[gentoo-user] Can't find init due to inconsistent drive order

[gentoo-user] Can't find init due to inconsistent drive order

[Grant Edwards]

I've just recently run into a problem where sometimes when a machine
boots, the kernel can't find init.  This appears to be because my grub
configuration line says "root=/dev/sda5" and _sometimes_ the drive
that contains my root partition is sdb instead of sda. AFAICT, for the
past 30 years the linux kernel was 100% consistent in the order that
hard drives were labelled -- but recently that has seems to have
changed.

I use partition labels in my fstab, so that's not a problem, but after
all these years, the kernel still doesn't know how to grok parition
labels.

Are we really expected now to set up an initrd just so that the kernel
can find the root partition??

-- 
Grant Edwards               grant.b.edwards        Yow! I wonder if I could
                                  at               ever get started in the
                              gmail.com            credit world?

Re: [gentoo-user] Can't find init due to inconsistent drive order

[Paul Hartman]

On Mon, Jul 1, 2013 at 4:52 PM, Grant Edwards <grant.b.edwards@gmail.com> wrote:
> I've just recently run into a problem where sometimes when a machine
> boots, the kernel can't find init.  This appears to be because my grub
> configuration line says "root=/dev/sda5" and _sometimes_ the drive
> that contains my root partition is sdb instead of sda. AFAICT, for the
> past 30 years the linux kernel was 100% consistent in the order that
> hard drives were labelled -- but recently that has seems to have
> changed.

I wonder if it could be related to parallel initialization of disks. I
think there's a kernel toggle for that. I wonder if sometimes one
drive spins up faster than the other. (If that's even how it works...)

I have experienced situations where the drive names change depending
on what devices were plugged into the computer when it was turned on,
especially external hard drives, card readers or flash drives, or if a
disc in the CDROM drive. Not sure if that is due to the way the
computer's BIOS handled things during POST, or the way the linux
kernel does its thing.

> Are we really expected now to set up an initrd just so that the kernel
> can find the root partition??

As far as I know, the answer is "yes".

FWIW, I always resisted making an initrd until very recently, but
wanted to use UUID in my bootup on my new system. I used this command
(which I re-run whenever I deploy a new kernel):

dracut -H -o i18n -o resume -o usrmount --force /boot/initramfs.img

And then added one line to my grub2 config:

initrd  /initramfs.img

and it just simply works... though it's still a bit of black magic to
me, and every time I reboot I feel a bit of nervousness when I see
"Loading initial ramdisk..." and don't breathe until it succeeds. :)

Re: [gentoo-user] Can't find init due to inconsistent drive order

[Alan McKinnon]

On 01/07/2013 23:52, Grant Edwards wrote:
> I've just recently run into a problem where sometimes when a machine
> boots, the kernel can't find init.  This appears to be because my grub
> configuration line says "root=/dev/sda5" and _sometimes_ the drive
> that contains my root partition is sdb instead of sda. AFAICT, for the
> past 30 years the linux kernel was 100% consistent in the order that
> hard drives were labelled -- but recently that has seems to have
> changed.
> 
> I use partition labels in my fstab, so that's not a problem, but after
> all these years, the kernel still doesn't know how to grok parition
> labels.
> 
> Are we really expected now to set up an initrd just so that the kernel
> can find the root partition??
> 


Where have you been for the past 6 months?

Did you miss the entire clusterfuck debate about latest udev tricks?

Those names depend only on the order in which devices are discovered,
and that process has always been indeterminate. udev used to get in the
middle and rename things in an arbitrary but defined order, it no longer
does this.

We discussed this whole subject *to death* over the last many months



-- 
Alan McKinnon
alan.mckinnon@gmail.com

[gentoo-user] Re: Can't find init due to inconsistent drive order

[Grant Edwards]

On 2013-07-01, Alan McKinnon <alan.mckinnon@gmail.com> wrote:
> On 01/07/2013 23:52, Grant Edwards wrote:
>> I've just recently run into a problem where sometimes when a machine
>> boots, the kernel can't find init.  This appears to be because my grub
>> configuration line says "root=/dev/sda5" and _sometimes_ the drive
>> that contains my root partition is sdb instead of sda. AFAICT, for the
>> past 30 years the linux kernel was 100% consistent in the order that
>> hard drives were labelled -- but recently that has seems to have
>> changed.
>> 
>> I use partition labels in my fstab, so that's not a problem, but after
>> all these years, the kernel still doesn't know how to grok parition
>> labels.
>> 
>> Are we really expected now to set up an initrd just so that the kernel
>> can find the root partition??
>
> Where have you been for the past 6 months?
>
> Did you miss the entire clusterfuck debate about latest udev tricks?

No.

> Those names depend only on the order in which devices are discovered,
> and that process has always been indeterminate.

Really?  I've been running Linux on a lot of machines for 30 years --
often on machines with a half-dozen hard drives -- and I never saw
drive order change from one reboot to the next until today.  That's
quite a lucky streak.

