1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
|
.\"
.\" CDDL HEADER START
.\"
.\" The contents of this file are subject to the terms of the
.\" Common Development and Distribution License (the "License").
.\" You may not use this file except in compliance with the License.
.\"
.\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
.\" or http://www.opensolaris.org/os/licensing.
.\" See the License for the specific language governing permissions
.\" and limitations under the License.
.\"
.\" When distributing Covered Code, include this CDDL HEADER in each
.\" file and include the License file at usr/src/OPENSOLARIS.LICENSE.
.\" If applicable, add the following below this CDDL HEADER, with the
.\" fields enclosed by brackets "[]" replaced with your own identifying
.\" information: Portions Copyright [yyyy] [name of copyright owner]
.\"
.\" CDDL HEADER END
.\"
.\"
.\" Copyright (c) 2009 Sun Microsystems, Inc. All Rights Reserved.
.\" Copyright 2011 Joshua M. Clulow <josh@sysmgr.org>
.\" Copyright (c) 2011, 2019 by Delphix. All rights reserved.
.\" Copyright (c) 2011, Pawel Jakub Dawidek <pjd@FreeBSD.org>
.\" Copyright (c) 2012, Glen Barber <gjb@FreeBSD.org>
.\" Copyright (c) 2012, Bryan Drewery <bdrewery@FreeBSD.org>
.\" Copyright (c) 2013, Steven Hartland <smh@FreeBSD.org>
.\" Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
.\" Copyright (c) 2014, Joyent, Inc. All rights reserved.
.\" Copyright (c) 2014 by Adam Stevko. All rights reserved.
.\" Copyright (c) 2014 Integros [integros.com]
.\" Copyright (c) 2016 Nexenta Systems, Inc. All Rights Reserved.
.\" Copyright (c) 2014, Xin LI <delphij@FreeBSD.org>
.\" Copyright (c) 2014-2015, The FreeBSD Foundation, All Rights Reserved.
.\" Copyright 2019 Richard Laager. All rights reserved.
.\" Copyright 2018 Nexenta Systems, Inc.
.\" Copyright 2019 Joyent, Inc.
.\" Copyright (c) 2019, Kjeld Schouten-Lebbing
.\"
.Dd September 1, 2020
.Dt ZFSPROPS 8
.Os
.Sh NAME
.Nm zfsprops
.Nd Native properties and user-defined of ZFS datasets.
.Sh DESCRIPTION
Properties are divided into two types, native properties and user-defined
.Po or
.Qq user
.Pc
properties.
Native properties either export internal statistics or control ZFS behavior.
In addition, native properties are either editable or read-only.
User properties have no effect on ZFS behavior, but you can use them to annotate
datasets in a way that is meaningful in your environment.
For more information about user properties, see the
.Sx User Properties
section, below.
.Ss Native Properties
Every dataset has a set of properties that export statistics about the dataset
as well as control various behaviors.
Properties are inherited from the parent unless overridden by the child.
Some properties apply only to certain types of datasets
.Pq file systems, volumes, or snapshots .
.Pp
The values of numeric properties can be specified using human-readable suffixes
.Po for example,
.Sy k ,
.Sy KB ,
.Sy M ,
.Sy Gb ,
and so forth, up to
.Sy Z
for zettabyte
.Pc .
The following are all valid
.Pq and equal
specifications:
.Li 1536M, 1.5g, 1.50GB .
.Pp
The values of non-numeric properties are case sensitive and must be lowercase,
except for
.Sy mountpoint ,
.Sy sharenfs ,
and
.Sy sharesmb .
.Pp
The following native properties consist of read-only statistics about the
dataset.
These properties can be neither set, nor inherited.
Native properties apply to all dataset types unless otherwise noted.
.Bl -tag -width "usedbyrefreservation"
.It Sy available
The amount of space available to the dataset and all its children, assuming that
there is no other activity in the pool.
Because space is shared within a pool, availability can be limited by any number
of factors, including physical pool size, quotas, reservations, or other
datasets within the pool.
.Pp
This property can also be referred to by its shortened column name,
.Sy avail .
.It Sy compressratio
For non-snapshots, the compression ratio achieved for the
.Sy used
space of this dataset, expressed as a multiplier.
The
.Sy used
property includes descendant datasets, and, for clones, does not include the
space shared with the origin snapshot.
For snapshots, the
.Sy compressratio
is the same as the
.Sy refcompressratio
property.
Compression can be turned on by running:
.Nm zfs Cm set Sy compression Ns = Ns Sy on Ar dataset .
The default value is
.Sy off .
.It Sy createtxg
The transaction group (txg) in which the dataset was created. Bookmarks have
the same
.Sy createtxg
as the snapshot they are initially tied to. This property is suitable for
ordering a list of snapshots, e.g. for incremental send and receive.
.It Sy creation
The time this dataset was created.
.It Sy clones
For snapshots, this property is a comma-separated list of filesystems or volumes
which are clones of this snapshot.
The clones'
.Sy origin
property is this snapshot.
If the
.Sy clones
property is not empty, then this snapshot can not be destroyed
.Po even with the
.Fl r
or
.Fl f
options
.Pc .
The roles of origin and clone can be swapped by promoting the clone with the
.Nm zfs Cm promote
command.
.It Sy defer_destroy
This property is
.Sy on
if the snapshot has been marked for deferred destroy by using the
.Nm zfs Cm destroy Fl d
command.
Otherwise, the property is
.Sy off .
.It Sy encryptionroot
For encrypted datasets, indicates where the dataset is currently inheriting its
encryption key from. Loading or unloading a key for the
.Sy encryptionroot
will implicitly load / unload the key for any inheriting datasets (see
.Nm zfs Cm load-key
and
.Nm zfs Cm unload-key
for details).
Clones will always share an
encryption key with their origin. See the
.Em Encryption
section of
.Xr zfs-load-key 8
for details.
.It Sy filesystem_count
The total number of filesystems and volumes that exist under this location in
the dataset tree.
This value is only available when a
.Sy filesystem_limit
has been set somewhere in the tree under which the dataset resides.
.It Sy keystatus
Indicates if an encryption key is currently loaded into ZFS. The possible
values are
.Sy none ,
.Sy available ,
and
.Sy unavailable .
See
.Nm zfs Cm load-key
and
.Nm zfs Cm unload-key .
.It Sy guid
The 64 bit GUID of this dataset or bookmark which does not change over its
entire lifetime. When a snapshot is sent to another pool, the received
snapshot has the same GUID. Thus, the
.Sy guid
is suitable to identify a snapshot across pools.
.It Sy logicalreferenced
The amount of space that is
.Qq logically
accessible by this dataset.
See the
.Sy referenced
property.
The logical space ignores the effect of the
.Sy compression
and
.Sy copies
properties, giving a quantity closer to the amount of data that applications
see.
However, it does include space consumed by metadata.
.Pp
This property can also be referred to by its shortened column name,
.Sy lrefer .
.It Sy logicalused
The amount of space that is
.Qq logically
consumed by this dataset and all its descendents.
See the
.Sy used
property.
The logical space ignores the effect of the
.Sy compression
and
.Sy copies
properties, giving a quantity closer to the amount of data that applications
see.
However, it does include space consumed by metadata.
.Pp
This property can also be referred to by its shortened column name,
.Sy lused .
.It Sy mounted
For file systems, indicates whether the file system is currently mounted.
This property can be either
.Sy yes
or
.Sy no .
.It Sy objsetid
A unique identifier for this dataset within the pool. Unlike the dataset's
.Sy guid
, the
.Sy objsetid
of a dataset is not transferred to other pools when the snapshot is copied
with a send/receive operation.
