Install Bazel with Bazelisk

Operating system

LinuxmacOS

Prysm pins its Bazel version in the .bazelversion file at the root of the repository (currently 7.4.1). Bazelisk is a small launcher that reads this file, downloads that exact Bazel release, and runs it. Install Bazelisk as bazel, and you never manage Bazel versions by hand.

Before you begin

• A clone of the repository. See Overview.

The repository registers a hermetic C toolchain on Linux, so it doesn't use the system compiler.

You don't need to install Go for Bazel builds. Bazel downloads the Go SDK set in WORKSPACE (go_register_toolchains(go_version = "1.26.5")), which matches go.mod. Install Go separately only if your editor needs it.

Install Bazelisk

1. Install Bazelisk and make it available as bazel.

   Download the binary for your CPU from the Bazelisk releases and install it as /usr/local/bin/bazel. Use bazelisk-linux-arm64 on ARM64:

   curl -fL -o /tmp/bazel https://github.com/bazelbuild/bazelisk/releases/latest/download/bazelisk-linux-amd64 && sudo install -m 0755 /tmp/bazel /usr/local/bin/bazel

2. From the root of your clone, check the version. The first run downloads Bazel.

   bazel version

   You should see the Bazelisk version and the pinned Bazel release:

   Bazelisk version: <BAZELISK_VERSION>
   Build label: 7.4.1

Bazelisk picks the version from the .bazelversion of the directory you run it in, so a branch that bumps Bazel switches automatically on your next command. Outside a Bazel workspace, it falls back to the latest Bazel release, which is why bazel version must run inside the clone.

Check that it works

List the binary targets. This loads the repository and fetches the first dependencies:

bazel query 'kind(go_binary, //cmd/...)'

You should see:

//cmd/beacon-chain:beacon-chain
//cmd/client-stats:client-stats
//cmd/prysmctl:prysmctl
//cmd/validator:validator

Bazel settings in the repository

The root .bazelrc imports fragments from build/bazelrc/. A few defaults affect what you see day to day:

Setting	Effect
--keep_going	Builds and tests everything it can instead of stopping at the first failure.
test --test_output=errors	Prints the log of failing tests to the terminal.
--sandbox_default_allow_network=false	Build actions and tests have no network access unless the target is tagged requires-network.
--incompatible_strict_action_env	Actions get a fixed PATH, so changes to your shell environment don't invalidate the cache.

The named configs (release, minimal, debug and others) are covered in Build with Bazel and Unit tests.

Personal settings and a disk cache

Put your own flags in ~/.bazelrc, which Bazel reads in addition to the repository's .bazelrc and which isn't part of the repository. The most useful one is a disk cache, which keeps build results across bazel clean and across several clones:

~/.bazelrc

build --disk_cache=~/.cache/bazel-disk

Bazel's own output base lives under ~/.cache/bazel. The disk cache isn't pruned automatically; delete it when it gets too big.