Read-only root-filesystem

Hi all,
Does the dropbear-ssh needs writable root-filesystem to run correctly.
I set my file-system as read-only (which i ultimately wants to) and it
fails giving the following error.

====================
TRACE: continue recv_msg_channel_request: session request
TRACE: enter chansessionrequest
TRACE: type is shell
TRACE: enter sessioncommand
TRACE: enter ptycommand
[147] Mar 23 04:51:57 no pty was allocated, couldn't execute
========================

It works ok when i change the root-filesystem as the read-write.
Apparently due to the /dev/pty* ?.

I am running the default dropbear found in the uClinux-dist
distribution with my microblaze as the processor. Please let me know
how i can run the dropbear with the read-only root file system.

Appreciate your reply.

Thnx
- Prasad