> udev used to get in the middle and rename things in an arbitrary but
> defined order, it no longer does this.

How did udev get in the middle?  It somehow ran before the kernel
mounted root and started 'init'?

> We discussed this whole subject *to death* over the last many months

I remember that discussion, but I don't see how it's relelvent to
events that occur before init starts.

-- 
Grant

[gentoo-user] Re: Can't find init due to inconsistent drive order

[Grant Edwards]

On 2013-07-01, Paul Hartman <paul.hartman+gentoo@gmail.com> wrote:
> On Mon, Jul 1, 2013 at 4:52 PM, Grant Edwards <grant.b.edwards@gmail.com> wrote:
>> I've just recently run into a problem where sometimes when a machine
>> boots, the kernel can't find init.  This appears to be because my grub
>> configuration line says "root=/dev/sda5" and _sometimes_ the drive
>> that contains my root partition is sdb instead of sda. AFAICT, for the
>> past 30 years the linux kernel was 100% consistent in the order that
>> hard drives were labelled -- but recently that has seems to have
>> changed.
>
> I wonder if it could be related to parallel initialization of disks.

Apparently so.

> I think there's a kernel toggle for that.

I'll look into it.

>> Are we really expected now to set up an initrd just so that the
>> kernel can find the root partition??
>
> As far as I know, the answer is "yes".
>
> FWIW, I always resisted making an initrd until very recently, but
> wanted to use UUID in my bootup on my new system. I used this command
> (which I re-run whenever I deploy a new kernel):
>
> dracut -H -o i18n -o resume -o usrmount --force /boot/initramfs.img
>
> And then added one line to my grub2 config:
>
> initrd  /initramfs.img
>
> and it just simply works... though it's still a bit of black magic to
> me,

It's not really that complex.  There are two ways to get the kernel to
use an initial ram fs as root: the bootloader loads the initial ram
image into ram or it gets linked into the kernel when the kernel is
built.

> and every time I reboot I feel a bit of nervousness when I see
> "Loading initial ramdisk..." and don't breathe until it succeeds. :)

I've got nothing against initramfs -- on my embedded systems root
starts out as an initramfs and stays that way.  I just don't see why I
should be forced to have one.

-- 
Grant

Re: [gentoo-user] Re: Can't find init due to inconsistent drive order

[Canek Peláez Valdés]

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On Jul 1, 2013 9:45 PM, "Grant Edwards" <grant.b.edwards@gmail.com> wrote:
>
> On 2013-07-01, Alan McKinnon <alan.mckinnon@gmail.com> wrote:
> > On 01/07/2013 23:52, Grant Edwards wrote:
> >> I've just recently run into a problem where sometimes when a machine
> >> boots, the kernel can't find init.  This appears to be because my grub
> >> configuration line says "root=/dev/sda5" and _sometimes_ the drive
> >> that contains my root partition is sdb instead of sda. AFAICT, for the
> >> past 30 years the linux kernel was 100% consistent in the order that
> >> hard drives were labelled -- but recently that has seems to have
> >> changed.
> >>
> >> I use partition labels in my fstab, so that's not a problem, but after
> >> all these years, the kernel still doesn't know how to grok parition
> >> labels.
> >>
> >> Are we really expected now to set up an initrd just so that the kernel
> >> can find the root partition??
> >
> > Where have you been for the past 6 months?
> >
> > Did you miss the entire clusterfuck debate about latest udev tricks?
>
> No.
>
> > Those names depend only on the order in which devices are discovered,
> > and that process has always been indeterminate.
>
> Really?  I've been running Linux on a lot of machines for 30 years --
> often on machines with a half-dozen hard drives -- and I never saw
> drive order change from one reboot to the next until today.  That's
> quite a lucky streak.

Since Linus started writing Linux in 1991 (22 years ago), I want to know
which time machine did you use.

Regards.
--
Canek Peláez Valdés

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[gentoo-user] Re: Can't find init due to inconsistent drive order

[Grant Edwards]

On 2013-07-02, Canek Pel??ez Vald??s <caneko@gmail.com> wrote:
> On Jul 1, 2013 9:45 PM, "Grant Edwards" <grant.b.edwards@gmail.com> wrote:

>>> Those names depend only on the order in which devices are discovered,
>>> and that process has always been indeterminate.
>>
>> Really?  I've been running Linux on a lot of machines for 30 years --
>> often on machines with a half-dozen hard drives -- and I never saw
>> drive order change from one reboot to the next until today.  That's
>> quite a lucky streak.
>
> Since Linus started writing Linux in 1991 (22 years ago), I want to know
> which time machine did you use.

Doh! I meant 20 years.  The first time was just a typo, and then
somehow after reading my original post I did it again.

I started running Linux in 93 with a friend's Yggdrasil CD and a Sun
CD drive I borrowed from work.  I think that was on a 25MHz 486 with
4MB of RAM and two 30MB hard drives.

