1 .\" Copyright (c) 2007 The DragonFly Project. All rights reserved.
3 .\" This code is derived from software contributed to The DragonFly Project
4 .\" by Matthew Dillon <dillon@backplane.com>
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38 .Nd HAMMER file system utility
45 .Op Fl C Ar cachesize Ns Op Ns Cm \&: Ns Ar readahead
46 .Op Fl R Ar restrictcmd
47 .Op Fl T Ar restrictpath
49 .Op Fl e Ar scoreboardfile
51 .\" .Op Fl s Ar linkpath
60 This manual page documents the
62 utility which provides miscellaneous functions related to managing a
65 For a general introduction to the
67 file system, its features, and
68 examples on how to set up and maintain one, see
71 The options are as follows:
72 .Bl -tag -width indent
74 Tell the mirror commands to use a 2-way protocol, which allows
75 automatic negotiation of transaction id ranges.
76 This option is automatically enabled by the
80 Make per PFS commands perform on all PFSs if possible.
81 If the command supports this option, it targets all PFSs of the
85 argument (of that command) belongs to.
94 commands support this option.
95 If the command does not support this option, it does nothing.
99 will not attempt to break-up large initial bulk transfers into smaller
101 This can save time but if the link is lost in the middle of the
102 initial bulk transfer you will have to start over from scratch.
103 For more information see the
106 .It Fl b Ar bandwidth
107 Specify a bandwidth limit in bytes per second for mirroring streams.
108 This option is typically used to prevent batch mirroring operations from
109 loading down the machine.
110 The bandwidth may be suffixed with
114 to specify values in kilobytes, megabytes, and gigabytes per second.
115 If no suffix is specified, bytes per second is assumed.
117 Unfortunately this is only applicable to the pre-compression bandwidth
118 when compression is used, so a better solution would probably be to
124 .It Fl C Ar cachesize Ns Op Ns Cm \&: Ns Ar readahead
125 Set the memory cache size for any raw
132 for megabytes is allowed,
133 else the cache size is specified in bytes.
135 The read-behind/read-ahead defaults to 4
139 This option is typically only used with diagnostic commands
140 as kernel-supported commands will use the kernel's buffer cache.
141 .It Fl R Ar restrictcmd
142 This option is used by hammer ssh-remote to restrict the command later
143 on in the argument list. Multiple commands may be specified, separated
144 by a comma (all one argument).
145 .It Fl T Ar restrictpath
146 This option is used by hammer ssh-remote to restrict the filesystem path
147 specified later on in the argument list.
148 .It Fl c Ar cyclefile
149 When pruning, rebalancing or reblocking you can tell the utility
150 to start at the object id stored in the specified file.
151 If the file does not exist
153 will start at the beginning.
156 is told to run for a specific period of time
158 and is unable to complete the operation it will write out
159 the current object id so the next run can pick up where it left off.
162 runs to completion it will delete
164 .It Fl e Ar scoreboardfile
165 Update scoreboard file with progress, primarily used by mirror-stream.
170 will not check that time period has elapsed if this option is given.
172 Specify the volumes making up a
176 is a colon-separated list of devices, each specifying a
182 Specify delay in seconds for
183 .Cm mirror-read-stream .
184 When maintaining a streaming mirroring this option specifies the
185 minimum delay after a batch ends before the next batch is allowed
187 The default is five seconds.
189 Specify the maximum amount of memory
191 will allocate during a dedup pass.
192 Specify a suffix 'm', 'g', or 't' for megabytes, gigabytes, or terabytes.
195 will allocate up to 1G of ram to hold CRC/SHA tables while running dedup.
196 When the limit is reached the dedup code restricts the range of CRCs to
197 keep memory use within bounds and runs multiple passes as necessary until
198 the entire filesystem has been deduped.
205 specification for the source and/or destination.
