How can I make bazel use external storage when building?

Question

When building certain code with bazel I'm running out of storage space. I'd like bazel to store it's things on a USB drive instead of in my ~/.cache folder. How can I tell bazel to do this?

Answer 1

Use the --output_user_root flag.

Example:

bazel --output_user_root=/path/to/directory build //foo:bar

Answer 2

You can change the outputRoot directory by changing the $TEST_TMPDIR variable.

export TEST_TMPDIR=/path/to/directory

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From the bazel docs:

The outputRoot directory is ~/.cache/bazel. (Unless $TEST_TMPDIR is set, as in a test of bazel itself, in which case this directory is used instead.)