This repository contains hashes of build tools used by Chromium and related projects. The actual binaries are pulled from Google Storage, normally as part of a gclient hook. The repository is separate so that the shared build tools can be shared between the various Chromium-related projects without each one needing to maintain their own versionining of each binary. One uploads new versions of the tools using the 'gsutil' binary from the Google Storage SDK: https://developers.google.com/storage/docs/gsutil There is a checked-in version of gsutil as part of depot_tools. To initialize gsutil's credentials: python ~/depot_tools/third_party/gsutil/gsutil config That will give a URL which you should log into with your web browser. The username should be the one that is on the ACL for the "chromium-gn" bucket (probably your @google.com address). Contact the build team for help getting access if necessary. Copy the code back to the command line util. Ignore the project ID (it's OK to just leave blank when prompted). Instructions for how to upload the .sha1 digests of the GN binaries can be found at https://code.google.com/p/chromium/wiki/UpdateGNBinaries .