Rocket.Chat/server/startup/migrations/v012.js

import { Meteor } from 'meteor/meteor';

import { Migrations } from '../../../app/migrations';
import { Users } from '../../../app/models';

Migrations.add({
	version: 12,
	up() {
		// Set oldest user as admin, if none exists yet
		const admin = Users.findOneAdmin(true, {
			fields: {
				_id: 1,
			},
		});

		if (!admin) {
			// get oldest user
			const oldestUser = Users.findOne({}, {
				fields: {
					username: 1,
				},
				sort: {
					createdAt: 1,
				},
			});

			if (oldestUser) {
				Meteor.users.update({
					_id: oldestUser._id,
				}, {
					$set: {
						admin: true,
					},
				});

				return console.log(`Set ${ oldestUser.username } as admin for being the oldest user`);
			}
		}
	},
});