The
.Sy objsetid
can be reused (for a new dataset) after the dataset is deleted.
.It Sy origin
For cloned file systems or volumes, the snapshot from which the clone was
created.
See also the
.Sy clones
property.
.It Sy receive_resume_token
For filesystems or volumes which have saved partially-completed state from
.Sy zfs receive -s ,
this opaque token can be provided to
.Sy zfs send -t
to resume and complete the
.Sy zfs receive .
.It Sy redact_snaps
For bookmarks, this is the list of snapshot guids the bookmark contains a redaction
list for.
For snapshots, this is the list of snapshot guids the snapshot is redacted with
respect to.
.It Sy referenced
The amount of data that is accessible by this dataset, which may or may not be
shared with other datasets in the pool.
When a snapshot or clone is created, it initially references the same amount of
space as the file system or snapshot it was created from, since its contents are
identical.
.Pp
This property can also be referred to by its shortened column name,
.Sy refer .
.It Sy refcompressratio
The compression ratio achieved for the
.Sy referenced
space of this dataset, expressed as a multiplier.
See also the
.Sy compressratio
property.
.It Sy snapshot_count
The total number of snapshots that exist under this location in the dataset
tree.
This value is only available when a
.Sy snapshot_limit
has been set somewhere in the tree under which the dataset resides.
.It Sy type
The type of dataset:
.Sy filesystem ,
.Sy volume ,
.Sy snapshot ,
or
.Sy bookmark .
.It Sy used
The amount of space consumed by this dataset and all its descendents.
This is the value that is checked against this dataset's quota and reservation.
The space used does not include this dataset's reservation, but does take into
account the reservations of any descendent datasets.
The amount of space that a dataset consumes from its parent, as well as the
amount of space that is freed if this dataset is recursively destroyed, is the
greater of its space used and its reservation.
.Pp
The used space of a snapshot
.Po see the
.Em Snapshots
section of
.Xr zfsconcepts 8
.Pc
is space that is referenced exclusively by this snapshot.
If this snapshot is destroyed, the amount of
.Sy used
space will be freed.
Space that is shared by multiple snapshots isn't accounted for in this metric.
When a snapshot is destroyed, space that was previously shared with this
snapshot can become unique to snapshots adjacent to it, thus changing the used
space of those snapshots.
The used space of the latest snapshot can also be affected by changes in the
file system.
Note that the
.Sy used
space of a snapshot is a subset of the
.Sy written
space of the snapshot.
.Pp
The amount of space used, available, or referenced does not take into account
pending changes.
Pending changes are generally accounted for within a few seconds.
Committing a change to a disk using
.Xr fsync 2
or
.Dv O_SYNC
does not necessarily guarantee that the space usage information is updated
immediately.
.It Sy usedby*
The
.Sy usedby*
properties decompose the
.Sy used
properties into the various reasons that space is used.
Specifically,
.Sy used No =
.Sy usedbychildren No +
.Sy usedbydataset No +
.Sy usedbyrefreservation No +
.Sy usedbysnapshots .
These properties are only available for datasets created on
.Nm zpool
.Qo version 13 Qc
pools.
.It Sy usedbychildren
The amount of space used by children of this dataset, which would be freed if
all the dataset's children were destroyed.
.It Sy usedbydataset
The amount of space used by this dataset itself, which would be freed if the
dataset were destroyed
.Po after first removing any
.Sy refreservation
and destroying any necessary snapshots or descendents
.Pc .
.It Sy usedbyrefreservation
The amount of space used by a
.Sy refreservation
set on this dataset, which would be freed if the
.Sy refreservation
was removed.
.It Sy usedbysnapshots
The amount of space consumed by snapshots of this dataset.
In particular, it is the amount of space that would be freed if all of this
dataset's snapshots were destroyed.
Note that this is not simply the sum of the snapshots'
.Sy used
properties because space can be shared by multiple snapshots.
.It Sy userused Ns @ Ns Em user
The amount of space consumed by the specified user in this dataset.
Space is charged to the owner of each file, as displayed by
.Nm ls Fl l .
The amount of space charged is displayed by
.Nm du
and
.Nm ls Fl s .
See the
.Nm zfs Cm userspace
subcommand for more information.
.Pp
Unprivileged users can access only their own space usage.
The root user, or a user who has been granted the
.Sy userused
privilege with
.Nm zfs Cm allow ,
can access everyone's usage.
.Pp
The
.Sy userused Ns @ Ns Em ...
properties are not displayed by
.Nm zfs Cm get Sy all .
The user's name must be appended after the @ symbol, using one of the following
forms:
.Bl -bullet -width ""
.It
.Em POSIX name
.Po for example,
.Sy joe
.Pc
.It
.Em POSIX numeric ID
.Po for example,
.Sy 789
.Pc
.It
.Em SID name
.Po for example,
.Sy joe.smith@mydomain
.Pc
.It
.Em SID numeric ID
.Po for example,
.Sy S-1-123-456-789
.Pc
.El
.Pp
Files created on Linux always have POSIX owners.
.It Sy userobjused Ns @ Ns Em user
The
.Sy userobjused
property is similar to
.Sy userused
but instead it counts the number of objects consumed by a user. This property
counts all objects allocated on behalf of the user, it may differ from the
results of system tools such as
.Nm df Fl i .
.Pp
When the property
.Sy xattr=on
is set on a file system additional objects will be created per-file to store
extended attributes. These additional objects are reflected in the
.Sy userobjused
value and are counted against the user's
.Sy userobjquota .
When a file system is configured to use
.Sy xattr=sa
no additional internal objects are normally required.
.It Sy userrefs
This property is set to the number of user holds on this snapshot.
User holds are set by using the
.Nm zfs Cm hold
command.
.It Sy groupused Ns @ Ns Em group
The amount of space consumed by the specified group in this dataset.
Space is charged to the group of each file, as displayed by
.Nm ls Fl l .
See the
.Sy userused Ns @ Ns Em user
property for more information.
.Pp
Unprivileged users can only access their own groups' space usage.
The root user, or a user who has been granted the
.Sy groupused
privilege with
.Nm zfs Cm allow ,
can access all groups' usage.
.It Sy groupobjused Ns @ Ns Em group
The number of objects consumed by the specified group in this dataset.
Multiple objects may be charged to the group for each file when extended
attributes are in use. See the
.Sy userobjused Ns @ Ns Em user
property for more information.
.Pp
Unprivileged users can only access their own groups' space usage.
The root user, or a user who has been granted the
.Sy groupobjused
privilege with
.Nm zfs Cm allow ,
can access all groups' usage.
.It Sy projectused Ns @ Ns Em project
The amount of space consumed by the specified project in this dataset. Project
is identified via the project identifier (ID) that is object-based numeral
attribute. An object can inherit the project ID from its parent object (if the
parent has the flag of inherit project ID that can be set and changed via
.Nm chattr Fl /+P
or
.Nm zfs project Fl s )
when being created. The privileged user can set and change object's project
ID via
.Nm chattr Fl p
or
.Nm zfs project Fl s
anytime. Space is charged to the project of each file, as displayed by
.Nm lsattr Fl p
or
.Nm zfs project .
See the
.Sy userused Ns @ Ns Em user
property for more information.
.Pp
The root user, or a user who has been granted the
.Sy projectused
privilege with
.Nm zfs allow ,
can access all projects' usage.
.It Sy projectobjused Ns @ Ns Em project
The
.Sy projectobjused
is similar to
.Sy projectused
but instead it counts the number of objects consumed by project. When the
property
.Sy xattr=on
is set on a fileset, ZFS will create additional objects per-file to store
extended attributes. These additional objects are reflected in the
.Sy projectobjused
value and are counted against the project's
.Sy projectobjquota .
