GRUB_DISABLE_LINUX_UUID} {Linux Root}
> address@hidden Initrd detected @tab GRUB_DISABLE_LINUX_PARTUUID Set To @tab 
> GRUB_DISABLE_LINUX_UUID Set To @tab Linux Root ID Method
> address@hidden false         @tab false                       @tab false      
>              @tab part UUID
> address@hidden false         @tab false                       @tab true       
>              @tab part UUID

I hope that you have tested these two settings and they work. If yes then
I am happy with all the patches. If there are no objections I will commit
all of them in a week or so. I will fix both nitpicks listed above just
before commit.

Daniel