Ubuntu 10.04 32-bit - How to check if kernel is PAE-enabled?

Question

I know that 32-bit 10.04 enables PAE on installation when it detects 3+ GB RAM, but I'd like to know a way to manually check (i.e. in the terminal) that PAE is, in fact, enabled.

Answer 1

On current versions of Ubuntu on the 386 architecture, PAE is enabled on -generic-pae kernels but not on -generic or -virtual kernels, so you can check if the output uname -r ends with -pae. This isn't very robust though, since it depends on intimate knowledge of what Ubuntu uses for kernel options.

Some distributions provide the kernel configuration in /proc/config, so you can test with </proc/config fgrep -x CONFIG_X86_PAE=y. Ubuntu doesn't, but it does keep the kernel configuration in a well-known place, so you can test with </boot/config-$(uname -r) fgrep -x CONFIG_X86_PAE=y.

Note that grep -w pae /proc/cpuinfo tells you whether your processor supports PAE. The flag will be present whether the kernel supports PAE or not.

Answer 2

I just ran into this on a custom compiled kernel. This was how I got the answer:

First try to see if you have the file /proc/config.gz (you would have had to enable that in the config before compiling with: CONFIG_IKCONFIG which can be found under "General setup > Kernel .config support > Enable access to .config through /proc/config.gz"). If you do not see the file, you might need to:

# modprobe configs

(as root/sudo).

After that, run:

# cat /proc/config.gz |gunzip  > /tmp/config-$(uname -r).config

then:

# grep PAE /tmp/config-$(uname -r).config

If it says something like:

CONFIG_X86_PAE=y

That's your answer. If it is not compiled in, the grep will return nothing, or more likely something like:

# CONFIG_X86_PAE is not set

(Source: Linux: Get Kernel Config)

Answer 3

Run cat /proc/cpuinfo | grep -i PAE from the Commandline. If it returns PAE then the Kernel is PAE enabled. - @Gilles says this returns whether the CPU supports PAE, not the Kernel.

Another way to check is run uname -r - it should contain reference to PAE if the kernel is PAE enabled