Question

How to determine whether I run a 32bit or 64bit Ubuntu install?

Answer 1

Did you try uname -m ?

It seems like the uname -m actually gives

• x86_64 when it is an kernel 64 bits
• i686 for 32 bits kernel

Otherwise, not for the Linux kernel, but for the CPU, you type:

cat /proc/cpuinfo

or:

grep flags /proc/cpuinfo

Under "flags" parameter, you will see various values. Among them, one is named "tm(transparent mode)" or "rm(real mode)" or "lm(long mode)"

• rm means: 16 bit processor
• tm means: 32 bit processor
• lm means: 64 bit processor

Note: you can have a 64-bit CPU with a 32-bit kernel installed"

Source.