1. Centos6 case
Centos 6 use upstart for configuration of serial consoles (terminals). You can find tip on it in the /etc/inittab configuration file.
Content of default Centos 6 /etc/inittab :
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# cat /etc/inittab
# inittab is only used by upstart for the default runlevel.
#
# ADDING OTHER CONFIGURATION HERE WILL HAVE NO EFFECT ON YOUR SYSTEM.
#
# System initialization is started by /etc/init/rcS.conf
#
# Individual runlevels are started by /etc/init/rc.conf
#
# Ctrl-Alt-Delete is handled by /etc/init/control-alt-delete.conf
#
# Terminal gettys are handled by /etc/init/tty.conf and /etc/init/serial.conf,
# with configuration in /etc/sysconfig/init.
#
# For information on how to write upstart event handlers, or how
# upstart works, see init(5), init(8), and initctl(8).
#
# Default runlevel. The runlevels used are:
# 0 - halt (Do NOT set initdefault to this)
# 1 - Single user mode
# 2 - Multiuser, without NFS (The same as 3, if you do not have networking)
# 3 - Full multiuser mode
# 4 - unused
# 5 - X11
# 6 - reboot (Do NOT set initdefault to this)
#
id:3:initdefault:
Upstart configuration files are stored in /etc/init directory:
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# ls -1 /etc/init/*
/etc/init/control-alt-delete.conf
/etc/init/init-system-dbus.conf
/etc/init/kexec-disable.conf
/etc/init/plymouth-shutdown.conf
/etc/init/prefdm.conf
/etc/init/quit-plymouth.conf
/etc/init/rc.conf
/etc/init/rcS.conf
/etc/init/rcS-emergency.conf
/etc/init/rcS-sulogin.conf
/etc/init/serial.conf
/etc/init/splash-manager.conf
/etc/init/start-ttys.conf
/etc/init/tty.conf
We will need to create /etc/init/ttyS0.conf configuration file with the following content for a new TTY device:
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# ttyS0 - mingetty
#
# This service maintains a mingetty on ttyS0.
stop on runlevel [S016]
start on runlevel [2345]
respawn
instance /dev/ttyS0
exec /sbin/mingetty --autologin root --noclear ttyS0
Add ttyS0 device to the list of of tty lines on which root is allowed to login :
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echo "ttyS0" >> /etc/securetty
Start it:
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# initctl start ttyS0
ttyS0 (/dev/ttyS0) start/running, process 27100
Configure the guest kernel settings in the guest /boot/grub/grub.conf and append console=/dev/ttyS0 option to the default kernel.
Reboot KVM domain to apply new settings. Check 'virsh console' work:
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# virsh console kvm101
Connected to domain kvm101
Escape character is ^]
CentOS release 6.3 (Final)
Kernel 2.6.32-279.19.1.el6.i686 on an i686
srv1 login:
2. Centos5 case
Centos 5 do not use upstart, therefore configuration is a bit simplier.
We need to add definition of console device in /etc/inittab:
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7:2345:respawn:/sbin/mingetty --autologin root --noclear ttyS0
Add ttyS0 device to the list of of tty lines on which root is allowed to login :
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echo "ttyS0" >> /etc/securetty
Append console=/dev/ttyS0 option to the default kernel in /boot/grub/grub.conf.
Reboot KVM domain to apply new settings. Check 'virsh console' work.
Similar steps can be used for Xen domains and correct work of 'xm console' / 'xl console'.
