[gentoo-user] Does root=PARTUUID=<> work with DOS partition table?

[gentoo-user] Does root=PARTUUID=<> work with DOS partition table?

[Grant Edwards]

I'm trying to install Gentoo with root on a USB SSD.  In order to
allow for varying enumeration order of USB block-storage devices, I've
configured grub to search for its root by using the filesystem label,
and that seems to work.

Since I'm not using an initrd, on the kernel command line I can't use
root=LABEL=<> or root=UUID=<>.  Right?

But, supposedly I can use root=PARTUUID=<>.

That doesn't seem to work.  The kernel always reports

   cannot open root device "PARTUUID=4e66c96c-01"

Where 4e66c96c-01 is the PARTUUID value shown by the blkid command.

I've tried a rootdelay of up to 20 seconds, and that doesn't seem to
help.

All the examples I can find of people using root=PARTUUID=<> show the
longer PARTUUID values you get with a GPT parition table.  Does the
root=PARTUUID=<> mechanism only work with GPT and not with DOS
parition tables?

-- 
Grant Edwards               grant.b.edwards        Yow! Okay ... I'm going
                                  at               home to write the "I HATE
                              gmail.com            RUBIK's CUBE HANDBOOK FOR
                                                   DEAD CAT LOVERS" ...

[gentoo-user] Re: Does root=PARTUUID=<> work with DOS partition table?

[Grant Edwards]

On 2019-07-25, Grant Edwards <grant.b.edwards@gmail.com> wrote:

> All the examples I can find of people using root=PARTUUID=<> show the
> longer PARTUUID values you get with a GPT parition table.  Does the
> root=PARTUUID=<> mechanism only work with GPT and not with DOS
> parition tables?

The comments in the kernel source certinaly indicate that DOS PARTUUID
values should work.  From init/do_mounts.c:

/*
 *	Convert a name into device number.  We accept the following variants:
[...]
 *	6) PARTUUID=00112233-4455-6677-8899-AABBCCDDEEFF representing the
 *	   unique id of a partition if the partition table provides it.
 *	   The UUID may be either an EFI/GPT UUID, or refer to an MSDOS
 *	   partition using the format SSSSSSSS-PP, where SSSSSSSS is a zero-
 *	   filled hex representation of the 32-bit "NT disk signature", and PP
 *	   is a zero-filled hex representation of the 1-based partition number.
 [...]

I've also tried just passing root=/dev/sdb1 (which in the current
setup is consistently the device the root partition shows up on).
That doesn't work either and I'm begining to suspect that the kernel
simply isn't recognizing the USB storage device at all.

I wish I could figure out how to get scrollback to work so I could see
all of the kernel messages before the panic...

-- 
Grant Edwards               grant.b.edwards        Yow! I think my career
                                  at               is ruined!
                              gmail.com            

Re: [gentoo-user] Re: Does root=PARTUUID=<> work with DOS partition table?

[Jack]

When you get the grub prompt, hit "e" for edit mode, or maybe better "c" 
for command line.  By typing "root (" and hitting tab, it should let you 
know what disks it sees.  If you're not sure which disk is which which, 
accept one (such as hd0) and then hit tab to see the partitions it sees.

Possible reasons (mainly pulled out of thin air) does the partition need 
the boot flag set?  do you need to specify rootfs type?

On 7/25/19 11:25 AM, Grant Edwards wrote:
> On 2019-07-25, Grant Edwards <grant.b.edwards@gmail.com> wrote:
>
>> All the examples I can find of people using root=PARTUUID=<> show the
>> longer PARTUUID values you get with a GPT parition table.  Does the
>> root=PARTUUID=<> mechanism only work with GPT and not with DOS
>> parition tables?
> The comments in the kernel source certinaly indicate that DOS PARTUUID
> values should work.  From init/do_mounts.c:
>
> /*
>   *	Convert a name into device number.  We accept the following variants:
> [...]
>   *	6) PARTUUID=00112233-4455-6677-8899-AABBCCDDEEFF representing the
>   *	   unique id of a partition if the partition table provides it.
>   *	   The UUID may be either an EFI/GPT UUID, or refer to an MSDOS
>   *	   partition using the format SSSSSSSS-PP, where SSSSSSSS is a zero-
>   *	   filled hex representation of the 32-bit "NT disk signature", and PP
>   *	   is a zero-filled hex representation of the 1-based partition number.
>   [...]
>
> I've also tried just passing root=/dev/sdb1 (which in the current
> setup is consistently the device the root partition shows up on).
> That doesn't work either and I'm begining to suspect that the kernel
> simply isn't recognizing the USB storage device at all.
>
> I wish I could figure out how to get scrollback to work so I could see
> all of the kernel messages before the panic...
>

