Vijay Tandeker wrote:
> Hi All,
> I am Vijay, working as software engineer in Tejas Networks Bangalore,
> India.
>
> I downloaded the following:
> - UML Kernel image v3.18 for i386 32 bit
> - root filesystem for Ubuntu-14 and Fedora21
>
> My system configuration:
> - Ubuntu-14.04 32 bit
> - Kernel : 3.19
>
> After downloading ran the following command:
> ./kernel ubda=Ubuntu_root_fs
>
> After sometime, Got the following error continuously:
> - getmaster : no usable host pty device
>
> I am unable to get the console.
>
> I searched in internet about the solution but no luck. Tried with Fedora
> root_fs also but no success.
>
> Please help.
>
> Regards,
>
>
> Vijay
Its hard to tell from your description if you are getting the message
from inside the UML or outside. I'm basically guessing it must be from
outside, stuff the kernel is dropping on the screen.
I use and have launched Debian instances, and few other distros, in UML
instances. Since Ubuntu is descended from Debian my experience may
apply. The number one cause for problems that I've had and could give
messages similar to yours has been with the Linux distro inside the UML
trying to open virtual consoles. To cut down on a number of related
issues I usually do something like this:
$ ./kernel con0=null,fd:2 con1=fd:0,fd:1 con=null ssl=null
ubda=Ubuntu_root_fs
This is what the new switches do:
* "con0=null,fd:2": ties "console 0" to stderr, without any input.
Debian, and probably Ubuntu, use this for boot messages.
* "con1=fd:0,fd:1": ties the stdin and stdout of the current terminal
session into "console 1", which is usually the first login console.
* "con=null": Turns off all other consoles, so if the distro in the
UML tries to access any others it will get an error, simply failing
to launch additional consoles, which shouldn't affect usability.
* "ssl=null": Turns off all serial ports. This for the same reason as
above.
If you don't use the assorted con and ssl flags to specify which virtual
devices to attach to real devices and which ones to turn off, the Linux
image, inside the UML, will more than likely try to open a dozen or so
consoles and possibly serial ports. That is unless its been customized
specifically for UML use. The default action within the UML kernel
("./kernel") is typically to launch xterms for virtual console and
serial port, which gets to be real messy or to open "ptys" (pseudo
terminals), directly. Xterms need PTYs too... so its the same problem.
I don't know much about the Linux PTY system because in my experience it
just works. Ubuntu does things a bit differently so there might be a
package, or more than likely, a permission problem with your user account.
There is much more to say on this but the revised command above may give
you some instant gratification or at least help to diagnose the problem.
Its also good to read the page documenting those UML CLI (con*, ssl*)
switches: http://user-mode-linux.sourceforge.net/old/input.html.
- Jon
--
Sent from my Debian Linux workstation -- http://www.debian.org/intro/about
Jon Foster
JF Possibilities, Inc.
j...@jfpossibilities.com
541-410-2760
Making computers work for you!
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