207 Decrease verboseness.
208 May be specified multiple times.
210 Specify recursion for those commands which support it.
211 .It Fl S Ar splitsize
212 Specify the bulk splitup size in bytes for mirroring streams.
217 will do an initial run-through of the data to calculate good
218 transaction ids to cut up the bulk transfers, creating
219 restart points in case the stream is interrupted.
220 If we don't do this and the stream is interrupted it might
221 have to start all over again.
226 At the moment the run-through is disk-bandwidth-heavy but some
227 future version will limit the run-through to just the B-Tree
228 records and not the record data.
230 The splitsize may be suffixed with
234 to specify values in kilobytes, megabytes, or gigabytes.
235 If no suffix is specified, bytes is assumed.
237 When mirroring very large filesystems the minimum recommended
239 A small split size may wind up generating a great deal of overhead
240 but very little actual incremental data and is not recommended.
242 Specify timeout in seconds.
243 When pruning, rebalancing, reblocking or mirror-reading
244 you can tell the utility to stop after a certain period of time.
245 A value of 0 means unlimited.
246 This option is used along with the
248 option to prune, rebalance or reblock incrementally.
250 Increase verboseness.
251 May be specified multiple times.
253 Enable compression for any remote ssh specifications.
254 This option is typically used with the mirroring directives.
258 for interactive questions.
261 The commands are as follows:
262 .Bl -tag -width indent
263 .\" ==== synctid ====
264 .It Cm synctid Ar filesystem Op Cm quick
265 Generate a guaranteed, formal 64-bit transaction id representing the
266 current state of the specified
269 The file system will be synced to the media.
273 keyword is specified the file system will be soft-synced, meaning that a
274 crash might still undo the state of the file system as of the transaction
275 id returned but any new modifications will occur after the returned
276 transaction id as expected.
278 This operation does not create a snapshot.
279 It is meant to be used
280 to track temporary fine-grained changes to a subset of files and
281 will only remain valid for
283 access purposes for the
285 period configured for the PFS.
286 If you desire a real snapshot then the
288 directive may be what you are looking for.
290 .It Cm bstats Op Ar interval
293 B-Tree statistics until interrupted.
296 seconds between each display.
297 The default interval is one second.
298 .\" ==== iostats ====
299 .It Cm iostats Op Ar interval
303 statistics until interrupted.
306 seconds between each display.
307 The default interval is one second.
309 .It Cm stats Op Ar interval
314 statistics until interrupted.
317 seconds between each display.
318 The default interval is one second.
319 .\" ==== history ====
320 .It Cm history Ns Oo Cm @ Ns Ar offset Ns Oo Cm \&, Ns Ar length Oc Oc Ar path Ns Oo Cm @ Ns Ar offset Ns Oo Cm \&, Ns Ar length Oc Oc Ar ...
321 Show the modification history for inode and data of
326 is given history is shown for data block at given offset,
327 otherwise history is shown for inode.
332 data bytes at given offset are dumped for each version,
337 this directive shows object id and sync status,
338 and for each object version it shows transaction id and time stamp.
339 Files has to exist for this directive to be applicable,
340 to track inodes which has been deleted or renamed see
355 .\" ==== blockmap ====
357 Dump the blockmap for the file system.
360 blockmap is two-layer
361 blockmap representing the maximum possible file system size of 1 Exabyte.
362 Needless to say the second layer is only present for blocks which exist.
364 blockmap represents 8-Megabyte blocks, called big-blocks.
365 Each big-block has an append
366 point, a free byte count, and a typed zone id which allows content to be
367 reverse engineered to some degree.
371 allocations are essentially appended to a selected big-block using
372 the append offset and deducted from the free byte count.
373 When space is freed the free byte count is adjusted but
375 does not track holes in big-blocks for reallocation.
376 A big-block must be completely freed, either
377 through normal file system operations or through reblocking, before
380 Data blocks can be shared by deducting the space used from the free byte
381 count for each shared references.