-- 
Grant

Re: [gentoo-user] Can't find init due to inconsistent drive order

[Stroller]

On 1 July 2013, at 23:57, Alan McKinnon wrote:
> ...
> Did you miss the entire clusterfuck debate about latest udev tricks?
> 
> Those names depend only on the order in which devices are discovered,
> and that process has always been indeterminate. udev used to get in the
> middle and rename things in an arbitrary but defined order, it no longer
> does this.

I though this applied only to network interfaces, not to hard-disks??!?!?!?

Stroller.

[gentoo-user] Re: Can't find init due to inconsistent drive order

[Grant Edwards]

On 2013-07-01, Grant Edwards <grant.b.edwards@gmail.com> wrote:

> I've just recently run into a problem where sometimes when a machine
> boots, the kernel can't find init.  This appears to be because my grub
> configuration line says "root=/dev/sda5" and _sometimes_ the drive
> that contains my root partition is sdb instead of sda. AFAICT, for the
> past 30 years the linux kernel was 100% consistent in the order that
> hard drives were labelled -- but recently that has seems to have
> changed.

I still haven't figured out why my drives suddenly started getting
discovered in varying orders.  I think that the SATA drives are always
in the same order with respect to each other, but sometimes the
external firewire drive gets discovered before the SATA drives and
sometimes after the SATA drives.

It looks like my options are:

 1) Keep hitting the reset button until it works.

 2) Unplug or power down the firewire drive when booting. 

 3) Set up an initrd for the sole purpose of finding the actual root
    parition via filesystem label.  [I find this idea rather offensive.]

 4) Build the firewire drive as a module instead of building it into
    the kernel.  That would delay the discovery of the firewire drive
    until after root has been mounted.

 5) For the drive with the root parition on it switch from a DOS
    parition table to a GPT partition table and use the
    root=PARTUUID=<whatever> kernel option.

 6) Fix the kernel so it can find root by looking at filesystem
    labels.

Number 6 (fixing the kernel) is The Right Thing To Do(tm), but it's a
bit out of scope for the momement.  The "early code" in the kernel
obviously knows how to read partition tables and also knows about the
relevent file system, so I'm a bit baffled why it can't look at the
file system label.
    
Changing the firewire driver to be a module is probably the simplest
solution, but it's a kludgy work-around for what is, in my opinion, a
kernel bug: if you are going to require people to specify an absolute
disk drive index for the root partition, then you'd better index
drives in a consistent order from one boot to the next.

Switching to a GPT partition table sounds like the cleanest solution,
but I need to figure out if the grub (legacy) ebuild includes GPT
support or not.  I know it's supported by grub2, but I don't really
feel like switching to grub2 ATM.
    
-- 
Grant Edwards               grant.b.edwards        Yow! But was he mature
                                  at               enough last night at the
                              gmail.com            lesbian masquerade?

Re: [gentoo-user] Re: Can't find init due to inconsistent drive order

[Randolph Maaßen]

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2013/7/2 Grant Edwards <grant.b.edwards@gmail.com>

> On 2013-07-01, Grant Edwards <grant.b.edwards@gmail.com> wrote:
>
> > I've just recently run into a problem where sometimes when a machine
> > boots, the kernel can't find init.  This appears to be because my grub
> > configuration line says "root=/dev/sda5" and _sometimes_ the drive
> > that contains my root partition is sdb instead of sda. AFAICT, for the
> > past 30 years the linux kernel was 100% consistent in the order that
> > hard drives were labelled -- but recently that has seems to have
> > changed.
>
> I still haven't figured out why my drives suddenly started getting
> discovered in varying orders.  I think that the SATA drives are always
> in the same order with respect to each other, but sometimes the
> external firewire drive gets discovered before the SATA drives and
> sometimes after the SATA drives.
>
> It looks like my options are:
>
>  1) Keep hitting the reset button until it works.
>
>  2) Unplug or power down the firewire drive when booting.
>
>  3) Set up an initrd for the sole purpose of finding the actual root
>     parition via filesystem label.  [I find this idea rather offensive.]
>
>  4) Build the firewire drive as a module instead of building it into
>     the kernel.  That would delay the discovery of the firewire drive
>     until after root has been mounted.
>
>  5) For the drive with the root parition on it switch from a DOS
>     parition table to a GPT partition table and use the
>     root=PARTUUID=<whatever> kernel option.
>
>
You don't need to switch to GPT for that. I have a DOS partitioned disk and
"blkid" prints the LABEL and UUID for each partition.


