Initial version

README.md

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+# 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)