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Binary Installer & Install.sh Script

binary-installer/README.md

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Binary Installer & Install.sh Script

This project is responible for creating the built binaries that auto-update framework builds, as well as install.sh script that is used in the curl command we provide for installation.

Installing With Curl

To use the install script that is currently deployed, you would run the following curl command from your command prompt,

bash
curl -o- -L https://install.serverless.com | bash

This installs the most recent launcher binary. The framework itself is downloaded the first time you run serverless, so expect that initial invocation to fetch the latest release. By default the serverless command will check for a new update every 24 hours. If however you want to force a download of a new version you can set the environment variable SERVERLESS_FRAMEWORK_FORCE_UPDATE=true and then anytime you run serverless it will check if a new version is available and download it.

Custom CA Certificates

For environments that use private CAs or TLS-intercepting proxies, the installer and framework downloads can trust additional certificate authorities via the following environment variables:

  • NODE_EXTRA_CA_CERTS: Path to a PEM file containing one or more root CAs.
  • SSL_CERT_FILE: Path to a PEM file containing one or more root CAs.
  • SSL_CERT_DIR: Path list (separated by your OS path list separator, e.g. : on Unix or ; on Windows) of directories containing PEM-encoded CA files.

These certificates are added to the system trust store used by the installer’s HTTP client.

How the Binary Installer Works

High-level flow

  1. Startup and environment prep (main.go):
    • Optionally configures extra CA certificates when SLS_DISABLE_EXTRA_CA_CERTS is set to a non-"false" value (see Custom CA Certificates section).
    • Ensures ~/.serverless/binaries exists.
    • If invoked as serverless update, downloads and swaps the installer binary in place.
    • If a local v3 node_modules/serverless is present, defers execution to it for backwards compatibility.
  2. Config resolution:
    • Determines the service config path from --config/-c flags or scans the CWD for supported filenames (serverless.*, serverless-compose.*, serverless.containers.*, serverless.ai.*).
  3. Version resolution and download (src/version.go):
    • Reads frameworkVersion from the service config (supports YAML, JSON, and generic JS/TS via regex).
    • Resolves the framework release to use:
      • Canary channel (frameworkVersion: canary or canary-<commit-short-sha>): fetches the latest/specified canary release metadata from the install host.
      • Stable channel: fetches the versions index and picks the best matching supported version (exact or semver range).
    • Installs the selected framework release under ~/.serverless/releases/<version> by downloading an archive and running npm install in the extracted package/ folder.
  4. Node checks and execution:
    • Verifies node and npm exist and Node.js is >= 18.
    • Launches node <releasePath>/package/dist/sf-core.js with the original CLI arguments.

Files saved locally

  • ~/.serverless/binaries/metadata.json
    • Fields: { "version": string, "updateLastChecked": ISO8601 }
    • Purpose: updateLastChecked throttles how often the versions index is re-fetched. version is informational (printed on install) and not used for logic.
  • ~/.serverless/binaries/versions.json
    • Cached copy of the versions index (supportedVersions, blockedVersions).
    • Used to resolve the latest supported version or a best match for ranges when fresh (see throttling below). Falls back when network errors occur.
  • ~/.serverless/releases/<version>/
    • Extracted framework release contents with package/ and installed dependencies.
    • The CLI entry executed is package/dist/sf-core.js.

HTTP calls and throttling

  • Versions index (stable channel):
    • URL: https://install.serverless.com/versions.json
    • Throttling: at most once per 24 hours, keyed by metadata.json.updateLastChecked.
    • Cache: on successful fetch, response is written to ~/.serverless/binaries/versions.json. On errors, a present cache is used as a fallback.
  • Canary release metadata (canary channel):
    • URL: https://install.serverless-dev.com/releases.json (for latest canary). For pinned canary, the version is taken from config directly.
    • Throttling: not throttled; only requested when using the canary channel.
  • Release archives:
    • Stable: https://install.serverless.com/archives/serverless-<version>.tgz
    • Canary: https://install.serverless-dev.com/archives/<canary-version>.tgz (or canary-<x>.tgz for latest)
    • Downloaded when the target release directory does not exist or when explicitly forced (see below). On success, metadata.json is updated.
  • Installer self-update:
    • URL: <install host>/installer-builds/serverless-<os>-<arch>
    • Only when running serverless update.

Update policy (when downloads happen)

  • Framework releases are downloaded when:
    • The resolved ~/.serverless/releases/<version> directory is missing, or
    • The user explicitly forces an update via serverless update or SERVERLESS_FRAMEWORK_FORCE_UPDATE=true.
  • The 24h throttle only applies to refreshing the versions index, not installing releases.

Environment variables

  • SERVERLESS_FRAMEWORK_FORCE_UPDATE
    • When set, forces a fresh version resolution and release download even if a matching release directory exists.
  • SLS_DISABLE_EXTRA_CA_CERTS
    • When set to any value other than "false", augments the HTTP client trust store with additional CAs from the variables below.
  • NODE_EXTRA_CA_CERTS, SSL_CERT_FILE, SSL_CERT_DIR
    • Standard Node/OpenSSL variables used to provide additional root CAs (see Custom CA Certificates).
  • CI
    • When present, sets a flag that influences whether an auto-update suggestion is printed when no frameworkVersion is specified.

Requirements

  • Node.js >= 18 and npm must be available on PATH.
  • Network access to the installer hosts:
    • https://install.serverless.com (stable releases and versions index)
    • https://install.serverless-dev.com (canary channel)

Error handling and fallbacks

  • If fetching the versions index fails, the installer will attempt to use the cached versions.json if present.
  • If parsing the versions index fails, a cached copy is used if available.
  • If a requested canary metadata fetch fails or returns malformed JSON, the command fails with a clear error message.
  • If npm install fails during release installation, combined output and exit code are surfaced to stderr and the process exits non-zero.

Supported configs and resolution rules

  • frameworkVersion can be specified in YAML (serverless.yml), JSON (serverless.json), or inferred from JS/TS (serverless.js, serverless.ts, serverless.cjs). For JS/TS, a simple regex extracts frameworkVersion: 'x.y.z'.
  • Constraints (e.g., ^4.0.0) are matched against the supported list from versions.json. Exact blocked versions are warned about but still honored if requested.
  • frameworkVersion: canary opts into the canary channel; canary-<commit-short-sha> pins a canary build directly.