382 This means the free byte count can legally go negative.
384 This command needs the
387 .\" ==== checkmap ====
389 Check the blockmap allocation count.
391 will scan the freemap, B-Tree, UNDO/REDO FIFO, then collect allocation information,
392 and construct a blockmap in-memory.
393 It will then check that blockmap against the on-disk blockmap.
395 This command needs the
399 .It Cm show Op Ar localization Ns Op Cm \&: Ns Ar object_id Ns Op Cm \&: Ns Ar rec_type Ns Op Cm \&: Ns Ar key Ns Op Cm \&: Ns Ar create_tid
401 By default this command will validate all B-Tree
402 linkages and CRCs, including data CRCs, and will report the most verbose
403 information it can dig up.
404 Any errors will show up with a
406 in column 1 along with various
412 .Ar localization Ns Cm \&: Ns Ar object_id
414 .Ar localization Ns Cm \&: Ns Ar object_id Ns Cm \&: Ns Ar rec_type
416 .Ar localization Ns Cm \&: Ns Ar object_id Ns Cm \&: Ns Ar rec_type Ns Cm \&: Ns Ar key
418 .Ar localization Ns Cm \&: Ns Ar object_id Ns Cm \&: Ns Ar rec_type Ns Cm \&: Ns Ar key Ns Cm \&: Ns Ar create_tid
420 search for the key printing nodes as it recurses down, and then
421 will iterate forwards.
422 These fields are specified in HEX.
423 Note that the PFS id is the top 16 bits of the 32-bit localization
424 field so PFS#1 would be 00010000.
428 the command will report less information about the inode contents.
432 the command will not report the content of the inode or other typed
437 the command will not report volume header information, big-block fill
438 ratios, mirror transaction ids, or report or check data CRCs.
439 B-Tree CRCs and linkages are still checked.
441 This command needs the
444 .\" ==== show-undo ====
448 Dump the UNDO/REDO map.
450 This command needs the
454 .\" Dump the B-Tree, record, large-data, and small-data blockmaps, showing
455 .\" physical block assignments and free space percentages.
456 .\" ==== ssh-remote ====
457 .It Cm ssh-remote Ar command Ar targetdir
458 Used in a ssh authorized_keys line such as
459 command="/sbin/hammer ssh-remote mirror-read /fubarmount" ... to allow
460 mirror-read or mirror-write access to a particular subdirectory tree.
461 This way you do not have to give shell access to the remote box.
463 will obtain the original command line from the SSH_ORIGINAL_COMMAND
464 environment variable, validate it against the restriction, and then
465 re-exec hammer with the validated arguments.
467 The remote hammer command does not allow the
471 options to be passed in.
472 .\" ==== recover ====
473 .It Cm recover Ar targetdir Op Cm full|quick
474 Recover data from a corrupted
477 This is a low level command which operates on the filesystem image and
478 attempts to locate and recover files from a corrupted filesystem.
479 The entire image is scanned linearly looking for B-Tree nodes.
481 found which passes its CRC test is scanned for file, inode, and directory
482 fragments and the target directory is populated with the resulting data.
483 files and directories in the target directory are initially named after
484 the object id and are renamed as fragmentary information is processed.
486 This command keeps track of filename/object_id translations and may eat a
487 considerably amount of memory while operating.
489 This command is literally the last line of defense when it comes to
490 recovering data from a dead filesystem.
494 keyword is specified, this command scans all the big-blocks within the
495 entire image, regardless of whether big-blocks contain active data or meta-data.
496 By default, it linearly scans only up to the last big-block that contains
497 active data or meta-data, if such big-block is detectable.
501 keyword is specified, this command only scans big-blocks that contain
502 B-Tree nodes and associated records, without linearly scanning the entire image.
503 This may speed up the recovery process provided that big-blocks for
504 B-Tree nodes are not corrupted.
506 This command needs the
513 filesystem volume header and other meta-data by overwriting them with irrelevant data.
515 volumes need to be unmounted.
