User Backup Checker

Integrity checker for user backups performed via Synology Drive.

User Backup Checker (UBC) is a backend script for server administrators that warns them about users whose Synology Drive tool no longer performs backups. Synology Drive is a precious tool enabling multiple users to perform backups and synchronize files to a central Synology server. However, server administrators have no tool that actively alerts them when specific users stop performing backups, for example, because they forget to unpause Synology Drive or it can no longer reach the server after they change their passwords. UBC periodically creates a report with the latest backup dates of users for administrators. Optionally, it can automatically send emails to users with outdated backups and notify them about the problem.

UBC follows these design philosophies:

1. Minimum configuration effort:
   1. Dependencies only on Python 3.8 standard library, which comes pre-installed on newer Synology DSM versions.
   2. Single-file solution (no caches or config files)
   3. UBC is read-only and does neither modify nor create any files. It does not store databases, backup histories, or protocols.
      • Exceptions are actions the runtime environment performs outside UBC, such as Python automatically creating __pycache__/ or server admins configuring log protocols on DSM to store UBC reports over time.
   4. Periodic execution: UBC can be automated using Synology's default Task Scheduler. It does not require a continuous backup supervision process.
2. Supports local and domain users.
3. Privacy-focused: UBC does not collect usage data. UBC itself does not communicate with anything outside the server except for the emails to server admins and users.

UBC detects two types of issues in user backups:

1. Outdated backups: If the most recent modification date of any file in a user's backup directory is older than a specified number of days, UBC reports the user's backup as outdated.
2. Future-dated files in backups: If the most recent modification date of any file in a user's backup directory is in the future, UBC reports this user as future-dated. This scenario may, for example, arise when a user sets timestamps manually or when checking OS-related applications. However, such future-dated timestamps may confuse UBC's backup recency-detection algorithm. This algorithm determines whether the newest file's modification date is not older than a given number of days. As a result, a future-dated timestamp could wrongly appear recent for a significant period, potentially hundreds of years, thereby shadowing the user's actual backup process. To avoid misclassifications, UBC reports such users in a separate category.

UBC is a third-party script that has no association with Synology.

Setup

Follow these steps to set up UBC on a Synology server. To complete this setup, you need Synology server admin privileges. Note that the optional email notifications for users with outdated backups have to be configured separately, see Configuration.

1. Open ubc/user_backup_checker.py in a text editor and adjust the settings to your preferences. See also Configuration for the details.
2. Log in to Synology DSM with the admin account intended to run UBC.
   • Ensure this account has read permissions for all user backup directories; otherwise, UBC cannot validate backups.
3. Open File Station and navigate to the directory where you wish to store the UBC script. For example, let's use /volume1/homes/admin/.
4. Upload ubc/user_backup_checker.py to this directory. The script path should now be: /volume1/homes/admin/user_backup_checker.py
5. Open Control Panel, then navigate to Task Scheduler → Create → Scheduled task → User-defined script.
6. This leads to a Create task dialog, which you can fill in as follows:
   1. General:
      • Provide a task name, like User Backup Checker.
      • Select the admin account for UBC execution.
      • Select Enabled.
   2. Schedule:
      • Define the days, times, and frequency for executing UBC.
   3. Task Settings:
      • Choose Send run details by email and enter an email address if you wish to receive UBC reports by email.
        • Note: This setting only concerns admin emails. UBC directly sends emails to users with outdated backups.
        • Note: this setting requires an email account configured in Control Panel → Notification → Email.
      • Under Run command, write:

        python3 /volume1/homes/admin/user_backup_checker.py
        

        Adjust the path to match your setup.
7. Confirm with OK.

Done!

Configuration

Regular Settings

This section explains the settings that you can set in ubc/user_backup_checker.py. All settings are contained in the dict CONFIG. (user_backup_checker.py can be loaded as a module, which allows to set settings in an external script and leave the original file unchanged!)

The settings are:

• USERS_TO_EXCLUDE: Usernames that UBC shall not check, given as a Python set. You can mix local and domain users here, and UBC ensures that usernames are unique across both types.
• USER_DETECTION_LOOKUPS:
  • Nested dictionary structure specifying UBC's search patterns to detect users and their backup directories on the Synology server.
    • Outer dictionary level: Keys are the user types (e.g. local, domain) and values are the corresponding search patterns (see inner dictionary level).
    • Inner dictionary level: Inner dicts have two keys:
      1. "home_dirs_glob": Glob pattern that expands to the users' home folders. The last component of each matched path has to be the user name.
      2. "backup_subdir": Path to the Synology Drive backup folder relative to a user's home folder.
  • See here for naming and location of home directories of domain and LDAP users: https://kb.synology.com/en-us/DSM/help/DSM/AdminCenter/file_directory_service_user_group?version=7
• EXCLUDE_WEEKENDS: If True, Saturdays and Sundays are not counted towards the age of a backup. Moreover, if True, UBC sends no emails to individual users on these days either. This setting is useful, for example, if all users work Monday to Friday.
• TOLERANCE_FUTURE:
  • Number of days into the future in which UBC does not consider modification dates of files as future-dated yet. Setting this tolerance may be useful if users in different time zones perform backups.
• TOLERANCE_OUTDATED:
  • Maximum age of a backup to not be considered outdated yet.
• REMINDER_INTERVAL:
  • Interval (in days) at which UBC sends users a reminder email for their outdated backup. For example, a value of timedelta(days=1) means that users shall receive an email every single day after the age of their backup surpasses TOLERANCE_OUTDATED, or timedelta(days=3) means that they receive such an email only every three days. Emailing users daily may be counter-productive because they may start ignoring these emails. (This setting is only used when user notifications are enabled.)
• SUBJECT_OUTDATED:
  • Subject of an email to a user with an outdated backup. (This setting is only used when user notifications are enabled.)
• MAIL_OUTDATED:
  • Text of an email to a user with an outdated backup. This message needs to contain the strings {date} and {outdated_days}, which will be replaced for each user separately by the date and age of the last backup. (This setting is only used when user notifications are enabled.)
• SUBJECT_FUTURE:
  • Subject of an email to a user with a future-dated backup. (This setting is only used when user notifications are enabled.)
• MAIL_FUTURE:
  • Text of an email to a user with a future-dated backup. This message needs to contain the strings {path} and {date}, which will be replaced for each user separately by the path and date of the future-dated file. (This setting is only used when user notifications are enabled.)
• ADMIN_STATUS_REPORT:
  • Text of status report to server admins. This message needs to contain the strings {outdated_users}, {future_users}, and {ok_users}, which will be replaced by the usernames of the outdated, future-dated, and OK users.

Enabling User Notifications

UBC can periodically email users with outdated backups or future-dated files to notify them of the problem. However, there is no interface for third-party programs to send emails via the connection configured in Control Panel → Notification → Email. Therefore, you need to configure a separate email service so that UBC can send user notifications. Proceed as follows:

1. Create a subclass of MailClient that implements the methods get_email_address and send_email. For most Synology setups, this likely means connecting via SMTP to an existing email address, which UBC then uses to send the emails to individual users. The following Python modules may be of help:
   • smtplib
   • email
2. Call main() with an instance of your MailClient (sub-)class for the argument mail_client.

By doing so, UBC will enable the user notification feature and use the object you pass to send the emails.

Copyright

UBC is released under the GNU Affero General Public License v3.0

Copyright 2023, ETH Zurich.

Developer: Christian Zingg as employee at Chair of Systems Design, ETH Zurich.