When a filesystem is configured to use
.Sy xattr=sa
no additional internal objects are required. See the
.Sy userobjused Ns @ Ns Em user
property for more information.
.Pp
The root user, or a user who has been granted the
.Sy projectobjused
privilege with
.Nm zfs allow ,
can access all projects' objects usage.
.It Sy volblocksize
For volumes, specifies the block size of the volume.
The
.Sy blocksize
cannot be changed once the volume has been written, so it should be set at
volume creation time.
The default
.Sy blocksize
for volumes is 8 Kbytes.
Any power of 2 from 512 bytes to 128 Kbytes is valid.
.Pp
This property can also be referred to by its shortened column name,
.Sy volblock .
.It Sy written
The amount of space
.Sy referenced
by this dataset, that was written since the previous snapshot
.Pq i.e. that is not referenced by the previous snapshot .
.It Sy written Ns @ Ns Em snapshot
The amount of
.Sy referenced
space written to this dataset since the specified snapshot.
This is the space that is referenced by this dataset but was not referenced by
the specified snapshot.
.Pp
The
.Em snapshot
may be specified as a short snapshot name
.Po just the part after the
.Sy @
.Pc ,
in which case it will be interpreted as a snapshot in the same filesystem as
this dataset.
The
.Em snapshot
may be a full snapshot name
.Po Em filesystem Ns @ Ns Em snapshot Pc ,
which for clones may be a snapshot in the origin's filesystem
.Pq or the origin of the origin's filesystem, etc.
.El
.Pp
The following native properties can be used to change the behavior of a ZFS
dataset.
.Bl -tag -width ""
.It Xo
.Sy aclinherit Ns = Ns Sy discard Ns | Ns Sy noallow Ns | Ns
.Sy restricted Ns | Ns Sy passthrough Ns | Ns Sy passthrough-x
.Xc
Controls how ACEs are inherited when files and directories are created.
.Bl -tag -width "passthrough-x"
.It Sy discard
does not inherit any ACEs.
.It Sy noallow
only inherits inheritable ACEs that specify
.Qq deny
permissions.
.It Sy restricted
default, removes the
.Sy write_acl
and
.Sy write_owner
permissions when the ACE is inherited.
.It Sy passthrough
inherits all inheritable ACEs without any modifications.
.It Sy passthrough-x
same meaning as
.Sy passthrough ,
except that the
.Sy owner@ ,
.Sy group@ ,
and
.Sy everyone@
ACEs inherit the execute permission only if the file creation mode also requests
the execute bit.
.El
.Pp
When the property value is set to
.Sy passthrough ,
files are created with a mode determined by the inheritable ACEs.
If no inheritable ACEs exist that affect the mode, then the mode is set in
accordance to the requested mode from the application.
.Pp
The
.Sy aclinherit
property does not apply to POSIX ACLs.
.It Xo
.Sy aclmode Ns = Ns Sy discard Ns | Ns Sy groupmask Ns | Ns
.Sy passthrough Ns | Ns Sy restricted Ns
.Xc
Controls how an ACL is modified during chmod(2) and how inherited ACEs
are modified by the file creation mode.
.Bl -tag -width "passthrough"
.It Sy discard
default, deletes all
.Sy ACEs
except for those representing
the mode of the file or directory requested by
.Xr chmod 2 .
.It Sy groupmask
reduces permissions granted in all
.Sy ALLOW
entries found in the
.Sy ACL
such that they are no greater than the group permissions specified by
.Xr chmod 2 .
.It Sy passthrough
indicates that no changes are made to the
.Tn ACL
other than creating or updating the necessary
.Tn ACL
entries to represent the new mode of the file or directory.
.It Sy restricted
will cause the
.Xr chmod 2
operation to return an error when used on any file or directory which has
a non-trivial
.Tn ACL
whose entries can not be represented by a mode.
.Xr chmod 2
is required to change the set user ID, set group ID, or sticky bits on a file
or directory, as they do not have equivalent
.Tn ACL
entries.
In order to use
.Xr chmod 2
on a file or directory with a non-trivial
.Tn ACL
when
.Sy aclmode
is set to
.Sy restricted ,
you must first remove all
.Tn ACL
entries which do not represent the current mode.
.El
.It Sy acltype Ns = Ns Sy off Ns | Ns Sy nfsv4 Ns | Ns Sy posix
Controls whether ACLs are enabled and if so what type of ACL to use.
When this property is set to a type of ACL not supported by the current
platform, the behavior is the same as if it were set to
.Sy off .
.Bl -tag -width "posixacl"
.It Sy off
default on Linux, when a file system has the
.Sy acltype
property set to off then ACLs are disabled.
.It Sy noacl
an alias for
.Sy off
.It Sy nfsv4
default on FreeBSD, indicates that NFSv4-style ZFS ACLs should be used.
These ACLs can be managed with the
.Xr getfacl 1
and
.Xr setfacl 1
commands on FreeBSD. The
.Sy nfsv4
ZFS ACL type is not yet supported on Linux.
.It Sy posix
indicates POSIX ACLs should be used. POSIX ACLs are specific to Linux and are
not functional on other platforms. POSIX ACLs are stored as an extended
attribute and therefore will not overwrite any existing NFSv4 ACLs which
may be set.
.It Sy posixacl
an alias for
.Sy posix
.El
.Pp
To obtain the best performance when setting
.Sy posix
users are strongly encouraged to set the
.Sy xattr=sa
property. This will result in the POSIX ACL being stored more efficiently on
disk. But as a consequence, all new extended attributes will only be
accessible from OpenZFS implementations which support the
.Sy xattr=sa
property. See the
.Sy xattr
property for more details.
.It Sy atime Ns = Ns Sy on Ns | Ns Sy off
Controls whether the access time for files is updated when they are read.
Turning this property off avoids producing write traffic when reading files and
can result in significant performance gains, though it might confuse mailers
and other similar utilities. The values
.Sy on
and
.Sy off
are equivalent to the
.Sy atime
and
.Sy noatime
mount options. The default value is
.Sy on .
See also
.Sy relatime
below.
.It Sy canmount Ns = Ns Sy on Ns | Ns Sy off Ns | Ns Sy noauto
If this property is set to
.Sy off ,
the file system cannot be mounted, and is ignored by
.Nm zfs Cm mount Fl a .
Setting this property to
.Sy off
is similar to setting the
.Sy mountpoint
property to
.Sy none ,
except that the dataset still has a normal
.Sy mountpoint
property, which can be inherited.
Setting this property to
.Sy off
allows datasets to be used solely as a mechanism to inherit properties.
One example of setting
.Sy canmount Ns = Ns Sy off
is to have two datasets with the same
.Sy mountpoint ,
so that the children of both datasets appear in the same directory, but might
have different inherited characteristics.
.Pp
When set to
.Sy noauto ,
a dataset can only be mounted and unmounted explicitly.
The dataset is not mounted automatically when the dataset is created or
imported, nor is it mounted by the
.Nm zfs Cm mount Fl a
command or unmounted by the
.Nm zfs Cm unmount Fl a
command.
.Pp
This property is not inherited.
.It Xo
.Sy checksum Ns = Ns Sy on Ns | Ns Sy off Ns | Ns Sy fletcher2 Ns | Ns
.Sy fletcher4 Ns | Ns Sy sha256 Ns | Ns Sy noparity Ns | Ns
.Sy sha512 Ns | Ns Sy skein Ns | Ns Sy edonr
.Xc
Controls the checksum used to verify data integrity.
The default value is
.Sy on ,
which automatically selects an appropriate algorithm
.Po currently,
.Sy fletcher4 ,
but this may change in future releases
.Pc .
