Docker container has no TMPDIR environmental variable

Question

I'm running a Node app on node:6.3-wheezy. I noticed that os.tmpdir() returns the path to the project directory, which is probably just PWD. When I run env in the container, I see that there is no TMPDIR environmental variable. Why is this? I'd like the system to establish it's own temp directory rather than setting it myself.

Answer 1

Because TMPDIR has not been set in the container environment.

The only environment variables docker will set are

• HOME - Set based on the value of USER
• HOSTNAME - The hostname associated with the container
• PATH - Includes common directories, such as : /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
• TERM - xterm if the container is allocated a pseudo-TTY (interactive input)

Anything else is image specific and up to you.

You can set them via an ENV step in a Dockerfile if needed or on the command line with --env TMDIR=x