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Backup and Restore ​

For compatibility with older links, this page still uses the /en/help/sync-and-backup path. However, the current product terminology no longer describes WebDAV as a standalone “sync” feature, so this page should be read as a backup-and-restore guide.

1. What this page now covers ​

  • WebDAV is mainly used to store local-library backups, manage restore points, and support migration or disaster recovery.
  • This page focuses on “backup, restore, and migration,” not “real-time consistency across devices.”
  • If older docs, screenshots, or previous versions still mention “Sync and Backup,” the current in-app wording “WebDAV Backup” takes precedence.

2. Backup prerequisites ​

For backup to succeed, the following usually need to be true:

  1. WebDAV is enabled and the server URL is reachable.
  2. The current account has a local library (only local libraries support backup / restore).
  3. Local-library backup is enabled.
  4. A backup password has been provided (required when backup is enabled; optionally remembered).

If any of the above is missing, the backup action may fail or remain disabled.

3. WebDAV connection recommendations ​

Under “Server Connection,” users typically configure:

  • Server URL
  • Username / Password
  • Auth Mode (Basic or Digest)
  • Root Path
  • Ignore TLS Errors (not recommended for long-term use)

Practical recommendations:

  • Prefer HTTPS and do not ignore TLS errors for long periods.
  • Use a dedicated Root Path to avoid mixing data with other apps.
  • URLs and paths are usually normalized on save (for example by trimming redundant slashes).

4. What a manual backup does ​

When “Start Backup” is triggered, the flow generally:

  1. Reads memos, archived content, and readable attachments from the current local library.
  2. Creates a snapshot and backup index.
  3. Encrypts the backup on the client side and uploads it to WebDAV.
  4. Updates the latest-backup time and snapshot records.

This means the backup source is the current local-library state, not a direct full-database copy of a remote service.

5. How automatic backup is triggered ​

Automatic backup is not a permanently running background poller. It is typically checked when the app returns to the foreground:

  • The backup schedule is not manual (that is, it is daily or weekly).
  • Enough time has elapsed since the last backup.
  • The backup password has been saved (automatic backup usually does not run without it).

If users want more stable automatic backup behavior, enabling “Remember Password” is recommended.

6. Retention and storage usage ​

The “Retention Count” setting controls how many snapshot versions are kept (minimum 1, default 5).
When the retention limit is exceeded, older snapshots are removed, and object storage is reclaimed according to reference usage so storage does not grow indefinitely.

In simple terms:

  • Higher retention means more restore points.
  • Higher retention usually also means more storage usage.

7. Restore flow and impact scope ​

When “Restore from Cloud” is triggered, the flow generally:

  1. Prompts for or reads the backup password.
  2. Lets the user choose a snapshot (typically showing time, memo count, file count, and size).
  3. Runs the restore after confirmation.

Restore typically has the following effects:

  • Current local-library files are overwritten.
  • Local attachment cache is cleared and restored according to the selected snapshot.
  • Local data state is rebuilt based on the selected snapshot.

Restore is therefore an overwrite operation, so the selected snapshot should be verified carefully before proceeding.

8. Security model ​

Backup data is not uploaded in plaintext:

  • AES-GCM-256 is used for encryption.
  • Password-derived keys use PBKDF2(HMAC-SHA256) (default 200000 rounds).
  • Keys for different purposes are separated via HKDF.
  • Both snapshots and indexes are stored in encrypted form.

9. Common failure causes ​

If backup or restore fails, check in this order:

  1. Whether the WebDAV URL is valid and reachable.
  2. Whether TLS / certificate issues exist (especially with self-signed setups).
  3. Whether the current account has a local library.
  4. Whether the backup password is correct.
  5. Whether recoverable snapshots actually exist in remote storage.
  1. Complete WebDAV connection setup.
  2. Enable local-library backup and set the password.
  3. Run one manual backup.
  4. Immediately perform a small restore drill.
  5. Then enable a daily or weekly schedule.