[ELDK] Read-only root filesystem, devices and root access

[Giuseppe Modugno]

Dear all,

I'm developing a read-only root filesystems facing many problems we 
already know.

In order to solve the problem of ptys (I'd like to use telnet) I made 
symbolic links
  /dev/ptyp0 ---> /tmpfs/dev/ptyp0
  /dev/ptyp1 ---> /tmpfs/dev/ptyp1
  ...
  /dev/ttyp0 ---> /tmpfs/dev/ttyp0
  /dev/ttyp1 ---> /tmpfs/dev/ttyp1
  ...
Of course, /tmpfs is a read-write tmpfs filesystem I populate in 
rc.sh.

Now I can telnet into the system without problems using a normal 
account. When I try to login as root, it works only for the first 
telnet connection and not for the second or the third.
The problem is pam_securetty, in fact in /var/log/messages:
---
Jan  1 00:09:19 hostname auth.warn PAM-securetty[686]: access denied: 
tty '/tmpfs/dev/ttyp1' is not secure !
---

In my /etc/securetty ttyp1 is really present, as ttyp0, ttyp2 and so 
on. I tried to add /tmpfs/dev/ttyp1 in /etc/securetty and it works!

Now I don't understand. May I use symbolic links in /etc/securetty?
If yes, I don't understand why ptyp1 in /etc/securetty doesn't work.
If no, I don't understand why ptyp0 in /etc/securetty really works.

Any suggestions?