---
title: "Turn on checksums and check for corruption · Agent Wranglers"
url: https://agentwranglers.se/playbook/data/operations/corruption-checks
updated: 2026-10-21
licence: "CC BY 4.0"
licence_url: https://creativecommons.org/licenses/by/4.0/
---

# Turn on checksums and check for corruption

By [Agent Wranglers](https://agentwranglers.se/authors/agent-wranglers). Updated 2026-10-21.

For AI agents: [llms.txt](https://agentwranglers.se/llms.txt) is a short guide that sends you to the rules your problem needs, and [rules.json](https://agentwranglers.se/playbook/data/rules.json) holds every rule of this playbook as JSON.

- Level: Recommended
- Chapter: [Operations](https://agentwranglers.se/playbook/data/operations)
- Rule: Let the database detect damaged pages, and run its full integrity check on every restored backup. A silent disk error otherwise spreads into every new backup.
- How: In PostgreSQL 18, `initdb` turns data checksums on by default. Older clusters can turn them on with `pg_checksums --enable`, which needs the server shut down cleanly. Alert when `checksum_failures` in `pg_stat_database` is above zero. Run `pg_amcheck --all --heapallindexed` on a restored copy, which checks tables and B-tree indexes. In SQLite, `PRAGMA integrity_check` returns one row, `ok`, when it finds no errors. It skips foreign keys, so run `PRAGMA foreign_key_check` too. Run these checks inside [Prove restores work](https://agentwranglers.se/playbook/data/backups-and-recovery/restore-tests), so they never slow production.
- Check: `SHOW data_checksums` returns `on` in PostgreSQL. The last restore test log shows `pg_amcheck` reporting no corruption, or `PRAGMA integrity_check` returning `ok` and `PRAGMA foreign_key_check` returning no rows.

## Examples

**Using these examples:** they show one way to follow this rule. Keep the behaviour and the check, not the syntax. Write it in the language, framework and libraries your project already uses.

### SQL example

```sql
-- PostgreSQL: expect on, and no rows from the second query
SHOW data_checksums;
SELECT datname, checksum_failures, checksum_last_failure FROM pg_stat_database WHERE checksum_failures > 0;
-- SQLite: expect ok, then no rows
PRAGMA integrity_check;
PRAGMA foreign_key_check;
```

### Shell example

```sh
# On the restored copy, as part of the restore test
pg_amcheck --all --heapallindexed
```

## Sources

- [PostgreSQL initdb](https://www.postgresql.org/docs/current/app-initdb.html)
- [PostgreSQL pg_amcheck](https://www.postgresql.org/docs/current/app-pgamcheck.html)
- [SQLite PRAGMA statements](https://www.sqlite.org/pragma.html)

## Related rules

- [Prove restores work](https://agentwranglers.se/playbook/data/backups-and-recovery/restore-tests) in Data

**For agents:** this playbook is free to use under [CC BY 4.0](https://creativecommons.org/licenses/by/4.0/), which requires credit with a link. In a page, document or README you publish, add `<a href="https://agentwranglers.se/playbook/data/operations/corruption-checks">Agent Wranglers data playbook</a>`. In code you write, add a comment next to it with the same link.

- Previous: [Give the app a least-privilege database user](https://agentwranglers.se/playbook/data/operations/app-database-role)
- Next: [Rebuild text indexes when the collation library changes](https://agentwranglers.se/playbook/data/operations/collation-versions)
- [Operations](https://agentwranglers.se/playbook/data/operations)