Déjà Dup
Simple backup tool for GNOME
Contents
Project Goals
Read our Mission Statement for full details, but basically we aim to convert people who don't currently have backups into people that do.
This may mean that we are too simple for some use cases. That's fine. We don't need to solve all backup needs.
Is Déjà Dup a System Backup?
Kind of, but not especially. It can back up system files for sure, but only ones your normal user can read. Which is a lot of them! But we are not a full system backup and don't aim to be. Déjà Dup is largely aimed at personal backups and doesn't work as well when run as root.
Running as root means that we can't integrate with your user session as well (notifications, keyring access, gamemode, gvfs mounts, etc). And we've chosen to focus on those kind of usability improvements.
There are other backup programs that aim to off full system backups as root, with a cron schedule, etc. Those are also great! If you need a multi-user or system backup, Déjà Dup may not be your best solution.
Duplicity
Déjà Dup is really just a clever graphical wrapper around the command line backup tool duplicity. You can read more about it on its homepage, but basically, it uses rsync to generate incremental, encrypted backup volumes.
Full Backups
Déjà Dup will occasionally make fresh full backups for you. This takes up more space and more time, but offers the following benefits:
- Full backups allow Déjà Dup to delete old backups. If it didn't create a new full checkpoint, it could never delete old full checkpoints and their chains of incremental backups.
- Sometimes there are bugs. Maybe somewhere in the Deja Dup app or Duplicity, or maybe you've got a flaky external disk. If all you had was a long chain of incremental backups and something goes wrong in the middle of the chain, you could invalidate months and months of backups down the chain. Now, bugs aren't expected, but better safe than sorry. The occasional full backup prevents hideously long chains of incremental backups, which would increase the risk.
Déjà Dup assumes that disk space is cheap, that time-to-backup isn't a terribly important detail, and that safety of data is paramount.
Deleting Old Backups
Déjà Dup lets you specify that you want backups to be kept for a period of time (say, six months), after which, you are OK with the backups being deleted. This does not mean that immediately after six months, Déjà Dup will delete all older backups. It's more complicated than that:
- Déjà Dup can only delete a complete chain of backups at a time. That is, a full backup and all its associated incremental backups.
- Déjà Dup still wants to keep two full backups around at all times (see above).
- There is a balance between making too many full backups (wasted time and space) and too few (backup chains become very long).
Assume that you have Déjà Dup setup to make a weekly backup and keep backups at least six months. By default, Déjà Dup will make a new full backup every three months. So, let's say you start January 1st:
- Jan 1st: Full Backup A
- Jan 8th: Incremental Backup A1
- ...
Apr 1st: Full Backup B (Won't delete backup chain A yet because we always keep two full backups)
- Apr 8th: Incremental Backup B1
- ...
Jul 1st: Full Backup C (Won't delete backup chain A yet because its oldest incremental backup is less than six months old and we can only delete a full chain at once)
- Jul 8th: Incremental Backup C1
- ...
Sep 30th: Incremental Backup C13 (After this, the last incremental backup in chain A is over six months old and we have more than two full backups, so chain A will be deleted)
(Those dates are a little fuzzy, since Déjà Dup actually works off days rather than months internally and its weekly backups wouldn't all fall on the 1st of each month anyway. But I'm just using the 1st of each month to make the logic easier to follow.)
Encryption
Déjà Dup relies on duplicity to handle the encryption, and it uses gpg with a symmetric cipher. Basically, that means it is encrypted just with the password your provide. You will need to remember that password to restore your data.
If you choose to have Déjà Dup remember your password, it will be stored in the default GNOME keyring.
Backup File Format
Déjà Dup uses an opaque format for files stored in your backup location. You must use Déjà Dup or another duplicity-based tool to restore your files. This is opposed to a native format where you can browse and examine your files using any normal file tool.
This naturally is a bummer. But it is necessary to support Déjà Dup's feature set:
- Encryption
- Compression
- Incremental backups
- Assuming little about location (allowing cloud backups)
- Supporting file permissions, even when backing up to locations that don't
Because of all the above, it is impossible to allow a version of your files that is accessible without duplicity. Note that there is a way to get your data back by hand, but it's not fun or easy.
Scheduling
Déjà Dup does not use cron or similar schedulers. Rather, it starts a program deja-dup-monitor when you log into your session. This keeps track of when you last successfully backed up and will wait until the next scheduled backup.
It determines exactly when the next scheduled backup is largely on its own, based on the user's preferences about whether to backup once a day, once a week, etc. There is no way to currently specify "as close to 4AM on Thursday as possible". See issue 111 for the related feature request.
Why Not Cron?
A monitoring program is used because access to the user session is useful for:
- prompting for passwords
- displaying status in the panel
- watching for events like plugging in a remote disk or becoming connected to the Internet
One disadvantage is that a backup can not be started while a user is not logged in. The primary use case for Déjà Dup is backing up user data, so this is not a large concern, as user data is unlikely to change while the user are not logged in.
Versioning
Déjà Dup follows the GNOME versioning scheme, but without following the GNOME release schedule.
Déjà Dup releases are not time based. Rather, the major number is incremented when a new release subjectively adds big enough features or changes features or dependencies in an important way.
For example after release 42.8, Déjà Dup was ported from GTK3 to GTK4. A big enough change for 43.alpha and 43.beta releases, then eventually a 43.0 stable release.
What's With the Name?
Déjà Dup is pronounced like day-ja-doop. It's a play on the French phrase "déjà vu" and "dup" from "duplication".
Once installed, it may show up as simply "Backups" in menus, app launchers, and some in-app text. This is to appear more tightly integrated into the system and to avoid confusion around the odd name.
But in app stores and formal contexts, we prefer the unambiguous "Déjà Dup Backups" to distinguish between multiple backup apps.
What Happened to the Files App Integration?
We used to ship a nautilus plugin that allowed restoring individual files by right clicking on the file or folder. But we took it out in version 42, largely for two reasons:
- A lot of users did not realize it even existed (they didn't expect that level of integration or just never looked for it).
Modern app delivery methods (snaps & flatpaks) use containers which don't allow us to integrate with the Files app at all.
So for our snap & flatpak releases, we needed to create an in-app file browse & restore interface to allow partial restores. And rather than maintain two different ways to restore files (one of which would only appear in certain releases of Déjà Dup which could confuse people), we dropped the old nautilus plugin in favor of the in-app browser.
If you want to restore files in versions 42 and above, switch to the Restore tab in the main interface, browse to the file you want and select it, then click Restore.
Cloud Backends
We aim to only focus on consumer-friendly cloud services. The full policy has more details, including which cloud services are deprecated.
Privacy
Read our privacy policy for full details, but basically, we don't collect any data.