The Dells come with a Remote Access Controller, but with remote access Dell means only with windows ...

The remote video console only works with an ActiveX or with a special RPM client, so no mac and no Ubuntu, (Sun X4100 has a java remote video console that just work everywhere, think about it).

A good solution is to activate the serial port of the guest os then route it to the SSH access of the RAC card.

To do that, modify your grub config to make the grub menu appears on serial console:
Edit /boot/grub/menu.lst and add this after default 0

default         0

# show grub on serial console for dell 
serial --unit=1 --speed=57600
terminal --timeout=10 serial

Now you also need to make your linux kernel log everything on the serial port, to do that in the /boot/grub/menu.lst file again, add console=ttyS1,57600 right after all kernel entries like this:

title           Ubuntu, kernel 2.6.20-15-generic
root            (hd0,2)
kernel          /boot/vmlinuz-2.6.20-15-generic root=UUID=c13549c7-0ebc-4840-a01b-15e47a68f92a ro  console=ttyS1,57600
initrd          /boot/initrd.img-2.6.20-15-generic
quiet
savedefault

Great now you also need to give the console access to the linux for that, create a new file in /etc/event.d/ttyS1 and put this:

# ttyS1 - getty
#
# This service maintains a getty on tty1 from the point the system is
# started until it is shut down again.

start on runlevel 2
start on runlevel 3
start on runlevel 4
start on runlevel 5

stop on runlevel 0
stop on runlevel 1
stop on runlevel 6

respawn
exec /sbin/getty -h  -L 57600 ttyS1 ansi

Add ttyS1 to the /etc/securetty file to have a root access, (which should not be usefull on Ubuntu).

Ssh your RAC ip (the one with the web interface), and enable console access for ssh (just one time):

racadm config -g cfgSerial -o cfgSerialSshEnable 1

You can now connect to the serial port everytime you want via the ssh access of the RAC, with the command connect com2, and login to your dead linux after you submit a wonderful new iptables rule ;).

Ps: ttyS1 is not a mistake, the rac serial port is com2.