# ZFS Snapshot Checker

Script to check zfs snapshot counts and age of oldest most recent snapshot. Specifically, this script iterates over a number of specified datasets, determines for each the age of the most recent snapshot (with a specified prefix), and then computes the maximum of those ages. This can be used to monitor zfs snapshotting and replication tools such as [zrepl](https://zrepl.github.io), [sanoid/syncoid](https://github.com/jimsalterjrs/sanoid/wiki). In addition, the script determines the number of snapshots for each specified dataset, as well as the maximum of those numbers. This facilitates monitoring of proper snapshot pruning.


## Examples

```bash
# Basic check
./checkSnapshots.sh -d tank/data

# Recursive with verbose output
./checkSnapshots.sh -d tank/data -r -v

# Provide limits (max 20 snapshots, max age 24h), resulting exit code 1, if limits are exceeded.
./checkSnapshots.sh -d tank/data -s 20 -m 24h
```

## Options

```bash
-d, --dataset <dataset>         Dataset to check (required, repeat for multiple)
-e, --exclude <dataset>         Exclude dataset (repeat for multiple)
-p, --prefix <prefix>           Snapshot prefix (default: zrepl_)
-f, --format <format>           Timestamp format (see [below](#timestamp-formats--f))
-s, --max-snapshots <num>       Max snapshots per dataset
-m, --max-age <duration>        Max age (e.g., 31s, 17m, 24h)
-r, --recursive                 Include sub-datasets
-v, --verbose                   Show detailed table
-n, --err-for-no-snapshots      Error if no snapshots found
```

## Timestamp Formats (`-f`)

- `zrepl-dense` - `20060102_150405_000`
- `zrepl-human` - `2006-01-02_15:04:05`
- `iso-8601` - `2006-01-02T15:04:05Z`
- `unix-seconds` - Unix epoch
- `sanoid` - default sanoid format

Without this flag, ZFS creation time will be used.

## License

MIT License - see [LICENSE](LICENSE)