Add first draft of ZFS auto-snaptshot code

content/snippets/zfs-automatic-snapshots.md

@@ -0,0 +1,61 @@
+---
+title: "ZFS Automatic Snapshotting"
+date: 2022-10-31T17:56:35Z
+tags: ["archlinux", "linux", "zfs"]
+draft: true
+icon: backup
+---
+
+## Goal
+
+## Solution
+### Creating snapshots
+{{< codegroup >}}
+Systemd-timer
+```
+[Unit]
+Description=Create a daily ZFS snapshot for %I
+
+[Timer]
+OnCalendar=daily
+Persistent=true
+
+[Install]
+WantedBy=timers.target
+```
+Systemd-service
+```
+[Unit]
+Description=Create a ZFS snapshot for %I
+DefaultDependencies=no
+
+[Service]
+Type=oneshot
+RemainAfterExit=yes
+ExecStart=/usr/bin/bash -c '/usr/bin/zfs snapshot "%I@daily-$(date "+%%Y-%%m-%%d")"'
+```
+{{< /codegroup >}}
+
+### Cleaning up snapshots
+Get all older snapshots
+{{< codegroup >}}
+bash
+```
+zfs list -t snapshot -o name | \
+perl -e '
+my $one_week_ago = `date --date "7 days ago" "+%s"`;
+my %snapshots = ();
+
+for (<>) {
+    if (my ($dataset, $snapshot, $date) = /([\w\/]+)@(daily-(\d+\-\d+\-\d+))/) {
+        if (`date --date "$date" "+%s"` < $one_week_ago) {
+            push(@{$snapshots{$dataset}}, $snapshot);
+        }
+    }
+}
+
+while(my ($key, $value) = each %snapshots) {
+    print "$key@", join(",", @{$value}), "\n";
+}'
+```
+{{< /codegroup >}}