The value
.Sy off
disables integrity checking on user data.
The value
.Sy noparity
not only disables integrity but also disables maintaining parity for user data.
This setting is used internally by a dump device residing on a RAID-Z pool and
should not be used by any other dataset.
Disabling checksums is
.Sy NOT
a recommended practice.
.Pp
The
.Sy sha512 ,
.Sy skein ,
and
.Sy edonr
checksum algorithms require enabling the appropriate features on the pool.
FreeBSD does not support the
.Sy edonr
algorithm.
.Pp
Please see
.Xr zpool-features 5
for more information on these algorithms.
.Pp
Changing this property affects only newly-written data.
.It Xo
.Sy compression Ns = Ns Sy on Ns | Ns Sy off Ns | Ns Sy gzip Ns | Ns
.Sy gzip- Ns Em N Ns | Ns Sy lz4 Ns | Ns Sy lzjb Ns | Ns Sy zle Ns | Ns Sy zstd Ns | Ns
.Sy zstd- Ns Em N Ns | Ns Sy zstd-fast Ns | Ns Sy zstd-fast- Ns Em N
.Xc
Controls the compression algorithm used for this dataset.
.Pp
Setting compression to
.Sy on
indicates that the current default compression algorithm should be used.
The default balances compression and decompression speed, with compression ratio
and is expected to work well on a wide variety of workloads.
Unlike all other settings for this property,
.Sy on
does not select a fixed compression type.
As new compression algorithms are added to ZFS and enabled on a pool, the
default compression algorithm may change.
The current default compression algorithm is either
.Sy lzjb
or, if the
.Sy lz4_compress
feature is enabled,
.Sy lz4 .
.Pp
The
.Sy lz4
compression algorithm is a high-performance replacement for the
.Sy lzjb
algorithm.
It features significantly faster compression and decompression, as well as a
moderately higher compression ratio than
.Sy lzjb ,
but can only be used on pools with the
.Sy lz4_compress
feature set to
.Sy enabled .
See
.Xr zpool-features 5
for details on ZFS feature flags and the
.Sy lz4_compress
feature.
.Pp
The
.Sy lzjb
compression algorithm is optimized for performance while providing decent data
compression.
.Pp
The
.Sy gzip
compression algorithm uses the same compression as the
.Xr gzip 1
command.
You can specify the
.Sy gzip
level by using the value
.Sy gzip- Ns Em N ,
where
.Em N
is an integer from 1
.Pq fastest
to 9
.Pq best compression ratio .
Currently,
.Sy gzip
is equivalent to
.Sy gzip-6
.Po which is also the default for
.Xr gzip 1
.Pc .
.Pp
The
.Sy zstd
compression algorithm provides both high compression ratios and good
performance. You can specify the
.Sy zstd
level by using the value
.Sy zstd- Ns Em N ,
where
.Em N
is an integer from 1
.Pq fastest
to 19
.Pq best compression ratio .
.Sy zstd
is equivalent to
.Sy zstd-3 .
.Pp
Faster speeds at the cost of the compression ratio can be requested by
setting a negative
.Sy zstd
level. This is done using
.Sy zstd-fast- Ns Em N ,
where
.Em N
is an integer in [1-9,10,20,30,...,100,500,1000] which maps to a negative
.Sy zstd
level. The lower the level the faster the compression - 1000 provides
the fastest compression and lowest compression ratio.
.Sy zstd-fast
is equivalent to
.Sy zstd-fast-1 .
.Pp
The
.Sy zle
compression algorithm compresses runs of zeros.
.Pp
This property can also be referred to by its shortened column name
.Sy compress .
Changing this property affects only newly-written data.
.Pp
When any setting except
.Sy off
is selected, compression will explicitly check for blocks consisting of only
zeroes (the NUL byte). When a zero-filled block is detected, it is stored as
a hole and not compressed using the indicated compression algorithm.
.Pp
Any block being compressed must be no larger than 7/8 of its original size
after compression, otherwise the compression will not be considered worthwhile
and the block saved uncompressed. Note that when the logical block is less than
8 times the disk sector size this effectively reduces the necessary compression
ratio; for example 8k blocks on disks with 4k disk sectors must compress to 1/2
or less of their original size.
.It Xo
.Sy context Ns = Ns Sy none Ns | Ns
.Em SELinux_User:SElinux_Role:Selinux_Type:Sensitivity_Level
.Xc
This flag sets the SELinux context for all files in the file system under
a mount point for that file system. See
.Xr selinux 8
for more information.
.It Xo
.Sy fscontext Ns = Ns Sy none Ns | Ns
.Em SELinux_User:SElinux_Role:Selinux_Type:Sensitivity_Level
.Xc
This flag sets the SELinux context for the file system file system being
mounted. See
.Xr selinux 8
for more information.
.It Xo
.Sy defcontext Ns = Ns Sy none Ns | Ns
.Em SELinux_User:SElinux_Role:Selinux_Type:Sensitivity_Level
.Xc
This flag sets the SELinux default context for unlabeled files. See
.Xr selinux 8
for more information.
.It Xo
.Sy rootcontext Ns = Ns Sy none Ns | Ns
.Em SELinux_User:SElinux_Role:Selinux_Type:Sensitivity_Level
.Xc
This flag sets the SELinux context for the root inode of the file system. See
.Xr selinux 8
for more information.
.It Sy copies Ns = Ns Sy 1 Ns | Ns Sy 2 Ns | Ns Sy 3
Controls the number of copies of data stored for this dataset.
These copies are in addition to any redundancy provided by the pool, for
example, mirroring or RAID-Z.
The copies are stored on different disks, if possible.
The space used by multiple copies is charged to the associated file and dataset,
changing the
.Sy used
property and counting against quotas and reservations.
.Pp
Changing this property only affects newly-written data.
Therefore, set this property at file system creation time by using the
.Fl o Sy copies Ns = Ns Ar N
option.
.Pp
Remember that ZFS will not import a pool with a missing top-level vdev. Do
.Sy NOT
create, for example a two-disk striped pool and set
.Sy copies=2
on some datasets thinking you have setup redundancy for them. When a disk
fails you will not be able to import the pool and will have lost all of your
data.
.Pp
Encrypted datasets may not have
.Sy copies Ns = Ns Em 3
since the implementation stores some encryption metadata where the third copy
would normally be.
.It Sy devices Ns = Ns Sy on Ns | Ns Sy off
Controls whether device nodes can be opened on this file system.
The default value is
.Sy on .
The values
.Sy on
and
.Sy off
are equivalent to the
.Sy dev
and
.Sy nodev
mount options.
.It Xo
.Sy dedup Ns = Ns Sy off Ns | Ns Sy on Ns | Ns Sy verify Ns | Ns
.Sy sha256[,verify] Ns | Ns Sy sha512[,verify] Ns | Ns Sy skein[,verify] Ns | Ns
.Sy edonr,verify
.Xc
Configures deduplication for a dataset. The default value is
.Sy off .
The default deduplication checksum is
.Sy sha256
(this may change in the future). When
.Sy dedup
is enabled, the checksum defined here overrides the
.Sy checksum
property. Setting the value to
.Sy verify
has the same effect as the setting
.Sy sha256,verify.
.Pp
If set to
.Sy verify ,
ZFS will do a byte-to-byte comparison in case of two blocks having the same
signature to make sure the block contents are identical. Specifying
.Sy verify
is mandatory for the
.Sy edonr
algorithm.
.Pp
Unless necessary, deduplication should NOT be enabled on a system. See the
.Em Deduplication
section of
.Xr zfsconcepts 8 .
