Modify the number of ttys in CentOS 6

First, log in as root

1 – modify /etc/sysconfig/init
vi /etc/sysconfig/initand modify the following line:
ACTIVE_CONSOLES=/dev/tty[1-6]
to
ACTIVE_CONSOLES=/dev/tty[1-12]

2 – modify /etc/init/start-ttys.conf
copy the current start-ttys.conf configuration
cp /etc/init/start-ttys.conf /etc/init/start-ttys.override
This new override file will be automatically taken into account by Centos instead of the original one
vi /etc/init/start-ttys.override
and modify the following line
env ACTIVE_CONSOLES=/dev/tty[1-6]
by
env ACTIVE_CONSOLES=/dev/tty[1-12]

This modification will be handled at the next start.