>  6) Fix the kernel so it can find root by looking at filesystem
>     labels.
>
> Number 6 (fixing the kernel) is The Right Thing To Do(tm), but it's a
> bit out of scope for the momement.  The "early code" in the kernel
> obviously knows how to read partition tables and also knows about the
> relevent file system, so I'm a bit baffled why it can't look at the
> file system label.
>
> Changing the firewire driver to be a module is probably the simplest
> solution, but it's a kludgy work-around for what is, in my opinion, a
> kernel bug: if you are going to require people to specify an absolute
> disk drive index for the root partition, then you'd better index
> drives in a consistent order from one boot to the next.
>
> Switching to a GPT partition table sounds like the cleanest solution,
> but I need to figure out if the grub (legacy) ebuild includes GPT
> support or not.  I know it's supported by grub2, but I don't really
> feel like switching to grub2 ATM.
>
> --
> Grant Edwards               grant.b.edwards        Yow! But was he mature
>                                   at               enough last night at the
>                               gmail.com            lesbian masquerade?
>
>
>


-- 
Mit freundlichen Grüßen / Best regards

Randolph Maaßen

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Re: [gentoo-user] Re: Can't find init due to inconsistent drive order

[Wang Xuerui]

2013/7/2 Grant Edwards <grant.b.edwards@gmail.com>:
> It looks like my options are:
>
> <snip>
>
>  5) For the drive with the root parition on it switch from a DOS
>     parition table to a GPT partition table and use the
>     root=PARTUUID=<whatever> kernel option.
>
> Switching to a GPT partition table sounds like the cleanest solution,
> but I need to figure out if the grub (legacy) ebuild includes GPT
> support or not.  I know it's supported by grub2, but I don't really
> feel like switching to grub2 ATM.

I'm not exactly sure about your system's setup, but msdos partition
tables can also hold partition UUIDs, which can be seen by running
blkid. So, such a solution does not necessarily imply a GPT-based
setup... you can experiment with it a bit, having fun tweaking kernel
parameters :)

[gentoo-user] Re: Can't find init due to inconsistent drive order

[Grant Edwards]

On 2013-07-02, Randolph Maa?en <r.maassen60@gmail.com> wrote:
> 2013/7/2 Grant Edwards <grant.b.edwards@gmail.com>

>> It looks like my options are:
>>
[...]
>>
>>  5) For the drive with the root parition on it switch from a DOS
>>     parition table to a GPT partition table and use the
>>     root=PARTUUID=<whatever> kernel option.
>
> You don't need to switch to GPT for that. I have a DOS partitioned disk and
> "blkid" prints the LABEL and UUID for each partition.

And you can pass those values to the kernel via  the "root=" parameter?

-- 
Grant Edwards               grant.b.edwards        Yow! NEWARK has been
                                  at               REZONED!!  DES MOINES has
                              gmail.com            been REZONED!!

Re: [gentoo-user] Re: Can't find init due to inconsistent drive order

[Daniel Frey]

On 07/02/2013 07:23 AM, Grant Edwards wrote:
> On 2013-07-01, Grant Edwards <grant.b.edwards@gmail.com> wrote:
> 
> 
>  2) Unplug or power down the firewire drive when booting. 
> 

I had this problem on my Intel motherboard, and found out you can
disable booting from external drives. "Boot to removable devices" or
similar in the BIOS. Failing that, changing the boot order so that the
firewire/USB device is at the very end of the boot list may help your
situation.

> 
> Number 6 (fixing the kernel) is The Right Thing To Do(tm), but it's a
> bit out of scope for the momement.  The "early code" in the kernel
> obviously knows how to read partition tables and also knows about the
> relevent file system, so I'm a bit baffled why it can't look at the
> file system label.
>     

Is CONFIG_EDD set?

CONFIG_EDD:


                                                  Say Y or M here if you
want to enable BIOS Enhanced Disk Drive Services real mode BIOS calls to
determine which disk
BIOS tries boot from.  This information is then exported via sysfs.


Dan

Re: [gentoo-user] Re: Can't find init due to inconsistent drive order

[Randolph Maaßen]

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2013/7/2 Grant Edwards <grant.b.edwards@gmail.com>

> On 2013-07-02, Randolph Maa?en <r.maassen60@gmail.com> wrote:
> > 2013/7/2 Grant Edwards <grant.b.edwards@gmail.com>
>
> >> It looks like my options are:
> >>
> [...]
> >>
> >>  5) For the drive with the root parition on it switch from a DOS
> >>     parition table to a GPT partition table and use the
> >>     root=PARTUUID=<whatever> kernel option.
> >
> > You don't need to switch to GPT for that. I have a DOS partitioned disk
> and
> > "blkid" prints the LABEL and UUID for each partition.
>
> And you can pass those values to the kernel via  the "root=" parameter?
>
>
Yep.
The G in GPT just means that the type of the partition is stored as
GUID/UUID. The partition ID is a separate value.


> --
> Grant Edwards               grant.b.edwards        Yow! NEWARK has been
>                                   at               REZONED!!  DES MOINES
> has
>                               gmail.com            been REZONED!!
>
>
>


-- 
Mit freundlichen Grüßen / Best regards

Randolph Maaßen

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Re: [gentoo-user] Re: Can't find init due to inconsistent drive order

[Bruce Hill]

On Tue, Jul 02, 2013 at 02:42:15PM +0000, Grant Edwards wrote:
> >
> > You don't need to switch to GPT for that. I have a DOS partitioned disk and
> > "blkid" prints the LABEL and UUID for each partition.
> 
> And you can pass those values to the kernel via  the "root=" parameter?