.It Xo
.Sy dnodesize Ns = Ns Sy legacy Ns | Ns Sy auto Ns | Ns Sy 1k Ns | Ns
.Sy 2k Ns | Ns Sy 4k Ns | Ns Sy 8k Ns | Ns Sy 16k
.Xc
Specifies a compatibility mode or literal value for the size of dnodes in the
file system. The default value is
.Sy legacy .
Setting this property to a value other than
.Sy legacy
requires the large_dnode pool feature to be enabled.
.Pp
Consider setting
.Sy dnodesize
to
.Sy auto
if the dataset uses the
.Sy xattr=sa
property setting and the workload makes heavy use of extended attributes. This
may be applicable to SELinux-enabled systems, Lustre servers, and Samba
servers, for example. Literal values are supported for cases where the optimal
size is known in advance and for performance testing.
.Pp
Leave
.Sy dnodesize
set to
.Sy legacy
if you need to receive a send stream of this dataset on a pool that doesn't
enable the large_dnode feature, or if you need to import this pool on a system
that doesn't support the large_dnode feature.
.Pp
This property can also be referred to by its shortened column name,
.Sy dnsize .
.It Xo
.Sy encryption Ns = Ns Sy off Ns | Ns Sy on Ns | Ns Sy aes-128-ccm Ns | Ns
.Sy aes-192-ccm Ns | Ns Sy aes-256-ccm Ns | Ns Sy aes-128-gcm Ns | Ns
.Sy aes-192-gcm Ns | Ns Sy aes-256-gcm
.Xc
Controls the encryption cipher suite (block cipher, key length, and mode) used
for this dataset. Requires the
.Sy encryption
feature to be enabled on the pool.
Requires a
.Sy keyformat
to be set at dataset creation time.
.Pp
Selecting
.Sy encryption Ns = Ns Sy on
when creating a dataset indicates that the default encryption suite will be
selected, which is currently
.Sy aes-256-gcm .
In order to provide consistent data protection, encryption must be specified at
dataset creation time and it cannot be changed afterwards.
.Pp
For more details and caveats about encryption see the
.Em Encryption
section of
.Xr zfs-load-key 8 .
.It Sy keyformat Ns = Ns Sy raw Ns | Ns Sy hex Ns | Ns Sy passphrase
Controls what format the user's encryption key will be provided as. This
property is only set when the dataset is encrypted.
.Pp
Raw keys and hex keys must be 32 bytes long (regardless of the chosen
encryption suite) and must be randomly generated. A raw key can be generated
with the following command:
.Bd -literal
# dd if=/dev/urandom of=/path/to/output/key bs=32 count=1
.Ed
.Pp
Passphrases must be between 8 and 512 bytes long and will be processed through
PBKDF2 before being used (see the
.Sy pbkdf2iters
property). Even though the
encryption suite cannot be changed after dataset creation, the keyformat can be
with
.Nm zfs Cm change-key .
.It Xo
.Sy keylocation Ns = Ns Sy prompt Ns | Ns Sy file:// Ns Em </absolute/file/path>
.Xc
Controls where the user's encryption key will be loaded from by default for
commands such as
.Nm zfs Cm load-key
and
.Nm zfs Cm mount Cm -l .
This property is only set for encrypted datasets which are encryption roots. If
unspecified, the default is
.Sy prompt.
.Pp
Even though the encryption suite cannot be changed after dataset creation, the
keylocation can be with either
.Nm zfs Cm set
or
.Nm zfs Cm change-key .
If
.Sy prompt
is selected ZFS will ask for the key at the command prompt when it is required
to access the encrypted data (see
.Nm zfs Cm load-key
for details). This setting will also allow the key to be passed in via STDIN,
but users should be careful not to place keys which should be kept secret on
the command line. If a file URI is selected, the key will be loaded from the
specified absolute file path.
.It Sy pbkdf2iters Ns = Ns Ar iterations
Controls the number of PBKDF2 iterations that a
.Sy passphrase
encryption key should be run through when processing it into an encryption key.
This property is only defined when encryption is enabled and a keyformat of
.Sy passphrase
is selected. The goal of PBKDF2 is to significantly increase the
computational difficulty needed to brute force a user's passphrase. This is
accomplished by forcing the attacker to run each passphrase through a
computationally expensive hashing function many times before they arrive at the
resulting key. A user who actually knows the passphrase will only have to pay
this cost once. As CPUs become better at processing, this number should be
raised to ensure that a brute force attack is still not possible. The current
default is
.Sy 350000
and the minimum is
.Sy 100000 .
This property may be changed with
.Nm zfs Cm change-key .
.It Sy exec Ns = Ns Sy on Ns | Ns Sy off
Controls whether processes can be executed from within this file system.
The default value is
.Sy on .
The values
.Sy on
and
.Sy off
are equivalent to the
.Sy exec
and
.Sy noexec
mount options.
.It Sy filesystem_limit Ns = Ns Em count Ns | Ns Sy none
Limits the number of filesystems and volumes that can exist under this point in
the dataset tree.
The limit is not enforced if the user is allowed to change the limit.
Setting a
.Sy filesystem_limit
to
.Sy on
a descendent of a filesystem that already has a
.Sy filesystem_limit
does not override the ancestor's
.Sy filesystem_limit ,
but rather imposes an additional limit.
This feature must be enabled to be used
.Po see
.Xr zpool-features 5
.Pc .
.It Sy special_small_blocks Ns = Ns Em size
This value represents the threshold block size for including small file
blocks into the special allocation class. Blocks smaller than or equal to this
value will be assigned to the special allocation class while greater blocks
will be assigned to the regular class. Valid values are zero or a power of two
from 512B up to 1M. The default size is 0 which means no small file blocks
will be allocated in the special class.
.Pp
Before setting this property, a special class vdev must be added to the
pool. See
.Xr zpool 8
for more details on the special allocation class.
.It Sy mountpoint Ns = Ns Pa path Ns | Ns Sy none Ns | Ns Sy legacy
Controls the mount point used for this file system.
See the
.Em Mount Points
section of
.Xr zfsconcepts 8
for more information on how this property is used.
.Pp
When the
.Sy mountpoint
property is changed for a file system, the file system and any children that
inherit the mount point are unmounted.
If the new value is
.Sy legacy ,
then they remain unmounted.
Otherwise, they are automatically remounted in the new location if the property
was previously
.Sy legacy
or
.Sy none ,
or if they were mounted before the property was changed.
In addition, any shared file systems are unshared and shared in the new
location.
.It Sy nbmand Ns = Ns Sy on Ns | Ns Sy off
Controls whether the file system should be mounted with
.Sy nbmand
.Pq Non Blocking mandatory locks .
This is used for SMB clients.
Changes to this property only take effect when the file system is umounted and
remounted.
See
.Xr mount 8
for more information on
.Sy nbmand
mounts. This property is not used on Linux.
.It Sy overlay Ns = Ns Sy on Ns | Ns Sy off
Allow mounting on a busy directory or a directory which already contains
files or directories.
This is the default mount behavior for Linux and FreeBSD file systems.
On these platforms the property is
.Sy on
by default.
Set to
.Sy off
to disable overlay mounts for consistency with OpenZFS on other platforms.
.It Sy primarycache Ns = Ns Sy all Ns | Ns Sy none Ns | Ns Sy metadata
Controls what is cached in the primary cache
.Pq ARC .
If this property is set to
.Sy all ,
then both user data and metadata is cached.
If this property is set to
.Sy none ,
then neither user data nor metadata is cached.
If this property is set to
.Sy metadata ,
then only metadata is cached.
The default value is
.Sy all .
.It Sy quota Ns = Ns Em size Ns | Ns Sy none
Limits the amount of space a dataset and its descendents can consume.
This property enforces a hard limit on the amount of space used.
