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 its things on a USB drive instead of in my ~/.cache folder. How can I tell bazel to do this?

score 18 · Accepted Answer · edited Jan 07 '21 at 11:07

18

Use the --output_user_root flag.

Example:

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

edited Jan 07 '21 at 11:07

wgumenyuk

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answered Mar 30 '17 at 11:17

László

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When trying this solution on an AWS instance, I met the warning like WARNING: Output base '/workspace/bazel/.cache/0d1ff2dcdcd5fe715305037694b909f9' is on NFS. This may lead to surprising failures and undetermined behavior. – Leo5188 May 28 '19 at 20:16
eh, the link now returns 404 page not found :( – Smankusors Aug 04 '20 at 20:44

score 5 · Answer 2 · answered Nov 23 '16 at 23:38

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

export TEST_TMPDIR=/path/to/directory

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.)

answered Nov 23 '16 at 23:38

Matt Kleinsmith

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Setting TEST_TMPDIR makes Bazel believe it's running inside of a test and will heavily limit its resource use, slowing down builds. – László Apr 18 '19 at 05:42
god bless you Matt! – Cupitor Feb 25 '20 at 17:01

score 2 · Answer 3 · answered Mar 03 '22 at 23:47

I symlinked ~/.cache/bazel to a directory on my other drive. Looks to be working so far. i.e.

ln -s /mnt/otherdrive/bazel_cache ~/.cache/bazel

I thought to move the old cache to avoid rebuilding, but I noticed symlinks to directories within the cache and didn't want to deal with transferring those so they pointed to the new directory as well. So I just deleted the old cache, symlinked, and rebuilt.

How can I make bazel use external storage when building?

3 Answers3