Hosting a Backup

This is the other half of backup, where your device keeps someone else's. You create a vault, cap its size and hand over an invitation, and from then on their device deposits encrypted snapshots into it on its own schedule. You can never read what is inside, and hosting costs nothing, with or without Pro.

Creating a vault

On the Content tab, choose New backup target… and give it a name, usually the name of the person, such as "Anna". Set the storage cap and pick where the vault lives, either in internal storage or in a folder on an external drive. Use a drive when you can, as the backup of someone else is usually far bigger than the internal storage of an old phone. Vaults are listed in their own section of the content list, apart from your own folders.

The invitation

Share Invitation produces a short message carrying everything the other device needs, which is the address, the access key of the vault and the cap. Sent with Mail it carries a subject line. The link inside opens a page explaining the app to someone who does not have it yet, and on a device with NAS Reborn installed it opens in the app, ready to add. The credentials ride in a part of the link that never travels in a web request.

The invitation cannot read the backup, but anyone holding it can delete it or fill the space, so you should share it over a private channel such as AirDrop or Messages.

One vault belongs to one device. The first device to back up claims it and a second one is refused with a message saying so. To host another person, create another vault.

What you can and cannot see

The screen of the vault shows how much is stored against the cap and when the guest last backed up, and that is all it can show. The objects inside are sealed with keys your device has never seen, so there are no file names, no folder structure and no readable content, not in the app, not on the network drive and not over S3. What you can see as a host is the rough total size, the number of objects and when uploads happen. Beside the sealed objects the vault folder holds a plain-text README and the small script the guest would use to restore without the app, neither of which can read anything on its own.

Caps, pausing and eviction

Uploads past the cap are refused with a message telling the guest to ask you for more room, and raising the cap is one field on the screen of the vault. Pause refuses the key of the guest until you resume, which is useful when the vault sits on a drive you need to unplug. Evict Vault deletes the data of the guest from your device and revokes their key. This cannot be undone here, but the guest keeps their originals and only needs a new home for their backup.

Hosting is free

A vault does not count against the folder or storage limits, so a friend can install the app and keep your backup without buying anything. Backing up your own server is the other side of this, see Backing Up Your Server.

Being reachable

The device of the guest can only deposit backups while yours is serving, so keep the app in front as described in Always-On Serving, or simply running when the host is a Mac. An invitation created while the device only has its local-network name works on your own network alone, so switch the Serve tab to Internet first when the guest lives further away, and see Reachability for what that involves. A backup that cannot reach your device is not lost. It waits and tells its owner that it is falling behind.