This includes all space consumed by descendents, including file systems and
snapshots.
Setting a quota on a descendent of a dataset that already has a quota does not
override the ancestor's quota, but rather imposes an additional limit.
.Pp
Quotas cannot be set on volumes, as the
.Sy volsize
property acts as an implicit quota.
.It Sy snapshot_limit Ns = Ns Em count Ns | Ns Sy none
Limits the number of snapshots that can be created on a dataset and its
descendents.
Setting a
.Sy snapshot_limit
on a descendent of a dataset that already has a
.Sy snapshot_limit
does not override the ancestor's
.Sy snapshot_limit ,
but rather imposes an additional limit.
The limit is not enforced if the user is allowed to change the limit.
For example, this means that recursive snapshots taken from the global zone are
counted against each delegated dataset within a zone.
This feature must be enabled to be used
.Po see
.Xr zpool-features 5
.Pc .
.It Sy userquota@ Ns Em user Ns = Ns Em size Ns | Ns Sy none
Limits the amount of space consumed by the specified user.
User space consumption is identified by the
.Sy userspace@ Ns Em user
property.
.Pp
Enforcement of user quotas may be delayed by several seconds.
This delay means that a user might exceed their quota before the system notices
that they are over quota and begins to refuse additional writes with the
.Er EDQUOT
error message.
See the
.Nm zfs Cm userspace
subcommand for more information.
.Pp
Unprivileged users can only access their own groups' space usage.
The root user, or a user who has been granted the
.Sy userquota
privilege with
.Nm zfs Cm allow ,
can get and set everyone's quota.
.Pp
This property is not available on volumes, on file systems before version 4, or
on pools before version 15.
The
.Sy userquota@ Ns Em ...
properties are not displayed by
.Nm zfs Cm get Sy all .
The user's name must be appended after the
.Sy @
symbol, using one of the following forms:
.Bl -bullet
.It
.Em POSIX name
.Po for example,
.Sy joe
.Pc
.It
.Em POSIX numeric ID
.Po for example,
.Sy 789
.Pc
.It
.Em SID name
.Po for example,
.Sy joe.smith@mydomain
.Pc
.It
.Em SID numeric ID
.Po for example,
.Sy S-1-123-456-789
.Pc
.El
.Pp
Files created on Linux always have POSIX owners.
.It Sy userobjquota@ Ns Em user Ns = Ns Em size Ns | Ns Sy none
The
.Sy userobjquota
is similar to
.Sy userquota
but it limits the number of objects a user can create. Please refer to
.Sy userobjused
for more information about how objects are counted.
.It Sy groupquota@ Ns Em group Ns = Ns Em size Ns | Ns Sy none
Limits the amount of space consumed by the specified group.
Group space consumption is identified by the
.Sy groupused@ Ns Em group
property.
.Pp
Unprivileged users can access only their own groups' space usage.
The root user, or a user who has been granted the
.Sy groupquota
privilege with
.Nm zfs Cm allow ,
can get and set all groups' quotas.
.It Sy groupobjquota@ Ns Em group Ns = Ns Em size Ns | Ns Sy none
The
.Sy groupobjquota
is similar to
.Sy groupquota
but it limits number of objects a group can consume. Please refer to
.Sy userobjused
for more information about how objects are counted.
.It Sy projectquota@ Ns Em project Ns = Ns Em size Ns | Ns Sy none
Limits the amount of space consumed by the specified project. Project
space consumption is identified by the
.Sy projectused@ Ns Em project
property. Please refer to
.Sy projectused
for more information about how project is identified and set/changed.
.Pp
The root user, or a user who has been granted the
.Sy projectquota
privilege with
.Nm zfs allow ,
can access all projects' quota.
.It Sy projectobjquota@ Ns Em project Ns = Ns Em size Ns | Ns Sy none
The
.Sy projectobjquota
is similar to
.Sy projectquota
but it limits number of objects a project can consume. Please refer to
.Sy userobjused
for more information about how objects are counted.
.It Sy readonly Ns = Ns Sy on Ns | Ns Sy off
Controls whether this dataset can be modified.
The default value is
.Sy off .
The values
.Sy on
and
.Sy off
are equivalent to the
.Sy ro
and
.Sy rw
mount options.
.Pp
This property can also be referred to by its shortened column name,
.Sy rdonly .
.It Sy recordsize Ns = Ns Em size
Specifies a suggested block size for files in the file system.
This property is designed solely for use with database workloads that access
files in fixed-size records.
ZFS automatically tunes block sizes according to internal algorithms optimized
for typical access patterns.
.Pp
For databases that create very large files but access them in small random
chunks, these algorithms may be suboptimal.
Specifying a
.Sy recordsize
greater than or equal to the record size of the database can result in
significant performance gains.
Use of this property for general purpose file systems is strongly discouraged,
and may adversely affect performance.
.Pp
The size specified must be a power of two greater than or equal to 512 and less
than or equal to 128 Kbytes.
If the
.Sy large_blocks
feature is enabled on the pool, the size may be up to 1 Mbyte.
See
.Xr zpool-features 5
for details on ZFS feature flags.
.Pp
Changing the file system's
.Sy recordsize
affects only files created afterward; existing files are unaffected.
.Pp
This property can also be referred to by its shortened column name,
.Sy recsize .
.It Sy redundant_metadata Ns = Ns Sy all Ns | Ns Sy most
Controls what types of metadata are stored redundantly.
ZFS stores an extra copy of metadata, so that if a single block is corrupted,
the amount of user data lost is limited.
This extra copy is in addition to any redundancy provided at the pool level
.Pq e.g. by mirroring or RAID-Z ,
and is in addition to an extra copy specified by the
.Sy copies
property
.Pq up to a total of 3 copies .
For example if the pool is mirrored,
.Sy copies Ns = Ns 2 ,
and
.Sy redundant_metadata Ns = Ns Sy most ,
then ZFS stores 6 copies of most metadata, and 4 copies of data and some
metadata.
.Pp
When set to
.Sy all ,
ZFS stores an extra copy of all metadata.
If a single on-disk block is corrupt, at worst a single block of user data
.Po which is
.Sy recordsize
bytes long
.Pc
can be lost.
.Pp
When set to
.Sy most ,
ZFS stores an extra copy of most types of metadata.
This can improve performance of random writes, because less metadata must be
written.
In practice, at worst about 100 blocks
.Po of
.Sy recordsize
bytes each
.Pc
of user data can be lost if a single on-disk block is corrupt.
The exact behavior of which metadata blocks are stored redundantly may change in
future releases.
.Pp
The default value is
.Sy all .
.It Sy refquota Ns = Ns Em size Ns | Ns Sy none
Limits the amount of space a dataset can consume.
This property enforces a hard limit on the amount of space used.
This hard limit does not include space used by descendents, including file
systems and snapshots.
.It Sy refreservation Ns = Ns Em size Ns | Ns Sy none Ns | Ns Sy auto
The minimum amount of space guaranteed to a dataset, not including its
descendents.
When the amount of space used is below this value, the dataset is treated as if
it were taking up the amount of space specified by
.Sy refreservation .
The
.Sy refreservation
reservation is accounted for in the parent datasets' space used, and counts
against the parent datasets' quotas and reservations.
.Pp
If
.Sy refreservation
is set, a snapshot is only allowed if there is enough free pool space outside of
this reservation to accommodate the current number of
.Qq referenced
bytes in the dataset.
.Pp
If
.Sy refreservation
is set to
.Sy auto ,
a volume is thick provisioned
.Po or
.Qq not sparse
.Pc .
.Sy refreservation Ns = Ns Sy auto
is only supported on volumes.
See
.Sy volsize
in the
.Sx Native Properties
section for more information about sparse volumes.
