bootcd: dd: /dev/ram: Device not configured

Richard Lightman richard at reika.demon.co.uk
Fri Jul 6 01:51:37 PDT 2001


Misquoted from DrJekyll on 2001/07/ 6 at 10:00 +0000:
> Hi
> 
> I am trying to build my own bootcd following the lfshint by nicholas dille.
> But there occurs a problem when I am trying to create the ramdisk: dd:
> /dev/ram: Device not configured
> I compiled the support for the ramdisk and the initial ramdisk statically in
> the kernel and the devices /dev/ram, /dev/ram1, ... are available in my
> /dev-directory.
> So what is the problem??? Can anybody help me out???
> 
There are two types of ramdisk. When configuring the kernel:

Block devices  --->
  < > RAM disk support

or
  <M> RAM disk support
  (4096)    Default RAM disk size (NEW)

or
  <*> RAM disk support
  (4096)    Default RAM disk size (NEW)
  [ ]   Initial RAM disk (initrd) support



These have different device node minors.
>From /usr/src/linux/Documentation/devices.txt:

  0             Unnamed devices (e.g. non-device mounts)
...
    block       RAM disk
                  0 = /dev/ram0         First RAM disk
                  1 = /dev/ram1         Second RAM disk
                    ...
                250 = /dev/initrd       Initial RAM disk {2.6}


Take a look at:
/usr/src/linux/Documentation/ramdisk.txt
/usr/src/linux/Documentation/initrd.txt

If your root partition is going to be the cd, then
you want to mount an ordinary ramdisk to get /tmp

If you want a cd that will be able to boot on anything
without making the kernel huge, you will need to
get grub/lilo to load an initrd, which the kernel
will mount as root so it can load the approiate
modules (eg scsi driver)


I have only had a quick look at the hint. There are
some things I do differently that may be of interest.


Make /etc/mtab a link to /proc/mounts. If you do
this on your normal system, you can get rid of some
of the fiddling that keeps /etc/mtab correct, but
you will have to create and destroy loop back devices
by hand instead of having mount do it.



File systems  --->
  < > Simple RAM-based file system support

If you use this instead of ext2, the ramdisk will
be the same size as the data on it, not the fixed
size with ext2. The ramdisk will initially be empty
so populate it with something like this in you
init scripts:

  devfsd /dev
  mount -t proc proc /proc
  losetup -e NONE /dev/loop/0 /compressed_usr
  mount -a
  bzip2 -cd /compressed_var | tar -xC /var

/etc/fstab:

/dev/cdroms/cdrom0     /        iso9660   defaults,ro 0 0
/dev/loop/0            /usr     cramfs    defaults,ro 0 0
/dev/rd/0              /var     ramfs     defaults    0 0
/dev/discs/disc0/part1 /mnt/lfs resiserfs noauto      0 0
/dev/floppy/0          /floppy  auto      noauto,user 0 0


Richard

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