how to run dropbear on a system with a R/O /dev?

[Robert P. J. Day]

On Tue, 23 Dec 2008, Grahame Bowland wrote:

> 2008/12/23 Robert P. J. Day <rpjday at crashcourse.ca>:
> > On Mon, 22 Dec 2008, Robert P. J. Day wrote:
> >
> >>
> >>   i suspect i already know the answer to this, but is there any way to
> >> run dropbear on a system whose /dev directory is part of a larger
> >> romfs?
> >>
> >>   ssh to such a system worked fine during development when the root
> >> filesystem was NFS mounted and, therefore, writable.  but once that
> >> rootfs is flashed and is now mounted as a romfs, not surprisingly,
> >> dropbear can no longer accept incoming requests because (i'm
> >> guessing) while the appropriate /dev/ttyp[0-9] device files are there,
> >> dropbear has no ability to change their owner/perms, is that it?
> >> which generates the log error message:
> >>
> >>    pty_allocate: openpty: No child processes
> >>    no pty was allocated, couldn't execute
> >>
> >>   is there a way around this?  i would have guessed not, but i'm
> >> willing to be pleasantly surprised.
> >
> >  actually, a thought just occurred to me.  i checked and, with an NFS
> > mount with a writable /dev, an ssh session comes in and is associated
> > with a /dev/ttyp[0-9] device file (the first available one).
> >
> >  is another option to mount the /dev/pts filesystem and, if so, would
> > dropbear try to grab one of *those* device files instead?  since
> > that's a pseudo filesystem, its device files should be writable, no?
> > even when /dev itself isn't.
>
> Hi Robert
>
> Couldn't you mount a ramfs over /dev and create the necessary device files
> in it? Should be easy enough to copy /dev to the ramfs first using tar or cpio.

  that's possible, but i'd like to know about the mountable /dev/pts
option first, since that seems like a lot less work.

rday
--

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Robert P. J. Day
Linux Consulting, Training and Annoying Kernel Pedantry:
    Have classroom, will lecture.

http://crashcourse.ca                          Waterloo, Ontario, CANADA
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