517 This is a fast way to make
519 filesystem unmountable and unrecoverable.
520 After running this command,
522 filesystem data is no longer recoverable using
524 command, although the data still exists within the volumes.
525 As safety measure the
527 flag have no effect on this directive.
529 This command needs the
532 .\" ==== namekey1 ====
533 .It Cm namekey1 Ar filename
536 64-bit directory hash for the specified file name, using
537 the original directory hash algorithm in version 1 of the file system.
538 The low 32 bits are used as an iterator for hash collisions and will be
540 .\" ==== namekey2 ====
541 .It Cm namekey2 Ar filename
544 64-bit directory hash for the specified file name, using
545 the new directory hash algorithm in version 2 of the file system.
546 The low 32 bits are still used as an iterator but will start out containing
547 part of the hash key.
548 .\" ==== namekey32 ====
549 .It Cm namekey32 Ar filename
550 Generate the top 32 bits of a
552 64 bit directory hash for the specified file name.
554 .It Cm info Ar dirpath ...
555 Show extended information about all
557 file systems mounted in the system or the one mounted in
559 when this argument is specified.
561 The information is divided into sections:
562 .Bl -tag -width indent
563 .It Volume identification
564 General information, like the label of the
566 filesystem, the number of volumes it contains, the FSID, and the
569 .It Big-block information
570 Big-block statistics, such as total, used, reserved and free big-blocks.
571 .It Space information
572 Information about space used on the filesystem.
573 Currently total size, used, reserved and free space are displayed.
575 Basic information about the PFSs currently present on a
580 is the ID of the PFS, with 0 being the root PFS.
582 is the current snapshot count on the PFS.
584 displays the mount point of the PFS is currently mounted on (if any).
586 .\" ==== cleanup ====
587 .It Cm cleanup Op Ar filesystem ...
588 This is a meta-command which executes snapshot, prune, rebalance, dedup
589 and reblock commands on the specified
594 is specified this command will clean-up all
596 file systems in use, including PFS's.
597 To do this it will scan all
601 mounts, extract PFS id's, and clean-up each PFS found.
603 This command will access a snapshots
604 directory and a configuration file for each
606 creating them if necessary.
607 .Bl -tag -width indent
608 .It Nm HAMMER No version 2-
609 The configuration file is
611 in the snapshots directory which defaults to
612 .Pa <pfs>/snapshots .
613 .It Nm HAMMER No version 3+
614 The configuration file is saved in file system meta-data, see
617 The snapshots directory defaults to
618 .Pa /var/hammer/<pfs>
619 .Pa ( /var/hammer/root
623 The format of the configuration file is:
624 .Bd -literal -offset indent
625 snapshots <period> <retention-time> [any]
626 prune <period> <max-runtime>
627 rebalance <period> <max-runtime>
628 dedup <period> <max-runtime>
629 reblock <period> <max-runtime>
630 recopy <period> <max-runtime>
634 .Bd -literal -offset indent
635 snapshots 1d 60d # 0d 0d for PFS /tmp, /var/tmp, /usr/obj
638 #dedup 1d 5m # not enabled by default
643 Time is given with a suffix of
649 meaning day, hour, minute and second.
653 directive has a period of 0 and a retention time of 0
654 then snapshot generation is disabled, removal of old snapshots are
655 disabled, and prunes will use
656 .Cm prune-everything .
660 directive has a period of 0 but a non-zero retention time
661 then this command will not create any new snapshots but will remove old
662 snapshots it finds based on the retention time.
664 used on PFS masters where you are generating your own snapshot softlinks
665 manually and on PFS slaves when all you wish to do is prune away existing
666 snapshots inherited via the mirroring stream.
