Re: Can't Mount CF-Card on boot of 2.6.15 Kernel on EPIA - VFS: Cannot open root device

["Randy.Dunlap" <rdunlap@xenotime.net>]

On Tue, 13 Jun 2006 23:10:04 +0200 Markus Biermaier wrote:

> 
> Am 12.06.2006 um 21:09 schrieb Jan Engelhardt:
> 
> 
> > Hm. Maybe http://lkml.org/lkml/2005/2/26/92 (updated version for
> > 2.6.16/.17 below) can help you.
> >
> > diff --fast -Ndpru linux-2.6.17-rc6~/block/genhd.c linux-2.6.17-rc6 
> > +/block/genhd.c
> > --- linux-2.6.17-rc6~/block/genhd.c	2006-06-06 02:57:02.000000000  
> > +0200
> > +++ linux-2.6.17-rc6+/block/genhd.c	2006-06-08 22:29:16.607058000  
> > +0200
> > @@ -214,6 +214,52 @@ struct gendisk *get_gendisk(dev_t dev, i
> >  	return  kobj ? to_disk(kobj) : NULL;
> >  }
> >
> > +/*
> > + * printk a full list of all partitions - intended for
> > + * places where the root filesystem can't be mounted and thus
> > + * to give the victim some idea of what went wrong
> > + */
> > +void printk_all_partitions(void)
> >
> 
> 
> Am 13.06.2006 um 09:47 schrieb Markus Biermaier:
> 
> 
> > to get the function "printk_all_partitions" compiled I simply  
> > commented out "mutex_lock" and "mutex_unlock"...
> >
> > So the result before the boot-panic is:
> >
> > ...
> > here are the partitions available:
> > 2100     500472 hde driver: ide-disk
> >   2101     500440 hde1
> > ...
> > What does this mean?
> >
> 
> This holds the solution:
>                          /* Note, unlike /proc/partitions I'm showing  
> the numbers in hex
>                             in the same format as the root= option */
>                          printk("%02x%02x %10llu %s",
>                                 sgp->major, sgp->first_minor,
>                                 (unsigned long long)get_capacity(sgp)  
>  >> 1,
>                                 disk_name(sgp, 0, buf));
> 
> So my "/tftpboot/pxelinux.cfg/Cxxxxxx" is:
> ------------------------- [ BEGIN Cxxxxxx ] -------------------------
> DEFAULT standard
> LABEL standard
> KERNEL vmlinuz
> # APPEND initrd=initrd ramdisk_size=32768 root=/dev/hde1 udev  
> acpi=off rootdelay=5
> APPEND initrd=initrd ramdisk_size=32768 root=2101 udev acpi=off  
> rootdelay=5
> ------------------------- [ END   Cxxxxxx ] -------------------------
> 
> so the right root-string is: "root=2101".
> 
> But can anyone tell me how "root=/dev/hde1" translates to "root=2101"???

That's (hex) 0x2101.  In Documentation /devices.txt, we see:

 33 block	Third IDE hard disk/CD-ROM interface
		  0 = /dev/hde		Master: whole disk (or CD-ROM)
		 64 = /dev/hdf		Slave: whole disk (or CD-ROM)

		Partitions are handled the same way as for the first
		interface (see major number 3)

So device 33 (hex 21) is /dev/hde and 0x01 is partition 1 == hde1.


> Thank you very much, Jan.
> 
> You brought me the solution.


---
~Randy