walsnap

v0.3 · Go · source

Consistent backups for SQLite databases running in WAL mode.

cp db.sqlite backup.sqlite is fine right up until it isn't. In WAL mode the recent writes live in a separate log file, so the copy opens without complaint and contains the state of the last checkpoint, not the state of the last commit. Nobody notices until the day they have to restore.

walsnap takes the online backup, verifies the result with PRAGMA integrity_check, and can check that a chosen table still has recent rows. It exits non-zero on anything suspicious, so a cron job or a backup script notices.

Usage

walsnap backup app.db /backups/app-2026-09-14.db
walsnap backup --verify --recent messages:created_at app.db /backups/app.db
walsnap check /backups/app.db

Output is deliberately boring:

checkpoint: 412 pages
copied:     2.1 MiB
integrity:  ok
recent:     messages, newest 4m ago

Install

go install github.com/kuusela/walsnap@latest

Prebuilt Linux binaries for amd64 and arm64 are on the releases page.

Design notes

• Uses the online backup API, not file copying. A copy that races with a write is a copy that is wrong in a way you cannot see.
• Verification is on by default for backup. A backup you have not verified is a hope, not a backup.
• No configuration file. There are five flags and they fit on one line of --help.
• Exit codes are meaningful: 0 success, 1 usage, 2 source error, 3 verification failed.

Background

Written after a restore that lost a day of writes. The long version is in this post.