docs: function(cid) {
      // Validate input.
      return Promise.try(function() {
        if (typeof cid !== 'string') {
          throw new VError('Invalid cid: ' + pp(cid));
        }
      })
      // Inspect.
      .then(function() {
        return inspect(cid);
      })
      .then(function(data) {
        return _.get(data, 'State.Running', false);
      })
      // If the container no longer exists, return false since it isn't running.
      // This will prevent a race condition from happening.
      // Wrap errors.
      .catch(function(err) {
        var expected = format('The container "\'%s\'" does not exist!', cid);
        if (_.endsWith(err.message, expected)) {
          return false;
        } else {
          // Wrap errors.
          throw new VError(err, 'Error querying isRunning: "%s".', pp(cid));
        }
      });
    }