.Pp
This property can also be referred to by its shortened column name,
.Sy refreserv .
.It Sy relatime Ns = Ns Sy on Ns | Ns Sy off
Controls the manner in which the access time is updated when
.Sy atime=on
is set. Turning this property on causes the access time to be updated relative
to the modify or change time. Access time is only updated if the previous
access time was earlier than the current modify or change time or if the
existing access time hasn't been updated within the past 24 hours. The default
value is
.Sy off .
The values
.Sy on
and
.Sy off
are equivalent to the
.Sy relatime
and
.Sy norelatime
mount options.
.It Sy reservation Ns = Ns Em size Ns | Ns Sy none
The minimum amount of space guaranteed to a dataset and its descendants.
When the amount of space used is below this value, the dataset is treated as if
it were taking up the amount of space specified by its reservation.
Reservations are accounted for in the parent datasets' space used, and count
against the parent datasets' quotas and reservations.
.Pp
This property can also be referred to by its shortened column name,
.Sy reserv .
.It Sy secondarycache Ns = Ns Sy all Ns | Ns Sy none Ns | Ns Sy metadata
Controls what is cached in the secondary cache
.Pq L2ARC .
If this property is set to
.Sy all ,
then both user data and metadata is cached.
If this property is set to
.Sy none ,
then neither user data nor metadata is cached.
If this property is set to
.Sy metadata ,
then only metadata is cached.
The default value is
.Sy all .
.It Sy setuid Ns = Ns Sy on Ns | Ns Sy off
Controls whether the setuid bit is respected for the file system.
The default value is
.Sy on .
The values
.Sy on
and
.Sy off
are equivalent to the
.Sy suid
and
.Sy nosuid
mount options.
.It Sy sharesmb Ns = Ns Sy on Ns | Ns Sy off Ns | Ns Em opts
Controls whether the file system is shared by using
.Sy Samba USERSHARES
and what options are to be used. Otherwise, the file system is automatically
shared and unshared with the
.Nm zfs Cm share
and
.Nm zfs Cm unshare
commands. If the property is set to on, the
.Xr net 8
command is invoked to create a
.Sy USERSHARE .
.Pp
Because SMB shares requires a resource name, a unique resource name is
constructed from the dataset name. The constructed name is a copy of the
dataset name except that the characters in the dataset name, which would be
invalid in the resource name, are replaced with underscore (_) characters.
Linux does not currently support additional options which might be available
on Solaris.
.Pp
If the
.Sy sharesmb
property is set to
.Sy off ,
the file systems are unshared.
.Pp
The share is created with the ACL (Access Control List) "Everyone:F" ("F"
stands for "full permissions", ie. read and write permissions) and no guest
access (which means Samba must be able to authenticate a real user, system
passwd/shadow, LDAP or smbpasswd based) by default. This means that any
additional access control (disallow specific user specific access etc) must
be done on the underlying file system.
.It Sy sharenfs Ns = Ns Sy on Ns | Ns Sy off Ns | Ns Em opts
Controls whether the file system is shared via NFS, and what options are to be
used.
A file system with a
.Sy sharenfs
property of
.Sy off
is managed with the
.Xr exportfs 8
command and entries in the
.Em /etc/exports
file.
Otherwise, the file system is automatically shared and unshared with the
.Nm zfs Cm share
and
.Nm zfs Cm unshare
commands.
If the property is set to
.Sy on ,
the dataset is shared using the default options:
.Pp
.Em sec=sys,rw,crossmnt,no_subtree_check
.Pp
See
.Xr exports 5
for the meaning of the default options. Otherwise, the
.Xr exportfs 8
command is invoked with options equivalent to the contents of this property.
.Pp
When the
.Sy sharenfs
property is changed for a dataset, the dataset and any children inheriting the
property are re-shared with the new options, only if the property was previously
.Sy off ,
or if they were shared before the property was changed.
If the new property is
.Sy off ,
the file systems are unshared.
.It Sy logbias Ns = Ns Sy latency Ns | Ns Sy throughput
Provide a hint to ZFS about handling of synchronous requests in this dataset.
If
.Sy logbias
is set to
.Sy latency
.Pq the default ,
ZFS will use pool log devices
.Pq if configured
to handle the requests at low latency.
If
.Sy logbias
is set to
.Sy throughput ,
ZFS will not use configured pool log devices.
ZFS will instead optimize synchronous operations for global pool throughput and
efficient use of resources.
.It Sy snapdev Ns = Ns Sy hidden Ns | Ns Sy visible
Controls whether the volume snapshot devices under
.Em /dev/zvol/<pool>
are hidden or visible. The default value is
.Sy hidden .
.It Sy snapdir Ns = Ns Sy hidden Ns | Ns Sy visible
Controls whether the
.Pa .zfs
directory is hidden or visible in the root of the file system as discussed in
the
.Em Snapshots
section of
.Xr zfsconcepts 8 .
The default value is
.Sy hidden .
.It Sy sync Ns = Ns Sy standard Ns | Ns Sy always Ns | Ns Sy disabled
Controls the behavior of synchronous requests
.Pq e.g. fsync, O_DSYNC .
.Sy standard
is the
.Tn POSIX
specified behavior of ensuring all synchronous requests are written to stable
storage and all devices are flushed to ensure data is not cached by device
controllers
.Pq this is the default .
.Sy always
causes every file system transaction to be written and flushed before its
system call returns.
This has a large performance penalty.
.Sy disabled
disables synchronous requests.
File system transactions are only committed to stable storage periodically.
This option will give the highest performance.
However, it is very dangerous as ZFS would be ignoring the synchronous
transaction demands of applications such as databases or NFS.
Administrators should only use this option when the risks are understood.
.It Sy version Ns = Ns Em N Ns | Ns Sy current
The on-disk version of this file system, which is independent of the pool
version.
This property can only be set to later supported versions.
See the
.Nm zfs Cm upgrade
command.
.It Sy volsize Ns = Ns Em size
For volumes, specifies the logical size of the volume.
By default, creating a volume establishes a reservation of equal size.
For storage pools with a version number of 9 or higher, a
.Sy refreservation
is set instead.
Any changes to
.Sy volsize
are reflected in an equivalent change to the reservation
.Po or
.Sy refreservation
.Pc .
The
.Sy volsize
can only be set to a multiple of
.Sy volblocksize ,
and cannot be zero.
.Pp
The reservation is kept equal to the volume's logical size to prevent unexpected
behavior for consumers.
Without the reservation, the volume could run out of space, resulting in
undefined behavior or data corruption, depending on how the volume is used.
These effects can also occur when the volume size is changed while it is in use
.Pq particularly when shrinking the size .
Extreme care should be used when adjusting the volume size.
.Pp
Though not recommended, a
.Qq sparse volume
.Po also known as
.Qq thin provisioned
.Pc
can be created by specifying the
.Fl s
option to the
.Nm zfs Cm create Fl V
command, or by changing the value of the
.Sy refreservation
property
.Po or
.Sy reservation
property on pool version 8 or earlier
.Pc
after the volume has been created.
A
.Qq sparse volume
is a volume where the value of
.Sy refreservation
is less than the size of the volume plus the space required to store its
metadata.
Consequently, writes to a sparse volume can fail with
.Er ENOSPC
when the pool is low on space.
For a sparse volume, changes to
.Sy volsize
are not reflected in the
.Sy refreservation.
A volume that is not sparse is said to be
.Qq thick provisioned .
A sparse volume can become thick provisioned by setting
.Sy refreservation
to
.Sy auto .
.It Sy volmode Ns = Ns Cm default | full | geom | dev | none
This property specifies how volumes should be exposed to the OS.
