Which device did I boot from?

Which device did I boot from?

[William Estrada]

Hi group,

  Is there a way to determine which device I have booted from?  For example,
say I booted from a USB device, can I tell which one?  I did not find
anything in /proc FS other than the cmdline options.

  Please respond directly to MrUmunhum@popdial.com as I am not subscribed
to this mailing list.

  Thanks for your time.
-- 
  William Estrada 
<HTTP://www.Mt-Umunhum-Wireless.net/resume/william_estrada.html>    --  
MrUmunhum at popdial dot com <mailto:MrUmunhum@popdial.com>  --   
408-997-0743
  Skype ID: MrUmunhum
  HTTP://Mt-Umunhum-Wireless.net

Re: Which device did I boot from?

[Rene Herman]

William Estrada wrote:

> Is there a way to determine which device I have booted from?  For
> example, say I booted from a USB device, can I tell which one?  I did
> not find anything in /proc FS other than the cmdline options.

If you choose the (experimental) CONFIG_EDD option in your kernel then, 
with cooperation of your BIOS, you'll have a /sys/firmware/edd with at 
least some info about the BIOS boot device. For me:

/sys/firmware/edd/
`-- int13_dev80
     |-- extensions
     |-- info_flags
     |-- legacy_max_cylinder
     |-- legacy_max_head
     |-- legacy_sectors_per_track
     |-- mbr_signature
     |-- raw_data
     |-- sectors
     `-- version

I do not appear to have enough information there to be able to translate 
back to the linux device but drivers/firmware/edd.c seems to imply there 
might be for others. As far as I'm aware, it's the best that's available 
at least.

Rene.

Re: Which device did I boot from?

[Matt Domsch]

On Fri, Apr 14, 2006 at 11:52:17PM +0200, Rene Herman wrote:
> William Estrada wrote:
> 
> >Is there a way to determine which device I have booted from?  For
> >example, say I booted from a USB device, can I tell which one?  I did
> >not find anything in /proc FS other than the cmdline options.
> 
> If you choose the (experimental) CONFIG_EDD option in your kernel then, 
> with cooperation of your BIOS, you'll have a /sys/firmware/edd with at 
> least some info about the BIOS boot device. For me:

I suppose I should un-mark this as experimental.  It's been in the
kernel for a couple years, and shipping enabled in RHEL4 for over a
year with no problems (a recent buggy BIOS workaround the one
exception).

-- 
Matt Domsch
Software Architect
Dell Linux Solutions linux.dell.com & www.dell.com/linux
Linux on Dell mailing lists @ http://lists.us.dell.com

Re: Which device did I boot from?

[Arjan van de Ven]

On Fri, 2006-04-14 at 14:13 -0700, William Estrada wrote:
> Hi group,
> 
>   Is there a way to determine which device I have booted from?  

that may be really hard; EDD can tell you what disk your bios will try,
but remember that you may have booted from USB (not covered by EDD) or
even ethernet (using PXE). The kernel doesn't know... since all it knows
is that the bootloader put it into memory somewhere

Re: Which device did I boot from?

[Andrey Borzenkov]

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> > Is there a way to determine which device I have booted from?  For
> > example, say I booted from a USB device, can I tell which one?  I did
> > not find anything in /proc FS other than the cmdline options.
>
> If you choose the (experimental) CONFIG_EDD option in your kernel then,
> with cooperation of your BIOS, you'll have a /sys/firmware/edd with at
> least some info about the BIOS boot device. For me:

I am sorry but it does not tell about boot device. It contains all hard disks 
enumerated via EDD interface. I do not see any information 
under /sys/firmware/edd that would have allowed to guess boot device.

- -andrey

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Re: Which device did I boot from?

[Rene Herman]

Andrey Borzenkov wrote:

>> If you choose the (experimental) CONFIG_EDD option in your kernel then,
>> with cooperation of your BIOS, you'll have a /sys/firmware/edd with at
>> least some info about the BIOS boot device. For me:
> 
> I am sorry but it does not tell about boot device. It contains all hard disks 
> enumerated via EDD interface. I do not see any information 
> under /sys/firmware/edd that would have allowed to guess boot device.

int13_dev80 is the bootdevice. Or that used to be the case with things 
such as booting from SCSI at least. Don't know about booting from, say, USB.

Rene.

Re: Which device did I boot from?

[Andrey Borzenkov]

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On Saturday 15 April 2006 13:43, Rene Herman wrote:
> Andrey Borzenkov wrote:
> >> If you choose the (experimental) CONFIG_EDD option in your kernel then,
> >> with cooperation of your BIOS, you'll have a /sys/firmware/edd with at
> >> least some info about the BIOS boot device. For me:
> >
> > I am sorry but it does not tell about boot device. It contains all hard
> > disks enumerated via EDD interface. I do not see any information
> > under /sys/firmware/edd that would have allowed to guess boot device.
>
> int13_dev80 is the bootdevice. Or that used to be the case with things
> such as booting from SCSI at least. Don't know about booting from, say,
> USB.
>

OK. In this case udev creates links based on MBR signature; it can be used to 
infer real device:

{pts/0}% LC_ALL=C ll /dev/disk/by-id
lrwxrwxrwx  1 root root  9 Apr 12 21:36 edd-int13_dev80 -> ../../hda
lrwxrwxrwx  1 root root 10 Apr 12 21:36 edd-int13_dev80-part1 -> ../../hda1
lrwxrwxrwx  1 root root 10 Apr 12 21:36 edd-int13_dev80-part2 -> ../../hda2

Not sure about USB either.

- -andrey
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