Answer by proski for Install 64-bit kernel in 32-bit Ubuntu

The error indicates that Ubuntu does not provide a package named "linux-image-amd64".

I surmise this is due to the fact that the guide from where you picked the shell commands has been written for a Debian installation. Indeed, if you search on debian.org for this package, you'll get a positive result. This is not the case if you enter this package name on http://packages.ubuntu.com/

The last command should be

sudo apt-get install linux-image-generic:amd64

or (if you really care about latency)

sudo apt-get install linux-image-lowlatency:amd64

Please note that the 32-bit kernel will be removed. Also, some 64-bit userspace libraries will be installed. To see what apt-get will do to your system without actually touching your system, run apt-get with these options

sudo apt-get -Vs install linux-image-generic:amd64

If you want to retain your 32-bit kernel as a fallback, install a different kernel image, e.g. for your 14.04 (codename: trusty) try:

sudo apt-get install linux-generic-lts-trusty:amd64sudo apt-get install linux-generic-lts-utopic:amd64