how to run dropbear on a system with a R/O /dev? [SOLVED!]
Robert P. J. Day
rpjday at crashcourse.ca
Wed Dec 24 05:12:02 WST 2008
On Tue, 23 Dec 2008, Matt Johnston wrote:
> On Mon, Dec 22, 2008 at 10:51:26AM -0500, Robert P. J. Day wrote:
> > > We do have /dev/pts mounted, that may or may not make a difference
> > > (didn't check the code).
> >
> > i may do that at the earliest possible opportunity, but here's
> > what's happening. certainly, without mounting /dev/pts, i expect
> > a login failure since all of /dev is read-only.
> >
> > however, after i mount /dev/pts RW, i can see that i have two
> > char device files under there: /dev/pts[01]. and i've verified i
> > can change their permissions with "chmod". so that's a good sign
> > -- that the contents under /dev/pts are modifiable, at least to
> > that extent.
> >
> > however, when i try to ssh into that system from elsewhere and i
> > watch the destination system /var/log/messages, i can see that the
> > password authentication succeeds, after which i get an
> > authpriv.warn log message complaining about
> > syslogin_perform_logout: logout(pts/2) returned an error: No such
> > file or directory
>
> Devices in /dev/pts get "automatically" created by the
> openpty() call made by Dropbear - you don't create files
> there yourself. The usual tool I use for debugging things
> like this is strace - run "strace -f" on the main Dropbear
> process, if it's available. Are there any other log messages
> suggesting why it's failing?
i hacked into the flashed system, and simply added a mount of the
/dev/pts filesystem and, upon reboot, an attempt to ssh to the system
caused dropbear to allocate /dev/pts/1. so this is progress.
apparently, mounting that filesystem manually before didn't work, but
having it mounted as part of the normal boot process was sufficient.
rday
--
========================================================================
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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