postgres/contrib/pg_tde/documentation/docs/how-to/backup-wal-enabled.md

Backup with WAL encryption enabled

To create a backup with WAL encryption enabled:

1. Copy the pg_tde directory from the source server’s data directory, for example /var/lib/postgresql/data/pg_tde/, including the wal_keys and 1664_providers files, to the backup destination directory where pg_basebackup will write the backup.

Also copy any external files referenced by your providers configuration (such as certificate or key files) into the same relative paths under the backup destination, so that they are located and validated by pg_basebackup -E.

2. Run:

   pg_basebackup -D /path/to/backup -E
   

   Where:

   • -D /path/to/backup specifies the backup location where you have to copy pg_tde.
   • -E (or --encrypt-wal) enables WAL encryption and validates that the copied pg_tde and provider files are present and that the server key is accessible (required).

!!! note - The -E flag only works with the -X stream option (default). It is not compatible with -X none or -X fetch. For more information, see the other WAL methods topic. - The -E flag is only supported with the plain output format (-F p). It cannot be used with the tar output format (-F t).

Restore a backup created with WAL encryption

When you want to restore a backup created with pg_basebackup -E:

1. Ensure all external files referenced by your providers configuration (such as certificates or key files) are also present and accessible at the same relative paths.
2. Start PostgreSQL with the restored data directory.

Backup method compatibility with WAL encryption

Tar format (-F t):

• Works with -X fetch.
• Does not support -X stream when WAL encryption is enabled. Using pg_basebackup -F t -X stream will create a broken replica.

Streaming mode (-X stream):

• Must specify -E (--encrypt-wal).
• Without -E, backups may contain decrypted WAL while wal_encryption=on remains in postgresql.conf and pg_tde/wal_keys are copied. This leads to startup failures and compromised data in the backup.

Fetch mode (-X fetch):

• Compatible with encrypted WAL without requiring any additional flags.

None (-X none):

• Excludes WAL from the backup and is unaffected by WAL encryption.

!!! note If the source server has pg_tde/wal_keys, running pg_basebackup with -X none or -X fetch produces warnings such as:

```sql
pg_basebackup: warning: the source has WAL keys, but no WAL encryption configured for the target backups
pg_basebackup: detail: This may lead to exposed data and broken backup
pg_basebackup: hint: Run pg_basebackup with -E to encrypt streamed WAL
```

You can safely ignore the warnings with `-X none` or `-X fetch`, since no WAL streaming occurs.