Initramfs
From Lolly's Wiki
Adding binaries to the initial ram disk in ubuntu
Adding vi to initramfs
$ sudo cat >/etc/initramfs-tools/hooks/vi <<EOH
#!/bin/sh
PREREQ=""
prereqs()
{
echo "$PREREQ"
}
case $1 in
prereqs)
prereqs
exit 0
;;
esac
. /usr/share/initramfs-tools/hook-functions
# Begin real processing below this line
copy_exec /usr/bin/vim.basic /bin
exit 0
EOH
$ sudo update-initramfs -k $(uname -r) -u