Re: [gentoo-user] Re: Does root=PARTUUID=<> work with DOS partition table?

[Mike Gilbert]

On Thu, Jul 25, 2019 at 11:25 AM Grant Edwards
<grant.b.edwards@gmail.com> wrote:
>
> On 2019-07-25, Grant Edwards <grant.b.edwards@gmail.com> wrote:
>
> > All the examples I can find of people using root=PARTUUID=<> show the
> > longer PARTUUID values you get with a GPT parition table.  Does the
> > root=PARTUUID=<> mechanism only work with GPT and not with DOS
> > parition tables?
>
> The comments in the kernel source certinaly indicate that DOS PARTUUID
> values should work.  From init/do_mounts.c:
>
> /*
>  *      Convert a name into device number.  We accept the following variants:
> [...]
>  *      6) PARTUUID=00112233-4455-6677-8899-AABBCCDDEEFF representing the
>  *         unique id of a partition if the partition table provides it.
>  *         The UUID may be either an EFI/GPT UUID, or refer to an MSDOS
>  *         partition using the format SSSSSSSS-PP, where SSSSSSSS is a zero-
>  *         filled hex representation of the 32-bit "NT disk signature", and PP
>  *         is a zero-filled hex representation of the 1-based partition number.
>  [...]
>
> I've also tried just passing root=/dev/sdb1 (which in the current
> setup is consistently the device the root partition shows up on).
> That doesn't work either and I'm begining to suspect that the kernel
> simply isn't recognizing the USB storage device at all.
>
> I wish I could figure out how to get scrollback to work so I could see
> all of the kernel messages before the panic...

Do you have all the necessary USB drivers compiled into the kernel?
Check to make sure the following options are "y".

CONFIG_USB_EHCI_HCD -- USB 2.0
CONFIG_USB_OHCI_HCD -- USB 1.0 (non-Intel)
CONFIG_USB_UHCI_HCD -- USB 1.0 (Intel)
CONFIG_USB_XHCI_HCD -- USB 3.0

CONFIG_USB_STORAGE
CONFIG_BLK_DEV_SD

[gentoo-user] Re: Does root=PARTUUID=<> work with DOS partition table?

[Grant Edwards]

On 2019-07-25, Mike Gilbert <floppym@gentoo.org> wrote:

>> I've also tried just passing root=/dev/sdb1 (which in the current
>> setup is consistently the device the root partition shows up on).
>> That doesn't work either and I'm begining to suspect that the kernel
>> simply isn't recognizing the USB storage device at all.
[...]
> Do you have all the necessary USB drivers compiled into the kernel?
> Check to make sure the following options are "y".

Doh! I didn't have CONFIG_USB_XHCI_HCD enabled.

The kernel is now finding the root partition based on the DOS
paritition table verison of the PARTUUID.  Yay!

I'm a bit surprised that xhci support isn't enable by default these
days.  It's been yonks since you could buy a new machine that didn't
have an xhci controller, and presumably having support enabled on an
old machine doesn't cause problems.

The Intel wireless interface isn't showing up yet, because the
firmware loading is failing.  It worked when booting from the minimal
install image, so I've still got some kernel configuration tweaking to
do.  I have vague memories of the iwlwifi driver not working well when
compiled as part of the kernel but working better as a module...

-- 
Grant Edwards               grant.b.edwards        Yow! TAILFINS!! ... click
                                  at               ...
                              gmail.com