Backups

What a backup is

A backup is a second copy of your files, kept where a single accident can’t reach it, that you have checked you can get back. Without that last part it’s only a hope.

Drives fail without warning, laptops get stolen, files get deleted by mistake, and ransomware (malicious software that scrambles your files and demands payment) encrypts everything it can reach. A good backup turns each of those from a disaster into an afternoon of restoring.

The 3-2-1 rule

This is the rule backup professionals use, and the one to aim for:

• 3 copies of anything you care about: the original and two backups.
• 2 separate devices or kinds of storage, so one fault can’t take every copy. Your computer’s drive and a USB hard drive count as two. So do a home server and a cloud storage service.
• 1 copy outside your home, so a fire, flood or burglary doesn’t take everything at once.

Here’s what that looks like for a household with a home server:

Two habits make it stronger. Keep one copy that ransomware can’t reach, either unplugged or in cloud storage set so that old versions can’t be deleted. And restore something now and then, because a backup you’ve never restored from is untested.

How backup software works

Modern backup tools all work in roughly the same way:

• Snapshots. Each run saves a snapshot, a record of what every file looked like at that moment, so you can go back to last night, last month or last year.
• Only changes are stored. After the first full copy, each run saves only what’s new or different, and identical pieces of files are stored once. This is called deduplication, and it’s why daily snapshots take little space.
• Encryption. Everything is scrambled with your password before it leaves the computer, so a cloud company can’t read it.
• Retention. A rule such as “keep 7 daily, 4 weekly and 12 monthly snapshots” clears out old ones automatically.
• Checks. The tool can read the backup back to make sure nothing in it is damaged.

What it needs

• Somewhere to back up to. A USB hard drive bigger than the data you’re protecting is the cheapest start. For the off-site copy, use a cloud storage service that charges by the gigabyte, or a second drive kept at someone else’s house.
• A password you won’t lose. Encrypted backups can’t be opened without it. Keep it in your password manager and on paper somewhere safe.
• A list of what matters. Usually documents, photos, and each app’s data folder on a server. Programs and operating systems can be reinstalled, so they matter less.
• An evening to set it up, and a reminder to test a restore every month or two.
• Patience with the first run. The first upload to cloud storage can take days on a slow connection. Later runs are much quicker.

How Restic fits in

Restic is the engine, and Backrest is the dashboard most people use with it.

• Encrypted. Every backup is encrypted with your repository password.
• Deduplicated snapshots, so nightly backups take little extra space.
• Almost any destination. A USB drive, another computer on your network, or cloud storage such as Backblaze B2 or any S3-compatible service (S3 is the storage format most cloud providers support).
• Checks itself. It can read back the stored data to confirm it’s intact.
• Runs everywhere. One small program for Linux, Windows and Mac, and a backup made on one can be restored on another.
• Backrest adds the web page: schedules, retention rules, a browser for old snapshots with a restore button, and notifications when a backup fails.

The easy way to set it up

The easiest route depends on what you’re backing up, and none of them needs the terminal.

• A Windows PC: Backrest has a normal Windows installer. It downloads Restic for you, and a small app by the clock keeps it running. Its web page is at http://localhost:9898.
• A home server running TrueNAS: Backrest is in the TrueNAS app catalogue.
• A home server running ZimaOS or CasaOS: Duplicati, from the options below, is in the App Store and does the same job from a web page, with encryption and many destinations. It’s a different program from Restic, and the one-click route on those systems.
• A Mac: Time Machine is built in and backs up to a USB drive or a network share once you choose the drive. For an encrypted copy in the cloud as well, Kopia’s desktop app, KopiaUI, has a normal Mac installer.

Then, in Backrest’s web page (Duplicati’s works much the same way):

1. Create a username and password when it asks.
2. Add a repository, Restic’s word for the place backups are stored: a folder on your USB drive, or your cloud storage account details. Set the repository password and save it in your password manager straight away.
3. Add a plan: the folders to back up, a schedule such as every night at 2 am, and how many snapshots to keep.
4. Run it once by hand and let the first backup finish.
5. Restore one file from the snapshot browser into a different folder, and open it.
6. Repeat with a second repository for the off-site copy, so you have both a local and an off-site backup.

The terminal route is Restic on its own, scheduled by the operating system, for people who prefer it.

Questions people ask

Isn’t iCloud or Dropbox already a backup?

Not on its own. They sync, so a deleted or scrambled file disappears from every device too. Some keep deleted files for a limited time, which helps, but a real backup keeps old versions for as long as you choose.

How much does the off-site copy cost?

Cloud storage of the kind Restic writes to is charged by the gigabyte each month, so the cost grows with your data. A drive at a relative’s house costs only the drive.

How do I back up apps like Immich or Jellyfin?

Back up each app’s data folder along with your files. Apps with a database need care, because copying a database while it’s being written can give you a broken copy. Stop the app during the backup, or back up the database copy the app makes itself, as Immich does every night.

How often should I test a restore?

Restore a file or two every month or two, and once a year try restoring a whole folder onto a different computer. The day you need the backup is the wrong day to find out it doesn’t work.

What if I forget the password?

Then nobody can open the backup, you included. That’s the price of encryption, so store the password in two places.