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| # Pruning | ||
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| Pruning is the process of removing backups that no longer are needed. | ||
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| mysql-backup does **not** do this by default; it is up to you to enable this feature, if you want it. | ||
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| ## Launching Pruning | ||
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| Pruning happens only in the following scenarios: | ||
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| * During pruning runs | ||
| * During backup runs | ||
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| It does not occur during restore runs. | ||
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| ### Pruning Runs | ||
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| You can start `mysql-backup` with the command `prune` to run a pruning operation. It will prune any backups that are no longer needed. | ||
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| Like backups, it can run once and then exit, or it can run on a schedule. | ||
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| It uses the same configuration options for scheduling as backups, see the [scheduling](./scheduling.md) documentation for more information, | ||
| specifically the section about [Scheduling Options](./scheduling.md#scheduling-options). | ||
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| ### Backup Runs | ||
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| When running `mysql-backup` in backup mode, it _optionally_ can also prune older backups before each backup run. | ||
| When enabled, it will prune any backups that fit the pruning criteria. | ||
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| ## Pruning Criteria | ||
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| Pruning can be on the basis of the _age_ of a specific backup, or the _number_ of backups. Both are set by the configuration setting: | ||
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| * Environment variable: `RETENTION=<value>` | ||
| * CLI flag: `dump --retention=<value>` or `prune --retention=<value>` | ||
| * Config file: | ||
| ```yaml | ||
| prune: | ||
| retention: <value> | ||
| ``` | ||
| The value of retention always is an integer followed by a letter. The letter can one of: | ||
| * `h` - hours, e.g. `2h` | ||
| * `d` - days, e.g. `3d` | ||
| * `w` - weeks, e.g. `4w` | ||
| * `m` - months, e.g. `3m` | ||
| * `y` - years, e.g. `5y` | ||
| * `c` - count, how many backup to keep, e.g. `10c`; this could have been simply `10`, but was kept as `c` to avoid accidental confusion with the other options. | ||
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| Most of these are interchangeable, e.g. `3d` is the same as `72h`, and `4w` is the same as `28d` is the same as `672h`. | ||
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| When calculating whether or not to prune, `mysql-backup` __always__ converts the amount to hours, and then errs on the side of caution. | ||
| For example, if provided `7d`, it will convert that to `168h`, and then prune any backups older than 168 full hours. If it is 167 hours and 59 minutes old, it | ||
| will not be pruned. | ||
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| ## Determining backup age | ||
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| Pruning depends on the name of the backup file, rather than the timestamp on the target filesystem, as the latter can be unreliable. | ||
| This means that the filename must be of a known pattern. | ||
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| As of this writing, pruning only work for backup files whose filename uses the default naming scheme, as described in | ||
| ["Dump File" in backup documentation](./backup.md#dump-file). We hope to support custom filenames in the future. |