It's burning every build on try that it can get its hands on (and that's a lot) like https://tbpl.mozilla.org/php/getParsedLog.php?id=15486062&tree=Try State Changed: unpacking root cache DEBUG: Executing command: ['tar', '--use-compress-program', 'pigz', '-xf', '/builds/mock_mozilla/cache/mozilla-centos6-x86_64/root_cache/cache.tar.gz', '-C', '/builds/mock_mozilla/mozilla-centos6-x86_64/root/'] DEBUG: pigz abort: corrupted input -- invalid deflate data: <stdin> DEBUG: tar: Unexpected EOF in archive DEBUG: tar: Unexpected EOF in archive DEBUG: tar: Error is not recoverable: exiting now DEBUG: Child return code was: 2 ERROR: Command failed. See logs for output. # ['tar', '--use-compress-program', 'pigz', '-xf', '/builds/mock_mozilla/cache/mozilla-centos6-x86_64/root_cache/cache.tar.gz', '-C', '/builds/mock_mozilla/mozilla-centos6-x86_64/root/'] DEBUG: kill orphans program finished with exit code 2

I've moved the /builds/mock_mozilla/cache/mozilla-centos6-x86_64/root_cache/cache.tar.gz to ~/, and removed the rootcache.lock along side it. I think mock will rebuild the cache next time it needs the 64bit environment (a 64bit desktop build). Leaving open to verify.

Verified in a rebuilt 'Linux x86-64 try build' that the mock_init step worked, and the cache was recreated.