That still requires an initrd/initramfs, iirc.
-- 
Happy Penguin Computers               >')
126 Fenco Drive                       ( \
Tupelo, MS 38801                       ^^
support@happypenguincomputers.com
662-269-2706 662-205-6424
http://happypenguincomputers.com/

A: Because it messes up the order in which people normally read text.                                                                                                                                                          
Q: Why is top-posting such a bad thing?                                                                                                                                                                                        
A: Top-posting.                                                                                                                                                                                                                
Q: What is the most annoying thing in e-mail?

Don't top-post: http://en.wikipedia.org/wiki/Top_post#Top-posting

[gentoo-user] Re: Can't find init due to inconsistent drive order

[Grant Edwards]

On 2013-07-02, Daniel Frey <djqfrey@gmail.com> wrote:
> On 07/02/2013 07:23 AM, Grant Edwards wrote:
>> On 2013-07-01, Grant Edwards <grant.b.edwards@gmail.com> wrote:
>> 
>> 
>>  2) Unplug or power down the firewire drive when booting. 
>> 
>
> I had this problem on my Intel motherboard, and found out you can
> disable booting from external drives. "Boot to removable devices" or
> similar in the BIOS. Failing that, changing the boot order so that the
> firewire/USB device is at the very end of the boot list may help your
> situation.

The problem isn't that the BIOS is booting the wrong drive.  The BIOS
is booting the correct drive, grub is starting, grub is loading the
correct kernel.  When the _kernel_ runs it (sometimes) identifies disk
drives in the wrong order and tries to mount the root directory from
the wrong drive.

>> Number 6 (fixing the kernel) is The Right Thing To Do(tm), but it's a
>> bit out of scope for the momement.  The "early code" in the kernel
>> obviously knows how to read partition tables and also knows about the
>> relevent file system, so I'm a bit baffled why it can't look at the
>> file system label.
>>     
>
> Is CONFIG_EDD set?
>
> CONFIG_EDD:
>
> Say Y or M here if you want to enable BIOS Enhanced Disk Drive
> Services real mode BIOS calls to determine which disk BIOS tries boot
> from.  This information is then exported via sysfs.

This has nothing to do with what disk drive the BIOS tries to boot
from (there's no problem with that).

-- 
Grant Edwards               grant.b.edwards        Yow! I'm wearing PAMPERS!!
                                  at               
                              gmail.com            

[gentoo-user] Re: Can't find init due to inconsistent drive order

[Grant Edwards]

On 2013-07-02, Bruce Hill <daddy@happypenguincomputers.com> wrote:
> On Tue, Jul 02, 2013 at 02:42:15PM +0000, Grant Edwards wrote:
>>
>>> You don't need to switch to GPT for that. I have a DOS partitioned disk and
>>> "blkid" prints the LABEL and UUID for each partition.
>> 
>> And you can pass those values to the kernel via  the "root=" parameter?
>
> That still requires an initrd/initramfs, iirc.

The PARTUUID= parition specifier format is handled directly by kernel
code, so I don't see why it should require an initrd (unless the UUID
values for MBR partitions aren't actually something the kernel knows
about and are something made up from whole cloth by the blkid program)

-- 
Grant Edwards               grant.b.edwards        Yow! ... I have read the
                                  at               INSTRUCTIONS ...
                              gmail.com            

Re: [gentoo-user] Re: Can't find init due to inconsistent drive order

[Neil Bothwick]

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On Tue, 2 Jul 2013 15:09:28 +0000 (UTC), Grant Edwards wrote:

> > I had this problem on my Intel motherboard, and found out you can
> > disable booting from external drives. "Boot to removable devices" or
> > similar in the BIOS. Failing that, changing the boot order so that the
> > firewire/USB device is at the very end of the boot list may help your
> > situation.  
> 
> The problem isn't that the BIOS is booting the wrong drive.  The BIOS
> is booting the correct drive, grub is starting, grub is loading the
> correct kernel.  When the _kernel_ runs it (sometimes) identifies disk
> drives in the wrong order and tries to mount the root directory from
> the wrong drive.

And the BIOS order can affect the order in which the kernel sees the
drives, so it is worth trying.

I'd go for the firewire-as-a-module approach and add the module
to /etc/conf.d/modules to make sure it is loaded ASAP. Yes, it is a
kludge, but it is the simplest solution from a practical POV.


-- 
Neil Bothwick

Processor: (n.) a device for converting sense to nonsense at the speed
           of electricity, or (rarely) the reverse.

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Re: [gentoo-user] Re: Can't find init due to inconsistent drive order

[Neil Bothwick]

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On Tue, 2 Jul 2013 15:16:15 +0000 (UTC), Grant Edwards wrote:

> The PARTUUID= parition specifier format is handled directly by kernel
> code, so I don't see why it should require an initrd (unless the UUID
> values for MBR partitions aren't actually something the kernel knows
> about and are something made up from whole cloth by the blkid program)

MBRs don't have PARTUUIDs do they? Don't confuse them with filesystem
UUIDs as used in fstab.


