How to Enable PAE

Ubuntu 10.04 LTS (Lucid Lynx)

Both the CD and DVD installer of Ubuntu 10.04 automatically installs the PAE enabled kernel if it detects more than 3 Gb of available memory. In the case of the liveCD, a working network connection is required, since the PAE enabled kernel packages are not present on the CD.

If you need to enable PAE manually, follow the instructions for Karmic below.

Ubuntu 9.10 (Karmic Koala)

The PAE enabled kernel can be installed using the Synaptic Package Manager (accessible from the System menu under Administration -> Synaptic Package Manager): The relevant packages are called "linux-generic-pae" and "linux-headers-generic-pae" and should be easily found with a search for "pae".

Alternatively they can be installed using either apt-get or aptitude through the terminal:

sudo aptitude install linux-generic-pae linux-headers-generic-pae

After a reboot the PAE kernel should be booted as the default option in the GRUB boot menu.

To confirm that PAE was enabled correctly you can use the system monitor form the System menu under Administration -> System Monitor. The first tab shows usable memory.

DVD installer

If installing from the DVD version of Ubuntu 9.10 (both live and alternate), it will automatically install the PAE enabled kernel if it detects more than 3 Gb of available memory, it should work straight out of the box.

Earlier versions (Ubuntu 9.04 and earlier)

Prior to Ubuntu 9.10, there are no specific PAE-enabled kernels for the desktop version, however the server kernels comes with PAE enabled. So by installing and running these, PAE can be used in the desktop version of ubuntu.

First, turn off any restricted drivers. We'll turn them back on once we're done, but if you don't turn them off first, X won't start, and that's bad. Just go into System -> Administration -> Hardware Drivers and turn off your graphics drivers.

Next we just install the server kernel:

sudo aptitude install linux-server linux-headers-server

After a reboot the PAE kernel should be booted as the default option in the GRUB boot menu. Once you're at the desktop, re-enable your restricted drivers (System -> Administration -> Hardware Drivers).

To confirm that PAE was enabled correctly you can use the system monitor form the System menu under Administration -> System Monitor. The first tab shows usable memory.

Removing non-PAE kernels

If PAE was successfully enabled you may want to remove the meta-packages for the normal kernel, to disable unecessary updates to the non-PAE kernels

sudo aptitude remove linux-generic linux-image-generic linux-headers-generic

If you want to remove all of the old kernels from your boot menu, it seems like you have to do it all manually:

sudo aptitude remove linux-image-<version number>-generic linux-headers-<version number>-generic

Something went wrong

If something went wrong, just remove the PAE kernel packages using either synaptic or apt-get/aptitude. If you did not specifically remove the non-PAE kernel packages, they should still be present on the system and automatically selected as the default when the PAE kernel is removed.

Ubuntu 9.10 and later

The relevant packages are:

linux-image-generic-pae  linux-image-<version number>-generic-pae linux-headers-generic-pae linux-headers-<version number>-generic-pae

Earlier versions (Ubuntu 9.04 and earlier)

Make sure to turn off the restricted drivers when switching between them.

The relevant packages are:

linux-server linux-headers-server linux-image-server linux-image-<version number>-server linux-headers-<version number>-server