Originally Posted by nirmalsethy
i am using redhat 4. somehow /etc/passwd (also passwd-)and shadow are modified manually.so i can't login.only i can enter in singe user mode, but i can't start x session.Can i solve the problem without re-installation.
Yes. Log in as single-user (root). Check the permissions on /etc/passwd and /etc/shadow. From what I remember, shadow should be owned by root:root, permissions 600. passwd root:root, 644. Reboot and see if it works.
Also, you have some MAJOR security issues on your system, if you weren't the one who did this....