668 By default only snapshots in the form
669 .Ql snap- Ns Ar yyyymmdd Ns Op - Ns Ar HHMM
673 directive is specified as a third argument on the
675 config line then any softlink of the form
676 .Ql *- Ns Ar yyyymmdd Ns Op - Ns Ar HHMM
678 .Ql *. Ns Ar yyyymmdd Ns Op - Ns Ar HHMM
681 A period of 0 for prune, rebalance, dedup, reblock or recopy disables the directive.
682 A max-runtime of 0 means unlimited.
684 If period hasn't passed since the previous
687 For example a day has passed when midnight is passed (localtime).
690 flag is given the period is ignored.
698 The default configuration file will create a daily snapshot, do a daily
699 pruning, rebalancing, deduping and reblocking run and a monthly recopy run.
700 Reblocking is defragmentation with a level of 95%,
701 and recopy is full defragmentation.
703 By default prune, dedup and rebalance operations are time limited to 5 minutes,
704 and reblock operations to a bit over 5 minutes,
705 and recopy operations to a bit over 10 minutes.
706 Reblocking and recopy runs are each broken down into four separate functions:
707 B-Tree, inodes, dirs and data.
708 Each function is time limited to the time given in the configuration file,
709 but the B-Tree, inodes and dirs functions usually does not take very long time,
710 full defragmentation is always used for these three functions.
711 Also note that this directive will by default disable snapshots on
718 The defaults may be adjusted by modifying the configuration file.
719 The pruning and reblocking commands automatically maintain a cyclefile
720 for incremental operation.
721 If you interrupt (^C) the program the cyclefile will be updated,
723 may continue to run in the background for a few seconds until the
725 ioctl detects the interrupt.
728 PFS option can be set to use another location for the snapshots directory.
730 Work on this command is still in progress.
732 An ability to remove snapshots dynamically as the
733 file system becomes full.
734 .\" ==== abort-cleanup ====
736 This command will terminate all active
740 .It Cm config Op Ar filesystem Op Ar configfile
743 Show or change configuration for
745 If zero or one arguments are specified this function dumps the current
746 configuration file to stdout.
747 Zero arguments specifies the PFS containing the current directory.
748 This configuration file is stored in file system meta-data.
749 If two arguments are specified this function installs a new configuration file
754 versions less than 3 the configuration file is by default stored in
755 .Pa <pfs>/snapshots/config ,
756 but in all later versions the configuration file is stored in file system
758 .\" ==== viconfig ====
759 .It Cm viconfig Op Ar filesystem
762 Edit the configuration file and reinstall into file system meta-data when done.
763 Zero arguments specifies the PFS containing the current directory.
764 .\" ==== volume-add ====
765 .It Cm volume-add Ar device Ar filesystem
772 and add all of its space to
776 file system can use up to 256 volumes.
779 All existing data contained on
781 will be destroyed by this operation!
786 file system, formatting will be denied.
787 You can overcome this sanity check by using
789 to erase the beginning sectors of the device.
791 Remember that you have to specify
793 together with any other device that make up the file system,
800 is root file system, also remember to add
803 .Va vfs.root.mountfrom
805 .Pa /boot/loader.conf ,
808 .\" ==== volume-del ====
809 .It Cm volume-del Ar device Ar filesystem
815 Remember that you have to remove
817 from the colon-separated list in
823 is root file system, also remember to remove
826 .Va vfs.root.mountfrom
828 .Pa /boot/loader.conf ,
832 It is not possible to remove the
838 layer1 blockmap and UNDO/REDO FIFO.
842 filesystem before it attempts to remove the volume if the volume is not empty.
843 .\" ==== volume-list ====
844 .It Cm volume-list Ar filesystem
845 List the volumes that make up
847 If -v is specified the command shows volume number for each volume as well as
850 .\" ==== volume-blkdevs ====
851 .It Cm volume-blkdevs Ar filesystem
852 List the volumes that make up
857 .\" ==== snapshot ====
858 .It Cm snapshot Oo Ar filesystem Oc Ar snapshot-dir
859 .It Cm snapshot Ar filesystem Ar snapshot-dir Op Ar note
860 Take a snapshot of the file system either explicitly given by
862 or implicitly derived from the
864 argument and creates a symlink in the directory provided by
866 pointing to the snapshot.
