For our web management service we also performance website backups in a timely manner by using our own FTP server. This guide is written on how we configured VSFTP (A recognized FTP server in Linux distros such as Ubuntu) to handle multiple websites.
If your Yii2 web app does not work for user auto login, then you must have missed these steps. Check them to solve your problem.
Make sure your User Identity class overrides the necessary methods.
findIdentity, findIdentityByAccessToken, getId, getAuthKey, validateAuthKey
Then when the user logins, you have to...