If you cam't login to linux machine using console there might a chance that there is something wrong with console file "/etc/securetty" and also verify the the "/etc/pam.d" files. Sample Configuration of /etc/securetty file is given below :
[root@server1 ~]# cat /etc/securetty
# /etc/securetty: list of terminals on which root is allowed to login.
# See securetty(5) and login(1).
console
vc/1
vc/2
vc/3
vc/4
vc/5
vc/6
vc/7
vc/8
vc/9
vc/10
vc/11
tty1
tty2
tty3
tty4
tty5
tty6
tty7
tty8
tty9
tty10
tty11
xvc0
hvc0