869 is not a directory, it is assumed to be a format string passed to
871 with the current time as parameter.
874 refers to an existing directory, a default format string of
876 is assumed and used as name for the newly created symlink.
878 Snapshot is a per PFS operation, so each PFS in a
880 file system have to be snapshot separately.
882 Example, assuming that
890 are file systems on their own, the following invocations:
891 .Bd -literal -offset indent
892 hammer snapshot /mysnapshots
894 hammer snapshot /mysnapshots/%Y-%m-%d
896 hammer snapshot /obj /mysnapshots/obj-%Y-%m-%d
898 hammer snapshot /usr /my/snaps/usr "note"
901 Would create symlinks similar to:
902 .Bd -literal -offset indent
903 /mysnapshots/snap-20080627-1210 -> /@@0x10d2cd05b7270d16
905 /mysnapshots/2008-06-27 -> /@@0x10d2cd05b7270d16
907 /mysnapshots/obj-2008-06-27 -> /obj@@0x10d2cd05b7270d16
909 /my/snaps/usr/snap-20080627-1210 -> /usr@@0x10d2cd05b7270d16
914 version 3+ file system the snapshot is also recorded in file system meta-data
915 along with the optional
921 .It Cm snap Ar path Op Ar note
924 Create a snapshot for the PFS containing
926 and create a snapshot softlink.
927 If the path specified is a
928 directory a standard snapshot softlink will be created in the directory.
929 The snapshot softlink points to the base of the mounted PFS.
930 .It Cm snaplo Ar path Op Ar note
933 Create a snapshot for the PFS containing
935 and create a snapshot softlink.
936 If the path specified is a
937 directory a standard snapshot softlink will be created in the directory.
938 The snapshot softlink points into the directory it is contained in.
939 .It Cm snapq Ar dir Op Ar note
942 Create a snapshot for the PFS containing the specified directory but do
943 not create a softlink.
944 Instead output a path which can be used to access
945 the directory via the snapshot.
947 An absolute or relative path may be specified.
948 The path will be used as-is as a prefix in the path output to stdout.
950 snap and snapshot directives the snapshot transaction id will be registered
951 in the file system meta-data.
952 .It Cm snaprm Ar path Ar ...
953 .It Cm snaprm Ar transaction_id Ar ...
954 .It Cm snaprm Ar filesystem Ar transaction_id Ar ...
957 Remove a snapshot given its softlink or transaction id.
958 If specifying a transaction id
959 the snapshot is removed from file system meta-data but you are responsible
960 for removing any related softlinks.
962 If a softlink path is specified the filesystem and transaction id
963 is derived from the contents of the softlink.
964 If just a transaction id is specified it is assumed to be a snapshot in the
966 filesystem you are currently chdir'd into.
967 You can also specify the filesystem and transaction id explicitly.
968 .It Cm snapls Op Ar path ...
971 Dump the snapshot meta-data for PFSs containing each
973 listing all available snapshots and their notes.
974 If no arguments are specified snapshots for the PFS containing the
975 current directory are listed.
976 This is the definitive list of snapshots for the file system.
978 .It Cm prune Ar softlink-dir
979 Prune the file system based on previously created snapshot softlinks.
980 Pruning is the act of deleting file system history.
983 command will delete file system history such that
984 the file system state is retained for the given snapshots,
985 and all history after the latest snapshot.
986 By setting the per PFS parameter
988 history is guaranteed to be saved at least this time interval.
989 All other history is deleted.
991 The target directory is expected to contain softlinks pointing to
992 snapshots of the file systems you wish to retain.
993 The directory is scanned non-recursively and the mount points and
994 transaction ids stored in the softlinks are extracted and sorted.
