NG Backup

Encrypted, incremental backups of Nextcloud (database, configuration and data) with restore from the web interface. Works without shell access: no external programs, no extra PHP extensions beyond sodium for ng_backup itself. Runs on Nextcloud All-in-One, regular installations and hosted Nextcloud. (Choosing SMB as a storage backend is the one exception: see "Storage backend experiences" below — that requirement comes from files_external, not from ng_backup, and applies to any Nextcloud app that writes to an SMB share.)

Status: pre-release. Not yet tested on production. See PLAN.md for the design and docs/HOWTO.md for a step-by-step guide from setup to a tested restore.

License: AGPL-3.0-or-later.

How it works

• Backups go to a location: S3 (and S3-compatible storage), SFTP, WebDAV, FTP, Swift or a local path. NG Backup uses the connection code of Nextcloud's External storage app, but never mounts the location: it is only connected while a backup or restore runs, and it never appears in Files, for anyone.
• Data is cut into blocks, deduplicated, compressed and encrypted (XChaCha20-Poly1305) before it leaves the server, and streamed straight to the location: no local copy, no double disk space. Unchanged files are not read again; only new data is uploaded.
• The database is dumped through Nextcloud's own connection, inside one consistent transaction.
• Restores go through Nextcloud, so overwritten files keep their old content as a version and removed files go to the trash.

Quick start

occ backup:key:init --label="Safe"                 # first passphrase, deletion delay (default 7 days)
occ backup:key:slot:add --label="CTO"              # optional second and third passphrase
occ backup:key:slot:add --label="Head of IT"
occ backup:key:kit --output=/var/tmp/ng_backup-kit.json
occ backup:key:confirm
occ backup:target:add offsite amazons3 -a amazons3::accesskey -o bucket=... -o key=... -o secret=...
occ backup:run

Or use Administration settings → NG Backup.

The backup key, passphrases and the recovery kit

All backups of an installation are encrypted with one master key.

• The server keeps the master key, encrypted with the instance secret, so scheduled backups and restores work without anyone typing a passphrase. Any administrator can restore from the web interface. Consequence: whoever fully controls the server can read the backups; whoever only gets hold of the backup location cannot.

• For a restore on a new server (disaster recovery) you need the recovery kit and one passphrase. The kit contains the master key, encrypted separately with each passphrase.

• Up to three passphrases ("slots") can open the key, so one person leaving or dying does not lock the company out. A suggested setup:

  Slot	Kept by
  1	in the safe (sealed envelope)
  2	the CTO
  3	the head of IT

  Every holder keeps a copy of the same recovery kit and only knows their own passphrase. Using a single slot is possible, but then that one passphrase is a single point of failure.

• When a holder leaves, give their slot a new passphrase (occ backup:key:slot:replace), download the new kit and confirm it. Note: an old kit together with the old passphrase still opens the same master key; to revoke it completely, start new locations with a new key.

• Downloading the kit, and every change to the slots, requires the administrator's password, is written to the audit log and is announced to all administrators.

Protection against ransomware and a compromised server

A backup is only useful if an attacker cannot destroy it. An attacker with administrator access to Nextcloud could try to remove old restore points so that only infected data remains. NG Backup makes this hard and visible, but software alone can never guarantee it: the location must refuse deletions itself.

What NG Backup does:

• Deletion delay. Removed restore points first go to a trash on the location and are only deleted after the delay chosen at installation (default 7 days, cannot be changed afterwards). Within that time any administrator can bring them back (occ backup:trash:restore, or in the web interface).
• Notifications to all administrators when restore points are removed, the retention is changed, append-only is turned off, a location is removed or the recovery kit is downloaded, and an entry in the audit log (admin_audit).
• Append-only locations (occ backup:target:append-only NAME on): NG Backup never deletes anything there; old data is cleaned up by the location's own lifecycle rules.
• Removing a location in NG Backup only removes the connection. The backups on the location are not touched and nothing keeps cleaning up in the background.

