This will enable VMotion on a VMKernel port. I am writing this one because it changed between verisons of ESX. This command uses the very useful vimsh.

ESX 3.0.x:
vimsh -n -e "/hostsvc/vmotion/vnic_set portgroup2"
portgroup# - Determined by the order of portgroup creation. The system automatically makes one to begin with.

ESX 3.5:
vimsh -n -e "/hostsvc/vmotion/vnic_set vmk0"
vmk# - Determined by the order of the VMKernel port creation. The first one created is '0'.

The service console memory should be increased if you are running apps other than the default install. This includes management agents, backups, etc. Here is a simple command that I ran across to accomplish this. It requires a reboot to take effect. I incorporate this in my kickstart script. Don't forget to set your swap partition to be 2x the Service Console memory.

See Current Setting:
The setting shown is in bytes (MB * 1024 * 1024)
vimsh -n -e "/hostsvc/memoryinfo"
serviceConsoleReserved - Current setting
serviceConsoleReservedCfg - Setting after next reboot

Set to 800MB with vimsh:
vimsh -n -e "/hostsvc/memoryinfo 838860800"

Set by manual edit of files:
mv -f /etc/vmware/esx.conf /tmp/esx.conf.bak
sed -e 's/boot\/memSize = \"272\"/boot\/memSize = \"512\"/g' /tmp/esx.conf.bak >> /etc/vmware/esx.conf

mv -f /boot/grub/grub.conf /tmp/grub.conf.bak
sed -e 's/uppermem 277504/uppermem 523264/g' -e 's/mem=272M/mem=512M/g' /tmp/grub.conf.bak >> /boot/grub/grub.conf

If you feel like setting it to the maximum of 800 MB.

mv -f /etc/vmware/esx.conf /tmp/esx.conf.bak
sed -e 's/boot\/memSize = \"272\"/boot\/memSize = \"800\"/g' /tmp/esx.conf.bak >> /etc/vmware/esx.conf

mv -f /boot/grub/grub.conf /tmp/grub.conf.bak
sed -e 's/uppermem 277504/uppermem 818176/g' -e 's/mem=272M/mem=800M/g' /tmp/grub.conf.bak >> /boot/grub/grub.conf