995 The file system is then explicitly pruned according to what is found.
996 Cleaning out portions of the file system is as simple as removing a
997 snapshot softlink and then running the
1001 As a safety measure pruning only occurs if one or more softlinks are found
1004 snapshot id extension.
1005 Currently the scanned softlink directory must contain softlinks pointing
1009 The softlinks may specify absolute or relative paths.
1010 Softlinks must use 20-character
1012 transaction ids, as might be returned from
1013 .Nm Cm synctid Ar filesystem .
1015 Pruning is a per PFS operation, so each PFS in a
1017 file system have to be pruned separately.
1019 Note that pruning a file system may not immediately free-up space,
1020 though typically some space will be freed if a large number of records are
1022 The file system must be reblocked to completely recover all available space.
1024 Example, lets say your that you didn't set
1026 and snapshot directory contains the following links:
1027 .Bd -literal -offset indent
1028 lrwxr-xr-x 1 root wheel 29 May 31 17:57 snap1 ->
1029 /usr/obj/@@0x10d2cd05b7270d16
1031 lrwxr-xr-x 1 root wheel 29 May 31 17:58 snap2 ->
1032 /usr/obj/@@0x10d2cd13f3fde98f
1034 lrwxr-xr-x 1 root wheel 29 May 31 17:59 snap3 ->
1035 /usr/obj/@@0x10d2cd222adee364
1038 If you were to run the
1040 command on this directory, then the
1043 mount will be pruned to retain the above three snapshots.
1044 In addition, history for modifications made to the file system older than
1045 the oldest snapshot will be destroyed and history for potentially fine-grained
1046 modifications made to the file system more recently than the most recent
1047 snapshot will be retained.
1049 If you then delete the
1051 softlink and rerun the
1054 history for modifications pertaining to that snapshot would be destroyed.
1058 file system versions 3+ this command also scans the snapshots stored
1059 in the file system meta-data and includes them in the prune.
1060 .\" ==== prune-everything ====
1061 .It Cm prune-everything Ar filesystem
1062 Remove all historical records from
1064 Use this directive with caution on PFSs where you intend to use history.
1066 This command does not remove snapshot softlinks but will delete all
1067 snapshots recorded in file system meta-data (for file system version 3+).
1068 The user is responsible for deleting any softlinks.
1070 Pruning is a per PFS operation, so each PFS in a
1072 file system have to be pruned separately.
1073 .\" ==== rebalance ====
1074 .It Cm rebalance Ar filesystem Op Ar saturation_percentage
1075 Rebalance the B-Tree, nodes with small number of
1076 elements will be combined and element counts will be smoothed out
1079 The saturation percentage is between 50% and 100%.
1080 The default is 85% (the
1082 suffix is not needed).
1084 Rebalancing is a per PFS operation, so each PFS in a
1086 file system have to be rebalanced separately.
1088 .It Cm dedup Ar filesystem
1091 Perform offline (post-process) deduplication.
1092 Deduplication occurs at
1093 the block level, currently only data blocks of the same size can be
1094 deduped, metadata blocks can not.
1095 The hash function used for comparing
1096 data blocks is CRC-32 (CRCs are computed anyways as part of
1098 data integrity features, so there's no additional overhead).
1099 Since CRC is a weak hash function a byte-by-byte comparison is done
1100 before actual deduping.
1101 In case of a CRC collision (two data blocks have the same CRC
1102 but different contents) the checksum is upgraded to SHA-256.
1106 reblocker may partially blow up (re-expand) dedup (reblocker's normal
1107 operation is to reallocate every record, so it's possible for deduped
1108 blocks to be re-expanded back).
1110 Deduplication is a per PFS operation, so each PFS in a
1112 file system have to be deduped separately.
1114 means that if you have duplicated data in two different PFSs that data
1115 won't be deduped, however the addition of such feature is planned.
1119 option should be used to limit memory use during the dedup run if the
1120 default 1G limit is too much for the machine.