-- 
Neil Bothwick

Oops. My brain just hit a bad sector.

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[gentoo-user] Re: Can't find init due to inconsistent drive order

[Grant Edwards]

On 2013-07-02, Randolph Maa?en <r.maassen60@gmail.com> wrote:
> 2013/7/2 Grant Edwards <grant.b.edwards@gmail.com>

>> I still haven't figured out why my drives suddenly started getting
>> discovered in varying orders. [...]
>>
>> It looks like my options are:

[...]
>
>>  5) For the drive with the root parition on it switch from a DOS
>>     parition table to a GPT partition table and use the
>>     root=PARTUUID=<whatever> kernel option.
>
> You don't need to switch to GPT for that.


All the references Google can find for me say that you have to use a
GPT partition table if you want to specify a boot partition using
root=PARTUUID=<partition-uuid>.

Does the root=PARTUUID option work for you?

Can you point to some documentation on how you can use
root=PARTUID=<partition-uuid> with an DOS/MBR partition table?

> I have a DOS partitioned disk and "blkid" prints the LABEL and UUID
> for each partition.

Anybody can write a program to gnerate and print a UUID for a
partition.  What matters is what the _kernel_ thinks the partition
UUID is.

I added some printk() calls to the kernel mount code to print out the
parition UUIDs.  They don't match the UUIDs printed by blkid:

                      kernel           blkid
           sector      UUID             UUID

sda1          64  0004c99d-01    66E1C3CF7C012A2E
sda2   209715264  0004c99d-02    e9a3eb9e-10d0-4075-aacf-018219cf77a3
sda3   211812416  <null>         n/a
sda4   <n/a>      <n/a>          n/a
sda5   211812480  0004c99d-05    ab4724ab-9030-4217-8582-00f0abe1a48e
sda6   421527744  0004c99d-06    n/a
sda7   429916416  0004c99d-07    13c0fbde-db8a-4784-861a-b3f4e4cdd8f5
sda8   639631680  0004c99d-08    d0f87d87-002c-4d12-b5f3-193d9b0bebee
sda9   849346944  0004c99d-09    03c479f0-ecf8-4060-885b-b350368deee8
sda10 1059062208  0004c99d-0a    60acb3d3-ce8e-48ce-b197-858bc51a74ea
sda11 1268777472  0004c99d-0b    n/a
sda12 1478492736  0004c99d-0c    n/a
sda13 1688208000  0004c99d-0d    n/a
sda14 1897923264  0004c99d-0e    n/a

IOW, it appears that the "blkid" program is either just making stuff
up or its the filesystem UUID rather than the partition UUID. I
suspect the latter, since I notice that blkid doesn't print a UUID for
paritions that don't have filesystems.

One might think that one could use root=PARTUUID=0004c99d-06 instead
of root=/dev/sda5, but the kernel will reject any partition UUID
strings shorter than 36 characters.

-- 
Grant Edwards               grant.b.edwards        Yow! ... I see TOILET
                                  at               SEATS ...
                              gmail.com            

Re: [gentoo-user] Re: Can't find init due to inconsistent drive order

[Neil Bothwick]

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On Tue, 2 Jul 2013 16:57:26 +0000 (UTC), Grant Edwards wrote:

> IOW, it appears that the "blkid" program is either just making stuff
> up or its the filesystem UUID rather than the partition UUID. I
> suspect the latter, since I notice that blkid doesn't print a UUID for
> paritions that don't have filesystems.

UUIDs are for filesystems, PARTUUIDs ae for partitions - blkid prints
both, but only if both are present, which requires a GPT partition table.


-- 
Neil Bothwick

A man needs a mistress - just to break the monogamy

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[gentoo-user] Re: Can't find init due to inconsistent drive order

[Grant Edwards]

On 2013-07-02, Neil Bothwick <neil@digimed.co.uk> wrote:
> On Tue, 2 Jul 2013 16:57:26 +0000 (UTC), Grant Edwards wrote:
>
>> IOW, it appears that the "blkid" program is either just making stuff
>> up or its the filesystem UUID rather than the partition UUID. I
>> suspect the latter, since I notice that blkid doesn't print a UUID for
>> paritions that don't have filesystems.
>
> UUIDs are for filesystems, PARTUUIDs ae for partitions - blkid prints
> both, but only if both are present, which requires a GPT partition table.

I found some references to blkid at one time generating PARTUUID
values for MBR partitions, but that feature got removed.

-- 
Grant Edwards               grant.b.edwards        Yow! How's the wife?
                                  at               Is she at home enjoying
                              gmail.com            capitalism?

