How to check if Linux user namespaces are supported by current OS kernel

Question

After doing some reading, I found that Linux user namespaces are generally supported in Linux versions >= 3.8. However, there's a possibility that user namespaces are disabled on a given OS, making the check for kernel versions unreliable. Is there a robust way to check if the current OS I'm using supports user namespaces and has it available to use?

Answer 1

You could check if your current process' /proc/[pid]/ns/ directory has a file called user:

ls /proc/self/ns