On Tue, Apr 17, 2018 at 08:20:45AM -0700, Nick Vinson wrote:
> On 04/17/2018 06:36 AM, Daniel Kiper wrote:
> > 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 <nvinson...@gmail.com>
> >> ---
> >> 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}.
> >>
> >> +@item 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
> >> +@samp{false}, 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.
> >>
> >> +@node Root Identifcation Heuristics
> >> +@section 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}/?
>
> Yes. Thanks.
>
> >
> >> +@command{grub-command} will identify the root filesystem by setting the
> >> kernel
> >> +command-line variable @samp{root} to @samp{root=PARTUUID=...} unless
> >> +@samp{GRUB_DISABLE_LINUX_PARTUUID} is also set to @samp{true}. If
> >> +@samp{GRUB_DISABLE_LINUX_PARTUUID} is also set to @samp{true},
> >> +@command{grub-command} will identify by its LInux device name.
> >
> > s/LInux/Linux/g
>
> ack.
>
> >
> >> +
> >> +The following table summarizes the behavior of the @command{grub-mkconfig}
> >> +command.
> >> +
> >> +@multitable {detected} {GRUB_DISABLE_LINUX_PARTUUID}
> >> {GRUB_DISABLE_LINUX_UUID} {Linux Root}
> >> +@headitem Initrd detected @tab GRUB_DISABLE_LINUX_PARTUUID Set To @tab
> >> GRUB_DISABLE_LINUX_UUID Set To @tab Linux Root ID Method
> >> +@item false @tab false @tab false
> >> @tab part UUID
> >> +@item 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.
>
> I did. I've added a test script and its output at the bottom of this email.
LGTM, thank you for doing the work.
Daniel
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