What you should do on the location (strongly recommended):

• S3: enable Object Lock on the bucket, in compliance mode, with a default retention of for example 90 days, plus versioning. Then nobody, not even with the server's credentials, can delete or overwrite backups younger than 90 days. Combine with an append-only location in NG Backup and a lifecycle rule that removes old versions after the lock expires. With Object Lock, a deletion by NG Backup (or by an attacker through it) only adds a delete marker: the locked data stays and can be brought back from the bucket's object versions until the lock expires. Tested with an S3-compatible server; still to be verified on AWS itself, which requires a checksum on uploads to locked buckets.
• Use credentials without delete rights for the backup location where the storage supports it.
• SFTP / storage boxes: enable the provider's own snapshots (e.g. daily, kept 30-90 days) and give the backup user access to its own folder only, without a shell.
• Keep at least one location off-site, on a different network than the Nextcloud server.

Restore

• Files and folders of a user: in the web interface or occ backup:restore, into a new folder ("Restored "), merged into the original place, or replacing it.
• Raw restore of any path (for example config/) to a local directory: occ backup:restore ... --to-directory=DIR.
• Whole server (disaster recovery onto a fresh installation): occ backup:restore:full, see the how-to.
• One user (account, settings, files, calendars, contacts via user_migration): occ backup:user:backup and occ backup:user:restore, replacing the account or restoring it as <uid>-bak. See the how-to.

Storage backend experiences

Notes from actually running a backend, beyond what's in files_external's own documentation. Contributions welcome via PR — add what you ran into with your own provider.

• Hetzner Storage Box, sub-account: the SFTP backend's root option must be home, not /. A sub-account's SFTP login lands in /home (confirmed via pwd() after login); writing to the literal chroot root (/) fails with a generic NET_SFTP_STATUS_FAILURE from the SFTP server, while the same write under home (or a path below it) succeeds. This affects any backend option form that lets you set a path relative to the account's root, not just ng_backup. Not yet verified whether this also applies to a Hetzner Storage Box main account (only tested with a sub-account so far) — if you've tried a main account, please say so in a PR.

• FTP, server-dependent absolute-path handling: files_external's FTP backend always builds absolute paths (e.g. MKD /repo) for the configured root, never relative ones. atmoz/sftp-style vsftpd test servers (chrooted) can reject that with a generic "create directory operation failed", even though a plain ftp_mkdir() with a relative path on the same server succeeds; pure-ftpd accepts the absolute form fine. If a working FTP server rejects ng_backup's writes, try a different FTP server implementation before assuming the backend itself is broken.

• SMB/CIFS lists as available with just the smbclient CLI binary, but does not actually work for ng_backup without the smbclient PECL extension too. files_external falls back to a shell-wrapped smbclient process when the native extension is missing, which registers the backend in occ backup:target:backends fine, but that fallback's stream cannot seek. ng_backup reads blobs back by byte range while backing up, so even the very first (small) backup fails with Seek failed in packs/.... Install the extension (libsmbclient-dev + pecl install smbclient + docker-php-ext-enable smbclient on Debian-based images), not just the CLI tool — the backend being listed is not proof it will work here. Once the extension is present it works the same as any other backend; no ng_backup-specific config beyond host/share/user/password.

• NFS is not a files_external backend at all. Mount the NFS export on the server yourself (e.g. via /etc/fstab or a systemd .mount unit) and point ng_backup's local backend at the mount point; ng_backup never mounts or unmounts anything on its own, so an NFS mount dropping mid-run behaves like any other local-path failure (the run resumes). See PLAN.md 3.5 for why NFS can't be driven from PHP directly.

Commands

Command	Purpose
backup:key:init, backup:key:kit, backup:key:confirm	create the key, recovery kit, confirmation
backup:key:slots, backup:key:slot:add/replace/remove	passphrase slots
backup:target:backends/add/list/remove/append-only	backup locations
backup:run, backup:status, backup:list	back up, status, restore points
backup:browse, backup:restore	browse and restore
backup:retention, backup:prune, backup:trash, backup:trash:restore	retention, cleanup, trash
backup:verify	checksum audit of a restore point (--deep downloads and decrypts everything)
backup:restore:full	whole-server restore onto a fresh installation (after backup:key:import)
backup:key:import	import a recovery kit on a fresh installation
backup:user:backup, backup:user:restore	one user via user_migration (asks before installing it)