Unitech/pm2 · error · Error

Interpreter is NOT AVAILABLE in PATH. (type 'which ' to…

Error message

Interpreter ${app.exec_interpreter} is NOT AVAILABLE in PATH. (type 'which ${app.exec_interpreter}' to double check.)

What it means

Before launching an app, PM2 verifies the configured exec_interpreter is resolvable via which(). If not found it throws to prevent a silent spawn failure — except for the special 'node' case, which falls back to the bundled node interpreter. Any other missing interpreter aborts.

Solutions

1. Install the interpreter and ensure it is on PATH for the PM2 daemon, then restart the daemon (pm2 kill && pm2 resurrect).
2. Reference the interpreter by absolute path.
3. Set interpreter:'none' if the script is directly executable.
4. For node-based apps use interpreter:'node' to hit the bundled-node fallback.

Example fix

// before
{ script: 'main.py', interpreter: 'python3' }
// after
{ script: 'main.py', interpreter: '/usr/bin/python3' }

const which = require('which');
function resolveInterpreter(interp) {
  if (!interp || interp === 'none') return interp;
  if (which(interp, { nothrow: true }) == null && interp !== 'node') {
    throw new Error(`Interpreter '${interp}' not found on PATH; install it or use an absolute path`);
  }
  return interp;
}
app.exec_interpreter = resolveInterpreter(app.exec_interpreter);

const interpreterAvailable = (i) => !i || i === 'none' || i === 'node' || which(i, { nothrow: true }) != null;

When it happens

Trigger: Setting interpreter to a runtime that isn't installed or isn't on the PM2 daemon's PATH (python3, php, ruby, deno, ts-node), or misspelling the interpreter name.

Common situations: Container missing the runtime; local dev where the interpreter is installed via nvm/asdf but PATH isn't propagated to the (already-running) PM2 daemon; typo in interpreter.

AI-assisted analysis of Unitech/pm2@31adee8048 (2026-08-13). Data as JSON: /api/errors/1e6584d1a2b8cf73. Report an issue: GitHub.

Appendix: source

Thrown at lib/Common.js:464

  if (app.exec_interpreter.indexOf('python') > -1)
    app.env.PYTHONUNBUFFERED = '1'

  if (app.exec_interpreter == 'lsc') {
    app.exec_interpreter = path.resolve(__dirname, '../node_modules/.bin/lsc');
  }

  if (app.exec_interpreter == 'coffee') {
    app.exec_interpreter = path.resolve(__dirname, '../node_modules/.bin/coffee');
  }

  if (app.exec_interpreter != 'none' && which(app.exec_interpreter) == null) {
    // If node is not present
    if (app.exec_interpreter == 'node') {
      Common.warn(`Using builtin node.js version on version ${process.version}`)
      app.exec_interpreter = cst.BUILTIN_NODE_PATH
    }
    else
      throw new Error(`Interpreter ${app.exec_interpreter} is NOT AVAILABLE in PATH. (type 'which ${app.exec_interpreter}' to double check.)`)
  }

  return app;
};

Common.deepCopy = Common.serialize = Common.clone = function(obj) {
  if (obj === null || obj === undefined) return {};
  return fclone(obj);
};

Common.errMod = function(msg) {
  if (process.env.PM2_SILENT || process.env.PM2_PROGRAMMATIC === 'true') return false;
  if (msg instanceof Error)
    return console.error(msg.message);
  return console.error(`${cst.PREFIX_MSG_MOD_ERR}${msg}`);
}

Common.err = function(msg) {

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