Re: [gentoo-user] Re: Can't find init due to inconsistent drive order

[Paul Hartman]

On Tue, Jul 2, 2013 at 11:57 AM, Grant Edwards
<grant.b.edwards@gmail.com> wrote:
>
>
> All the references Google can find for me say that you have to use a
> GPT partition table if you want to specify a boot partition using
> root=PARTUUID=<partition-uuid>.
>
> Does the root=PARTUUID option work for you?
>
> Can you point to some documentation on how you can use
> root=PARTUID=<partition-uuid> with an DOS/MBR partition table?

As Neil alluded to, you can use UUID with MBR (instead of PARTUUID and
GPT). I have DOS/MBR partition table and my kernel commandline looks
like:

root=UUID=1d21fa55-0fa9-4d43-8d41-8b4193900efa ro log_buf_len=1M quiet
rootfstype=ext4 raid=noautodetect

(along with an initramfs)

[gentoo-user] Re: Can't find init due to inconsistent drive order

[Grant Edwards]

On 2013-07-02, Paul Hartman <paul.hartman+gentoo@gmail.com> wrote:
> On Tue, Jul 2, 2013 at 11:57 AM, Grant Edwards
><grant.b.edwards@gmail.com> wrote:

>>>>  5) For the drive with the root parition on it switch from a DOS
>>>>     parition table to a GPT partition table and use the
>>>>     root=PARTUUID=<whatever> kernel option.
>>>
>>> You don't need to switch to GPT for that.
>>
>> All the references Google can find for me say that you have to use a
>> GPT partition table if you want to specify a boot partition using
>> root=PARTUUID=<partition-uuid>.
>>
>> Does the root=PARTUUID option work for you?
>>
>> Can you point to some documentation on how you can use
>> root=PARTUID=<partition-uuid> with an DOS/MBR partition table?
>
> As Neil alluded to, you can use UUID with MBR (instead of PARTUUID and
> GPT). I have DOS/MBR partition table and my kernel commandline looks
> like:
>
> root=UUID=1d21fa55-0fa9-4d43-8d41-8b4193900efa ro log_buf_len=1M quiet
> rootfstype=ext4 raid=noautodetect
>
> (along with an initramfs)

Yes, we've already discussed that if you have an initrd (or
initramfs), and an 'init' program that handles it, you can use
filesystem labels and filesystem uuids.

The option we were discussing in the posting to which you replied is
that of using the root=PARTUUID method which is handled directly by
the kernel.  I said that requires switching from MBR to GPT, and was
told "You don't need to switch to GPT for that." The evidence for that
last statement seemed to be the fact the 'blkid' command prints out
filesystem UUIDs.

I tried using root=PARTUUID= with an MBR and the UUID values printed
by 'blkid': it didn't work.  I even modified the kernel to show the
kernel's partition UUIDs that were being compared against.

I still maintain that you _do_ need to switch to GPT to use
root=PARTUUID but would welcome any evidence or documentation that
indicates otherwise.

-- 
Grant Edwards               grant.b.edwards        Yow! The Korean War must
                                  at               have been fun.
                              gmail.com            

[gentoo-user] Re: Can't find init due to inconsistent drive order

[Grant Edwards]

On 2013-07-02, Randolph Maa?en <r.maassen60@gmail.com> wrote:
> 2013/7/2 Grant Edwards <grant.b.edwards@gmail.com>
>
>> On 2013-07-02, Randolph Maa?en <r.maassen60@gmail.com> wrote:
>>> 2013/7/2 Grant Edwards <grant.b.edwards@gmail.com>
>>
>>>> It looks like my options are:
>>>>
>> [...]
>>>>
>>>>  5) For the drive with the root parition on it switch from a DOS
>>>>     parition table to a GPT partition table and use the
>>>>     root=PARTUUID=<whatever> kernel option.
>>>
>>> You don't need to switch to GPT for that. I have a DOS partitioned
>>> disk and "blkid" prints the LABEL and UUID for each partition.
>>
>> And you can pass those values to the kernel via  the "root=" parameter?
>
> Yep. The G in GPT just means that the type of the partition is stored
> as GUID/UUID. The partition ID is a separate value.

I think you're confusing the partition UUID and the filesystem UUID
(which I believe is what's printed by blkid).

GPT provides a partition UUID you can use to tell the kernel where
root is.  DOS/MBR does not.

-- 
Grant Edwards               grant.b.edwards        Yow! I just had my entire
                                  at               INTESTINAL TRACT coated
                              gmail.com            with TEFLON!

[gentoo-user] Re: Can't find init due to inconsistent drive order

[Grant Edwards]

On 2013-07-02, Neil Bothwick <neil@digimed.co.uk> wrote:
> On Tue, 2 Jul 2013 15:16:15 +0000 (UTC), Grant Edwards wrote:
>
>> The PARTUUID= parition specifier format is handled directly by kernel
>> code, so I don't see why it should require an initrd (unless the UUID
>> values for MBR partitions aren't actually something the kernel knows
>> about and are something made up from whole cloth by the blkid program)
>
> MBRs don't have PARTUUIDs do they? Don't confuse them with filesystem
> UUIDs as used in fstab.

