How to use the child_process.execAsync function in child_process

const initSamba = async () => {

  const logConfigPath = '/etc/rsyslog.d/99-smbaudit.conf'
  const logConfig = 'LOCAL7.*    @127.0.0.1:3721'

  // update rsyslog config if necessary
  let config = null
  try { config = await fs.readFileAsync(logConfigPath) } catch (e) {debug('initSamba: Not find Samba service')}
  if (config !== logConfig) {
    await fs.writeFileAsync(logConfigPath, logConfig)  
    await child.execAsync('systemctl restart rsyslog')
  }

  await child.execAsync('systemctl start nmbd')
  await child.execAsync('systemctl start smbd')
}

hash.update(text)
    digest = hash.digest().toString('hex')

    // await mkdirpAsync(this.docDir)
    tmppath = path.join(this.tmpDir, digest)
    filepath = path.join(this.docDir, digest)
    try {
      let stats = await fs.lstatAsync(filepath)
      return digest  
    }
    catch (e) {
      if (e.code !== 'ENOENT') throw e
    }
      
    await writeFileToDiskAsync(tmppath, text)
    await child.execAsync(`chmod 444 ${tmppath}`)
    await fs.renameAsync(tmppath, filepath)
    return digest
  }

const probeWS215iAsync = async () => {

  try {
    await fs.statAsync('/proc/BOARD_io')
    let arr = await Promise.all([
      child.execAsync('dd if=/dev/mtd0ro bs=1 skip=1697760 count=11'),
      child.execAsync('dd if=/dev/mtd0ro bs=1 skip=1697664 count=20'),
      child.execAsync('dd if=/dev/mtd0ro bs=1 skip=1660976 count=6 | xxd -p')
    ])
    return {
      serial: arr[0].toString(),
      p2p: arr[1].toString(),
      mac: arr[2].trim().match(/.{2}/g).join(':')
    }
  } catch (e) {}
}

const addUnixUserAsync = async (username, uid) => {

  debug('addUnixUser', username, uid)
  let cmd = 'adduser --disabled-password --disabled-login --no-create-home --gecos ",,," ' + 
    `--uid ${uid} --gid 65534 ${username}`
  return child.execAsync(cmd)
}

function getInstalledTractorVersion () {
    info('Checking local "tractor" version...');
    return childProcess.execAsync(LOCAL_TRACTOR_VERSION_COMMAND)
    .then(local => {
        let { version } = JSON.parse(local).dependencies.tractor;
        info(`Local version of "tractor" is: ${version}`);
        return version;
    })
    .catch(() => {
        info('"tractor" is not installed.');
    });
}

return Promise.all([fs.writeFileAsync(newDest, contents, "utf8"),
                                fs.writeFileAsync(minDest, minified.code, "utf8")]);
        });
    }, {concurrency: 4});

    return Promise.all(
        [codecs, css, cp.execAsync("browserify src/audio/AudioPlayerBackend.js --standalone AudioPlayer > dist/worker/AudioPlayerWorker.js", execOpts).then(function() {
            return fs.readFileAsync("dist/worker/AudioPlayerWorker.js", "utf8");
        }).then(function(contents) {
            contents = "self.DEBUGGING = false;\n" + contents;
            var minified = UglifyJS.minify(contents, {
                fromString: true
            });
            return fs.writeFileAsync("dist/worker/AudioPlayerWorker.min.js", minified.code, "utf8");
        }),
        cp.execAsync("browserify src/audio/TrackAnalyzerBackend.js --standalone TrackAnalyzer > dist/worker/TrackAnalyzerWorker.js", execOpts).then(function() {
            return fs.readFileAsync("dist/worker/TrackAnalyzerWorker.js", "utf8");
        }).then(function(contents) {
            contents = "self.DEBUGGING = false;\n" + contents;
            var minified = UglifyJS.minify(contents, {
                fromString: true
            });
            return fs.writeFileAsync("dist/worker/TrackAnalyzerWorker.min.js", minified.code, "utf8");
        }),
        cp.execAsync("browserify src/application.js --standalone Application > dist/main.js", execOpts)
    ]);
});

function installTractor () {
    info('Installing "tractor"...');
    return childProcess.execAsync(INSTALL_DEPENDENCIES_COMMAND)
    .catch(() => error(`Couldn't install "tractor". Either run "tractor init" again, or install it manually by running "npm install tractor@latest --save-dev"`))
    .then(() => info('Installed "tractor".'));
}

}).then(function() {
    return cp.execAsync("mv dist/css/min/app-css-public.css dist/css/app-css-public.min.css", execOpts);
}).then(function() {
    return fs.readFileAsync("dist/css/min/critical.css", "utf8");

const addSmbUsersAsync = async (fusers) => {

  let text = fusers.map(u => `${u.unixname}:${u.uid}:` + 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX:' +
    `${u.md4}:[U          ]:${u.lct}:`).join('\n')

  debug('addSmbUsers', text)

  await mkdirpAsync('/run/wisnuc/smb')
  await fs.writeFileAsync('/run/wisnuc/smb/tmp', text)
  await child.execAsync('pdbedit -i smbpasswd:/run/wisnuc/smb/tmp')

  debug('addSmbUsers, after', await child.execAsync('pdbedit -Lw'))
}

contents = "self.DEBUGGING = false;\n" + contents;
            var minified = UglifyJS.minify(contents, {
                fromString: true
            });
            return fs.writeFileAsync("dist/worker/AudioPlayerWorker.min.js", minified.code, "utf8");
        }),
        cp.execAsync("browserify src/audio/TrackAnalyzerBackend.js --standalone TrackAnalyzer > dist/worker/TrackAnalyzerWorker.js", execOpts).then(function() {
            return fs.readFileAsync("dist/worker/TrackAnalyzerWorker.js", "utf8");
        }).then(function(contents) {
            contents = "self.DEBUGGING = false;\n" + contents;
            var minified = UglifyJS.minify(contents, {
                fromString: true
            });
            return fs.writeFileAsync("dist/worker/TrackAnalyzerWorker.min.js", minified.code, "utf8");
        }),
        cp.execAsync("browserify src/application.js --standalone Application > dist/main.js", execOpts)
    ]);
});