Grub:
cat /etc/default/grub
# If you change this file, run 'update-grub' afterwards to update
# /boot/grub/grub.cfg.
GRUB_DEFAULT=0
GRUB_TIMEOUT=1
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX="console=tty0 console=ttyS0,115200n8"
# Uncomment to disable graphical terminal (grub-pc only)
GRUB_TERMINAL=serial
GRUB_SERIAL_COMMAND="serial --speed=115200 --unit=0 --word=8 --parity=no --stop=1"
# The resolution used on graphical terminal
# note that you can use only modes which your graphic card supports via VBE
# you can see them in real GRUB with the command `vbeinfo'
#GRUB_GFXMODE=640x480
# Uncomment if you don't want GRUB to pass "root=UUID=xxx" parameter to Linux
#GRUB_DISABLE_LINUX_UUID=true
Enable TTYS0:
cat /etc/default/grub
# If you change this file, run 'update-grub' afterwards to update
# /boot/grub/grub.cfg.
GRUB_DEFAULT=0
GRUB_TIMEOUT=1
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX="console=tty0 console=ttyS0,115200n8"
# Uncomment to disable graphical terminal (grub-pc only)
GRUB_TERMINAL=serial
GRUB_SERIAL_COMMAND="serial --speed=115200 --unit=0 --word=8 --parity=no --stop=1"
# The resolution used on graphical terminal
# note that you can use only modes which your graphic card supports via VBE
# you can see them in real GRUB with the command `vbeinfo'
#GRUB_GFXMODE=640x480
# Uncomment if you don't want GRUB to pass "root=UUID=xxx" parameter to Linux
#GRUB_DISABLE_LINUX_UUID=true
Enable TTYS0:
You definitely need to enable the serial console in the guest machine before being able to connect. The correct way is described here: https://help.ubuntu.com/community/SerialConsoleHowto
Recent Ubuntu versions use Upstart tasks and services so you should add an Upstart task as
/etc/init/ttyS0.conf, containing the following:# ttyS0 - getty
#
# This service maintains a getty on ttyS0 from the point the system is
# started until it is shut down again.
start on stopped rc or RUNLEVEL=[2345]
stop on runlevel [!2345]
respawn
exec /sbin/getty -L 115200 ttyS0 vt102
Start it this way:
$ sudo start ttyS0
After that you should be able to connect to the serial console from the host. Don't forget to press Enter once connected.