Setting it to
.Sy full
exposes volumes as fully fledged block devices, providing maximal
functionality. The value
.Sy geom
is just an alias for
.Sy full
and is kept for compatibility.
Setting it to
.Sy dev
hides its partitions.
Volumes with property set to
.Sy none
are not exposed outside ZFS, but can be snapshotted, cloned, replicated, etc,
that can be suitable for backup purposes.
Value
.Sy default
means that volumes exposition is controlled by system-wide tunable
.Va zvol_volmode ,
where
.Sy full ,
.Sy dev
and
.Sy none
are encoded as 1, 2 and 3 respectively.
The default value is
.Sy full .
.It Sy vscan Ns = Ns Sy on Ns | Ns Sy off
Controls whether regular files should be scanned for viruses when a file is
opened and closed.
In addition to enabling this property, the virus scan service must also be
enabled for virus scanning to occur.
The default value is
.Sy off .
This property is not used on Linux.
.It Sy xattr Ns = Ns Sy on Ns | Ns Sy off Ns | Ns Sy sa
Controls whether extended attributes are enabled for this file system. Two
styles of extended attributes are supported either directory based or system
attribute based.
.Pp
The default value of
.Sy on
enables directory based extended attributes. This style of extended attribute
imposes no practical limit on either the size or number of attributes which
can be set on a file. Although under Linux the
.Xr getxattr 2
and
.Xr setxattr 2
system calls limit the maximum size to 64K. This is the most compatible
style of extended attribute and is supported by all OpenZFS implementations.
.Pp
System attribute based xattrs can be enabled by setting the value to
.Sy sa .
The key advantage of this type of xattr is improved performance. Storing
extended attributes as system attributes significantly decreases the amount of
disk IO required. Up to 64K of data may be stored per-file in the space
reserved for system attributes. If there is not enough space available for
an extended attribute then it will be automatically written as a directory
based xattr. System attribute based extended attributes are not accessible
on platforms which do not support the
.Sy xattr=sa
feature.
.Pp
The use of system attribute based xattrs is strongly encouraged for users of
SELinux or POSIX ACLs. Both of these features heavily rely on extended
attributes and benefit significantly from the reduced access time.
.Pp
The values
.Sy on
and
.Sy off
are equivalent to the
.Sy xattr
and
.Sy noxattr
mount options.
.It Sy jailed Ns = Ns Cm off | on
Controls whether the dataset is managed from a jail. See the
.Qq Sx Jails
section in
.Xr zfs 8
for more information. Jails are a FreeBSD feature and are not relevant on
other platforms. The default value is
.Cm off .
.It Sy zoned Ns = Ns Sy on Ns | Ns Sy off
Controls whether the dataset is managed from a non-global zone. Zones are a
Solaris feature and are not relevant on other platforms. The default value is
.Sy off .
.El
.Pp
The following three properties cannot be changed after the file system is
created, and therefore, should be set when the file system is created.
If the properties are not set with the
.Nm zfs Cm create
or
.Nm zpool Cm create
commands, these properties are inherited from the parent dataset.
If the parent dataset lacks these properties due to having been created prior to
these features being supported, the new file system will have the default values
for these properties.
.Bl -tag -width ""
.It Xo
.Sy casesensitivity Ns = Ns Sy sensitive Ns | Ns
.Sy insensitive Ns | Ns Sy mixed
.Xc
Indicates whether the file name matching algorithm used by the file system
should be case-sensitive, case-insensitive, or allow a combination of both
styles of matching.
The default value for the
.Sy casesensitivity
property is
.Sy sensitive .
Traditionally,
.Ux
and
.Tn POSIX
file systems have case-sensitive file names.
.Pp
The
.Sy mixed
value for the
.Sy casesensitivity
property indicates that the file system can support requests for both
case-sensitive and case-insensitive matching behavior.
Currently, case-insensitive matching behavior on a file system that supports
mixed behavior is limited to the SMB server product.
For more information about the
.Sy mixed
value behavior, see the "ZFS Administration Guide".
.It Xo
.Sy normalization Ns = Ns Sy none Ns | Ns Sy formC Ns | Ns
.Sy formD Ns | Ns Sy formKC Ns | Ns Sy formKD
.Xc
Indicates whether the file system should perform a
.Sy unicode
normalization of file names whenever two file names are compared, and which
normalization algorithm should be used.
File names are always stored unmodified, names are normalized as part of any
comparison process.
If this property is set to a legal value other than
.Sy none ,
and the
.Sy utf8only
property was left unspecified, the
.Sy utf8only
property is automatically set to
.Sy on .
The default value of the
.Sy normalization
property is
.Sy none .
This property cannot be changed after the file system is created.
.It Sy utf8only Ns = Ns Sy on Ns | Ns Sy off
Indicates whether the file system should reject file names that include
characters that are not present in the
.Sy UTF-8
character code set.
If this property is explicitly set to
.Sy off ,
the normalization property must either not be explicitly set or be set to
.Sy none .
The default value for the
.Sy utf8only
property is
.Sy off .
This property cannot be changed after the file system is created.
.El
.Pp
The
.Sy casesensitivity ,
.Sy normalization ,
and
.Sy utf8only
properties are also new permissions that can be assigned to non-privileged users
by using the ZFS delegated administration feature.
.Ss "Temporary Mount Point Properties"
When a file system is mounted, either through
.Xr mount 8
for legacy mounts or the
.Nm zfs Cm mount
command for normal file systems, its mount options are set according to its
properties.
The correlation between properties and mount options is as follows:
.Bd -literal
PROPERTY MOUNT OPTION
atime atime/noatime
canmount auto/noauto
devices dev/nodev
exec exec/noexec
readonly ro/rw
relatime relatime/norelatime
setuid suid/nosuid
xattr xattr/noxattr
.Ed
.Pp
In addition, these options can be set on a per-mount basis using the
.Fl o
option, without affecting the property that is stored on disk.
The values specified on the command line override the values stored in the
dataset.
The
.Sy nosuid
option is an alias for
.Sy nodevices Ns \&, Ns Sy nosetuid .
These properties are reported as
.Qq temporary
by the
.Nm zfs Cm get
command.
If the properties are changed while the dataset is mounted, the new setting
overrides any temporary settings.
.Ss "User Properties"
In addition to the standard native properties, ZFS supports arbitrary user
properties.
User properties have no effect on ZFS behavior, but applications or
administrators can use them to annotate datasets
.Pq file systems, volumes, and snapshots .
.Pp
User property names must contain a colon
.Pq Qq Sy \&:
character to distinguish them from native properties.
They may contain lowercase letters, numbers, and the following punctuation
characters: colon
.Pq Qq Sy \&: ,
dash
.Pq Qq Sy - ,
period
.Pq Qq Sy \&. ,
and underscore
.Pq Qq Sy _ .
The expected convention is that the property name is divided into two portions
such as
.Em module Ns \&: Ns Em property ,
but this namespace is not enforced by ZFS.
User property names can be at most 256 characters, and cannot begin with a dash
.Pq Qq Sy - .
.Pp
When making programmatic use of user properties, it is strongly suggested to use
a reversed
.Sy DNS
domain name for the
.Em module
component of property names to reduce the chance that two
independently-developed packages use the same property name for different
purposes.
.Pp
The values of user properties are arbitrary strings, are always inherited, and
are never validated.
All of the commands that operate on properties
.Po Nm zfs Cm list ,
.Nm zfs Cm get ,
.Nm zfs Cm set ,
and so forth
.Pc
can be used to manipulate both native properties and user properties.
Use the
.Nm zfs Cm inherit
command to clear a user property.
If the property is not defined in any parent dataset, it is removed entirely.
Property values are limited to 8192 bytes.
|