No, blkid does not print a "PARTUUID" value with an MBR. In only prints
"UUID" values, which as you noted, are _filesystem_ UUIDs.  If you
want to use a filesystem UUID to locate the root partition, you need
an initramfs/initrd which contains an 'init' program that finds the
filesystem with the specified UUID, mounts that filesystem, and then
does a root_pivot.

-- 
Grant Edwards               grant.b.edwards        Yow! Hello.  Just walk
                                  at               along and try NOT to think
                              gmail.com            about your INTESTINES being
                                                   almost FORTY YARDS LONG!!

[gentoo-user] Re: Can't find init due to inconsistent drive order

[Grant Edwards]

On 2013-07-02, Neil Bothwick <neil@digimed.co.uk> wrote:
> On Tue, 2 Jul 2013 15:09:28 +0000 (UTC), Grant Edwards wrote:
>
>> > I had this problem on my Intel motherboard, and found out you can
>> > disable booting from external drives. "Boot to removable devices" or
>> > similar in the BIOS. Failing that, changing the boot order so that the
>> > firewire/USB device is at the very end of the boot list may help your
>> > situation.  

[...]

> I'd go for the firewire-as-a-module approach and add the module to
> /etc/conf.d/modules to make sure it is loaded ASAP. Yes, it is a
> kludge, but it is the simplest solution from a practical POV.

I changed the firewire storage driver from in-kernel to module, and
that looks like it solves the problem.  It appears to get
demand-loaded immediately after root is mounted.

Next time I do an install, I think I'll try GPT...

-- 
Grant Edwards               grant.b.edwards        Yow! Now, let's SEND OUT
                                  at               for QUICHE!!
                              gmail.com            

Re: [gentoo-user] Re: Can't find init due to inconsistent drive order

[Randolph Maaßen]

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2013/7/2 Grant Edwards <grant.b.edwards@gmail.com>

> On 2013-07-02, Neil Bothwick <neil@digimed.co.uk> wrote:
> > On Tue, 2 Jul 2013 15:16:15 +0000 (UTC), Grant Edwards wrote:
> >
> >> The PARTUUID= parition specifier format is handled directly by kernel
> >> code, so I don't see why it should require an initrd (unless the UUID
> >> values for MBR partitions aren't actually something the kernel knows
> >> about and are something made up from whole cloth by the blkid program)
> >
> > MBRs don't have PARTUUIDs do they? Don't confuse them with filesystem
> > UUIDs as used in fstab.
>
> No, blkid does not print a "PARTUUID" value with an MBR. In only prints
> "UUID" values, which as you noted, are _filesystem_ UUIDs.  If you
> want to use a filesystem UUID to locate the root partition, you need
> an initramfs/initrd which contains an 'init' program that finds the
> filesystem with the specified UUID, mounts that filesystem, and then
> does a root_pivot.
>
> --
> Grant Edwards               grant.b.edwards        Yow! Hello.  Just walk
>                                   at               along and try NOT to
> think
>                               gmail.com            about your INTESTINES
> being
>                                                    almost FORTY YARDS
> LONG!!
>
>
>
SCREW ME! Still messing around with these IDs.

Sorry for disturbance.

-- 
Mit freundlichen Grüßen / Best regards

Randolph Maaßen

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Re: [gentoo-user] Re: Can't find init due to inconsistent drive order

[Paul Hartman]

On Tue, Jul 2, 2013 at 3:27 PM, Grant Edwards <grant.b.edwards@gmail.com> wrote:
>>> Can you point to some documentation on how you can use
>>> root=PARTUID=<partition-uuid> with an DOS/MBR partition table?
>>
>> As Neil alluded to, you can use UUID with MBR (instead of PARTUUID and
>> GPT). I have DOS/MBR partition table and my kernel commandline looks
>> like:
>>
>> root=UUID=1d21fa55-0fa9-4d43-8d41-8b4193900efa ro log_buf_len=1M quiet
>> rootfstype=ext4 raid=noautodetect
>>
>> (along with an initramfs)
>
> Yes, we've already discussed that if you have an initrd (or
> initramfs), and an 'init' program that handles it, you can use
> filesystem labels and filesystem uuids.
>
> The option we were discussing in the posting to which you replied is
> that of using the root=PARTUUID method which is handled directly by
> the kernel.

Ah, sorry, I missed that detail. I thought I was helping to clear up
confusion, when in fact I was the confused one! :)

Re: [gentoo-user] Re: Can't find init due to inconsistent drive order

[Neil Bothwick]

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On Tue, 2 Jul 2013 20:40:20 +0000 (UTC), Grant Edwards wrote:

> Next time I do an install, I think I'll try GPT...

I can't think why any sane person would do otherwise. Who in their right
mind would want to use a 30+year old format where any more than four
partitions is a fragile kludge? :-O


-- 
Neil Bothwick

Eat shit - 50 million flies can't be wrong
Use Microsoft . . . . .

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