Why would you do this?
If there was an update that made your system non-bootable and they have fixed it in the repositories, you can use the Live CD to run apt-get to get the new files to fix your system.
In my case, wireless was functional before (and during) the installation, but was not working on installed system, so I had to (connect to the internet) and install bunch of things to get it working.
How to do it
Boot the Ubuntu Live CD (or USB Stick), press Ctrl-Alt-F1:
# mount /dev/hda1 /mnt # chroot /mnt # apt-get update # apt-get upgrade
Other things you need to do:
# exit # umount /mnt
First, you need to figure the partition notation for your ‘/’ drive which looks like ‘sda1’, ‘sda2’ etc:
# fdisk -l
For creating the Chroot, you need to run commands written bellow one-by-one Note: ‘sdXY’ is your ‘/’ partition.
# mkdir /mnt/temp # mount /dev/sdXY /mnt/temp # for i in /dev /dev/pts /proc /sys; do sudo mount -B $i /mnt/temp$i; done # cp /etc/resolv.conf /mnt/temp/etc/resolv.conf # chroot /mnt/temp
After you’ve finished working type ‘exit’ in the Terminal to exit the Chroot. Then un-mount the previously mounted locations by running this command:
# for i in /dev/pts /dev /proc /sys; do sudo umount /mnt/temp$i ; done