[ILUG] Help, Please! User Mode Linux on Debian - ethertap problem

[Cormac McClean]

Hi David,

Thanks for your reply. I switched to Libranet which has the a 2.4.19 kernel, 
with built-in tun/tap support. I'm wondering if I need to recompile the UML 
kernel to include tun/tap, as I get the following error messages when I try 
to ifconfig eth0 on the UML:
tuntap_open_tramp : didn't receive a message
* insmod tun
insmod: tun: no module by that name found
Opening /dev/net/tun failed : No such device
tuntap_open_tramp failed - errno = 22
tuntap_open_tramp : didn't receive a message
* insmod tun
insmod: tun: no module by that name found
Opening /dev/net/tun failed : No such device
tuntap_open_tramp failed - errno = 22

I've had another look at the http://uml.openconsultancy.com link and I think 
I'll follow the instructions for building the UML kernel.

Thanks,
Cormac.

Hi Cormac

I'd suggest using the TUN/TAP device rather than ETHERTAP. You should
upgrade the kernel from the default Woody one, but you probably don't
need to compile a new one yourself. (disclaimer: I'm not all that
familiar with TUN/TAP support in current Debian kernels).

If you need to create ETHERTAP or TUN/TAP devices you can do it yourself
with mknod. For example, for the TUN/TAP device you need to do:

        mknod /dev/net/tun c 10 200

And then set appropriate permissions so that the user running the UML
can use it.

I've found the descriptions on http://uml.openconsultancy.com/ very
helpful in the past, and http://user-mode-linux.sf.net/networking.html
is also a useful resource.

You might also find the init/control scripts I've written helpful:
http://cagraidsvr06.cs.tcd.ie/distribution/umlinux/uml-host/
They're a bit specific to our setup in places (RedHat 7.3, using LCFG
(http://www.lcfg.org/) as an install system) but should be hackable to
meet your needs. There's some (incomplete and out-of-date) documentation 
here: http://www.cs.tcd.ie/David.OCallaghan/grid/uml-lcfgng.pdf

David

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