Thank you very much Joe and Florian for your response.
Actually this is part of a Embedded system. So my total
root file system will be in flash which is read only.
So I can not make root read write.
I have another RW root also. but there is no problem like
Unable to change tty /dev/tty1 : Read Only file System.It is working
Now regarding Hard Disk error,this same system is running in 2 machines
so I think this is not problem of Hard Disk. When I remounted this
Read only root as RW using 'mount -o remount,rw /' and again try to
login then no problem it is working fine.
I have tried to change TTYGRP and TTYPERM in /etc/login.defs as login proces using these 2 variables.
I want to know due to this error is there any harm or problem in console operation?
Ok waiting for your kind response.
Thanking you in advance.