ZFS: dedup toggle per pool and dedup option for new datasets

Pool cards show the dedup ratio and can set dedup=on|off on the pool root
dataset (inherited by children); the new-dataset form gets a dedup option.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/zfsadm/zfsadm_test.go

@@ -31,6 +31,9 @@ func TestValidators(t *testing.T) {
 	if ValidateCompression("gzip") == nil || ValidateCompression("lz4") != nil || ValidateCompression("") != nil {
 		t.Error("compression validation")
 	}
+	if ValidateDedup("verify") == nil || ValidateDedup("on") != nil || ValidateDedup("") != nil {
+		t.Error("dedup validation")
+	}
 	if ValidateOwner("ansible") == nil || ValidateOwner("1000:1000") != nil || ValidateOwner("") != nil {
 		t.Error("owner validation")
 	}
@@ -74,6 +77,16 @@ func TestCreate(t *testing.T) {
 		t.Errorf("calls:\n%s\nwant:\n%s", strings.Join(f.calls, "\n"), strings.Join(want, "\n"))
 	}
 
+	// dedup goes between compression and quota
+	f = &fake{}
+	a = New(f.run)
+	if err := a.Create("tank/d", CreateOpts{Compression: "zstd", Dedup: "on", Quota: "1T"}); err != nil {
+		t.Fatal(err)
+	}
+	if len(f.calls) != 1 || f.calls[0] != "zfs create -p -o compression=zstd -o dedup=on -o quota=1T tank/d" {
+		t.Errorf("calls = %v", f.calls)
+	}
+
 	// no owner, inherit everything
 	f = &fake{}
 	a = New(f.run)
@@ -115,6 +128,28 @@ func TestCreate(t *testing.T) {
 	}
 }
 
+func TestSetDedup(t *testing.T) {
+	f := &fake{}
+	a := New(f.run)
+	for _, c := range [][2]string{{"tank/x", "on"}, {"tank", "verify"}, {"tank", ""}, {"-tank", "on"}, {"", "off"}} {
+		if err := a.SetDedup(c[0], c[1]); err == nil {
+			t.Errorf("%q=%q accepted", c[0], c[1])
+		}
+	}
+	if len(f.calls) != 0 {
+		t.Errorf("rejected input ran commands: %v", f.calls)
+	}
+	if err := a.SetDedup("tank", "on"); err != nil {
+		t.Fatal(err)
+	}
+	if err := a.SetDedup("tank", "off"); err != nil {
+		t.Fatal(err)
+	}
+	if strings.Join(f.calls, "|") != "zfs set dedup=on tank|zfs set dedup=off tank" {
+		t.Errorf("calls = %v", f.calls)
+	}
+}
+
 func TestDestroyEmpty(t *testing.T) {
 	ok := map[string]string{"zfs list -Hp -r -t filesystem": "tank/x\t98304", "zfs list -H -t snapshot": ""}
 	f := &fake{reply: ok}