[LUG] Device numbers

[Grant Sewell <dcglug@xxxxxxxxxxxx>]

On Fri, 15 Feb 2008 21:32:10 +0000
james kilty wrote:

> It seems to be updated 2 or 3 times a week, with one thing or another.
> Superb process. It's always interesting to turn on the terminal to see
> exactly what is happening. 
> 
> BTW I get an error message at times in the terminal display saying
> device number 169 is not configured. How do I determine what such a
> device might be and configure it when I next get the message?
> 
> Thanks.

Under Linux devices are files.  Differentiating them with different
file names makes sense for the use (ie /dev/cdrom1 vs /dev/ttyUSB0),
but these names do not necessarily mean anything useful to the kernel.
As such, all devices are differentiated by major and minor numbers.
For example, SCSI CD drives (or those that are using SCSI emulation)
have a major number of 11 and the minor number determines which device
it is (0, 1, 2, etc).

With kernel sources install (as opposed to just the kernel headers) you
get a lot of text files under [kernel source location]/Documentation.
One of these, devices.txt, lists the device major and minor numbers.
 Interestingly devices with a major number of 169 seem to be:

169 char        Eracom CSA8000 PCI encryption adaptor
                  0 = /dev/ecsa8-0      First CSA8000
                  1 = /dev/ecsa8-1      Second CSA8000
                    ...

Under Ubuntu there are *lots* of /dev/pty* and /dev/tty* devices.
Here's what devices.txt has to say about them:
  2 char        Pseudo-TTY masters
                  0 = /dev/ptyp0        First PTY master
                  1 = /dev/ptyp1        Second PTY master
                    ...
                255 = /dev/ptyef        256th PTY master

                Pseudo-tty's are named as follows:
                * Masters are "pty", slaves are "tty";

  3 char        Pseudo-TTY slaves
                  0 = /dev/ttyp0        First PTY slave
                  1 = /dev/ttyp1        Second PTY slave
                    ...
                255 = /dev/ttyef        256th PTY slave

                These are the old-style (BSD) PTY devices; Unix98
                devices are on major 136 and above.

  4 char        TTY devices
                  0 = /dev/tty0         Current virtual console

                  1 = /dev/tty1         First virtual console
                    ...
                 63 = /dev/tty63        63rd virtual console
                 64 = /dev/ttyS0        First UART serial port
                    ...
                255 = /dev/ttyS191      192nd UART serial port

As we can see, each on of these can have a minor number of 169.

Without more specific error messages to see, it's hard to diagnose.

Incidentally, if you use the command line (apt-get update / apt-get
upgrade) you can copy/paste the error much more easily. :)

Grant.

-- 
The Mailing List for the Devon & Cornwall LUG
http://mailman.dclug.org.uk/listinfo/list
FAQ: http://www.dcglug.org.uk/linux_adm/list-faq.html