nextcloud-ng_backup/docs/DISASTER-RECOVERY.md

Disaster recovery: your server is gone

Your Nextcloud server is lost. You have a new, empty server. These are the steps to get your Nextcloud back from an NG Backup location. Do them in this order.

What you need

• The recovery kit file (ng_backup-kit.json) and one passphrase of it.
• The connection details of the backup location: host, user, password or keys, bucket, folder.
• A new server with the same Nextcloud major version as the old one (for example 34), a database (PostgreSQL, MySQL/MariaDB or SQLite; it may differ from the old one) and room for the whole backup plus a margin.
• Shell access to the new server, to run occ (on a hosted Nextcloud without it, your provider runs these steps).
• A list of the apps that are not in the app store (your own builds, apps copied in by hand). Keep their packages somewhere safe beforehand.

No kit? If the location still holds its config file, the key is there too, but this version can only import it from a kit. Keep the kit off the server, next to the passphrase.

Steps

1. Install a fresh Nextcloud of the same major version. Create an admin account. Do not add users or files.

2. Do not let background jobs run yet. A new Nextcloud runs them on page visits (AJAX). Switch that off:

occ background:cron

As long as no cron is set up, nothing runs. Check that none is:

• Regular server: sudo crontab -u www-data -l. If it shows a line with cron.php, remove it for now with sudo crontab -u www-data -e (put it back in step 9).
• Docker Compose with a cron service: docker compose stop cron.
• Nextcloud All-in-One: cron runs inside the Nextcloud container; leave it. It does no harm here: the restore keeps NG Backup's own settings of the new server, so it does not start backups.

This keeps the new server quiet (no mail syncs, no notifications, no backups) until it is ready.

3. Install NG Backup (the same version or newer) and enable it.

4. Import the backup key. Copy the kit to the new server so the web server user can read it.

From your own computer:

scp ng_backup-kit.json root@newserver:/tmp/

Then on the server, one of:

chown www-data /tmp/ng_backup-kit.json                                    # regular server
docker cp /tmp/ng_backup-kit.json <container>:/tmp/ && \
  docker exec <container> chown www-data /tmp/ng_backup-kit.json          # Docker

<container> is the name of your Nextcloud container: docker ps shows it (for example nextcloud-aio-nextcloud, or myproject-nextcloud-1 with Docker Compose).

Import it; you type the passphrase yourself:

occ backup:key:import /tmp/ng_backup-kit.json

It shows the key fingerprint: it must match the one of your old server (on the recovery kit).

5. Add the backup location with the same details as before. On a large backup this first reads the index and shows how far it is, for example Reading the index: 6,913/26,791 files (25%), about 12 min left.

occ backup:target:add offsite sftp -a password::password -o host=... -o user=... -o password=... -o root=... --path=...

If it says "No backup key yet", the key is not imported. Run step 4:

occ backup:key:import /tmp/ng_backup-kit.json

Do not run backup:key:init, even though the message suggests it: that makes a brand new key, and your backups were encrypted with the old one. NG Backup then refuses the location ("created with a different key").

6. List the restore points and pick one, normally the newest:

occ backup:list offsite

7. Start the restore, and let it install the apps.

occ backup:restore:full offsite <snapshot> --install-apps

--install-apps first installs every app the old server had enabled from the app store (or switches it on, if it is part of Nextcloud). Tables of apps that are missing or were removed long ago are created from the backup, so they do not stop the restore.

At the end it lists the apps it could not install, usually your own builds that are not in the app store. Copy those into custom_apps and enable them (occ app:enable <app>); their data is already restored.

Backups made before 1.0.0-rc.2 do not record the structure of their tables. If the restore lists tables that do not exist here, install the apps they belong to and run it again, or leave them out with --skip-missing-tables.

8. Let the restore run. It restores the database, then the data directory, and takes hours for a large backup. Nextcloud is in maintenance mode meanwhile, so nobody and no background job writes into it; the restore switches it off when it completes. (If you had switched maintenance mode on yourself before, it stays on: switch it off with occ maintenance:mode --off when ready.)

If it stops halfway, maintenance mode stays on (the instance may be partly restored). Fix the cause, then switch maintenance mode off and run the restore again with --force, in one line (the message prints it): occ maintenance:mode --off && occ backup:restore:full <location> <snapshot> --force. It goes on where it stopped: data files that are already in place with the size and modification time of the backup are left, so only the rest comes from the location again (since 1.0.2; before, it started over). The database is restored again in full, which takes minutes. Leave out --install-apps this time, so that the instance is open only for the seconds until the restore has switched maintenance mode on again; apps the first run could not install are listed at the end of the restore, install those afterwards. If occ then says that Nextcloud or one of the apps requires an upgrade, the database is already the old server's: run occ upgrade first, then the same command with --force.

If the backup itself is damaged (the restore stops with "Decryption failed", "Blob verification failed" or a file that is missing on the location), try an older restore point first. If none is better, --salvage restores whatever can be read:

occ backup:restore:full offsite <snapshot> --install-apps --salvage

• Files that cannot be read are left out and listed at the end; everything else is restored.
• If the database cannot be restored (its dump is damaged, or it does not fit this installation), the database stays as the fresh installation made it, and the data directory and config of the backup go to a folder of their own in the data directory, ngb-salvage-<snapshot>. Each user's files are in data/<user>/files there: create the users again and copy their files back by hand (then occ files:scan --all). Calendars, contacts and shares are in the database and cannot be recovered this way.

The command then ends with exit code 2 instead of 0. The same option exists for occ backup:restore, to restore single folders.

9. After the restore. These worked in our tests:

occ upgrade
occ maintenance:repair
occ files:scan --all

• Check config/config.php: trusted_domains, overwrite.cli.url and overwritehost come from the old server; change them if the new server has another name. The database settings and the data directory are kept from the new installation.
• From Nextcloud All-in-One to a regular server: also check the cache settings (memcache.*, redis), which point at AIO's containers.
• Log in, open a few files, a calendar and a contact.
• Start background jobs again (cron), as in step 2 in reverse.

10. Point your domain at the new server and check that clients reconnect.

11. Make a backup of the new server to the same location (occ backup:run offsite). The old server must stay off: two servers must never write to the same location.

Never

• Never let the old server write to the location again if it comes back. Switch its backups off first.
• Never give your passphrase to anyone. Nobody helping you needs it.

Help

Stuck? Ensembia, the developer of NG Backup, offers paid help with restoring a backup after a crash.