balena-supervisor/src/migrations/M00001.js

const fs = require('fs');
const configJsonPath = process.env.CONFIG_MOUNT_POINT;

const { checkTruthy } = require('../lib/validation');

exports.up = function(knex, Promise) {
	return knex('config')
		.where({ key: 'localMode' })
		.select('value')
		.then(results => {
			if (results.length === 0) {
				// We don't need to do anything
				return;
			}

			let value = checkTruthy(results[0].value);
			value = value != null ? value : false;

			return new Promise(resolve => {
				if (!configJsonPath) {
					console.log(
						'Unable to locate config.json! Things may fail unexpectedly!',
					);
					resolve();
					return;
				}
				fs.readFile(configJsonPath, (err, data) => {
					if (err) {
						console.log(
							'Failed to read config.json! Things may fail unexpectedly!',
						);
						resolve();
						return;
					}
					try {
						const parsed = JSON.parse(data.toString());
						// Assign the local mode value
						parsed.localMode = value;

						fs.writeFile(configJsonPath, JSON.stringify(parsed), err2 => {
							if (err2) {
								console.log(
									'Failed to write config.json! Things may fail unexpectedly!',
								);
								return;
							}
							resolve();
						});
					} catch (e) {
						console.log(
							'Failed to parse config.json! Things may fail unexpectedly!',
						);
						resolve();
					}
				});
			}).then(() => {
				return knex('config')
					.where('key', 'localMode')
					.del();
			});
		});
};

exports.down = function(knex, Promise) {
	return Promise.reject(new Error('Not Implemented'));
};