problem with dropbear, pty??, and busybox

Hans-Jürgen Koch hjk at linutronix.de
Fri Jun 22 18:02:24 WST 2007


Am Freitag 22 Juni 2007 08:08 schrieb Matt Johnston:
> On Thu, Jun 21, 2007 at 09:41:07PM +0200, Hans-Jürgen Koch wrote:
> > I'm trying to use dropbear-0.49 on an ARM board (PXA270) running 
> > Linux 2.6.21.5.
> > I'm using busybox-1.6.0 (don't know if that's related).
> > 
> > The dropbear daemon starts without complaining. If I try to login with ssh
> > from an other computer, authentication (password) works, but then dropbear 
> > hangs and spits out this error:
> > 
> > failed to open any /dev/pty?? devices
> > no pty was allocated, couldn't execute
> > 
> > It's true, I don't have any /dev/pty devices. I used
> > 
> > ./configure --disable-syslog --disable-openpty --disable-utmp --disable-utmpx
> > to avoid them.
> 
> You need some sort of PTY support to run any sort of
> virtual terminal (ie, a normal SSH login). I have got no
> idea what sort of Linux distro you're using, but often
> they'll take care of it for you.

It's not a real distro, I compiled a minimal root file system
using busybox plus the files that come with the scratchbox
ARM toolchain. I haven't installed udev yet, that's why I
only have the /dev files I created myself.

> 
> You will have to create the appropriate PTY devices in /dev
> for it to work. If you make sure /dev/ptmx and /dev/tty
> devices exist (use mknod or the makedev script that come
> with your distro (or buildroot??)) and then mount devpts at
> /dev/pts, you should be able to use normal openpty()
> support. You'll want to get rid of the --disable-openpty
> configure argument.

I created /dev/ptmx manually (I already had /dev/tty), added 
devpts to my fstab, and compiled dropbear without --disable-openpty.
That made it work, thanks for that hint!

> 
> Alternatively you can manually create 
>  /dev/[pt]ty[pqrstuwxyzPQRST][0123456789abcdef]
> nodes as appropriate and keep the --disable-openpty
> configure argument. That will try opening each of
> those devices sequentially until one succeeds.

Didn't try that one.

Thanks a lot for your help!

Cheers,
Hans



More information about the Dropbear mailing list