1121 .\" ==== dedup-simulate ====
1122 .It Cm dedup-simulate Ar filesystem
1123 Shows potential space savings (simulated dedup ratio) one can get after
1127 If the estimated dedup ratio is greater than 1.00 you will see
1128 dedup space savings.
1129 Remember that this is an estimated number, in
1130 practice real dedup ratio will be slightly smaller because of
1132 big-block underflows, B-Tree locking issues and other factors.
1134 Note that deduplication currently works only on bulk data so if you
1139 commands on a PFS that contains metadata only (directory entries,
1140 softlinks) you will get a 0.00 dedup ratio.
1144 option should be used to limit memory use during the dedup run if the
1145 default 1G limit is too much for the machine.
1146 .\" ==== reblock* ====
1147 .It Cm reblock Ar filesystem Op Ar fill_percentage
1148 .It Cm reblock-btree Ar filesystem Op Ar fill_percentage
1149 .It Cm reblock-inodes Ar filesystem Op Ar fill_percentage
1150 .It Cm reblock-dirs Ar filesystem Op Ar fill_percentage
1151 .It Cm reblock-data Ar filesystem Op Ar fill_percentage
1152 Attempt to defragment and free space for reuse by reblocking a live
1155 Big-blocks cannot be reused by
1157 until they are completely free.
1158 This command also has the effect of reordering all elements, effectively
1159 defragmenting the file system.
1161 The default fill percentage is 100% and will cause the file system to be
1162 completely defragmented.
1163 All specified element types will be reallocated and rewritten.
1164 If you wish to quickly free up space instead try specifying
1165 a smaller fill percentage, such as 90% or 80% (the
1167 suffix is not needed).
1169 Since this command may rewrite the entire contents of the disk it is
1170 best to do it incrementally from a
1176 options to limit the run time.
1177 The file system would thus be defragmented over long period of time.
1179 It is recommended that separate invocations be used for each data type.
1180 B-Tree nodes, inodes, and directories are typically the most important
1181 elements needing defragmentation.
1182 Data can be defragmented over a longer period of time.
1184 Reblocking is a per PFS operation, so each PFS in a
1186 file system have to be reblocked separately.
1187 .\" ==== pfs-status ====
1188 .It Cm pfs-status Ar dirpath ...
1189 Retrieve the mirroring configuration parameters for the specified
1191 file systems or pseudo-filesystems (PFS's).
1192 .\" ==== pfs-master ====
1193 .It Cm pfs-master Ar dirpath Op Ar options
1194 Create a pseudo-filesystem (PFS) inside a
1197 Up to 65536 PFSs can be created.
1198 Each PFS uses an independent inode numbering space making it suitable
1203 directive creates a PFS that you can read, write, and use as a mirroring
1206 A PFS can only be truly destroyed with the
1209 Removing the softlink will not destroy the underlying PFS.
1211 A PFS can only be created in the root PFS,
1212 not in a PFS created by
1217 It is recommended that
1223 directory at root of
1227 It is recommended to use a
1229 mount to access a PFS, except for root PFS, for more information see
1231 .\" ==== pfs-slave ====
1232 .It Cm pfs-slave Ar dirpath Op Ar options
1233 Create a pseudo-filesystem (PFS) inside a
1236 Up to 65536 PFSs can be created.
1237 Each PFS uses an independent inode numbering space making it suitable
1242 directive creates a PFS that you can use as a mirroring source or target.
1243 You will not be able to access a slave PFS until you have completed the
1244 first mirroring operation with it as the target (its root directory will
1245 not exist until then).
1247 Access to the pfs-slave via the special softlink, as described in the
1248 .Sx PSEUDO-FILESYSTEM (PFS) NOTES
1252 dynamically modify the snapshot transaction id by returning a dynamic result
1257 A PFS can only be truly destroyed with the
1260 Removing the softlink will not destroy the underlying PFS.
1262 A PFS can only be created in the root PFS,
1263 not in a PFS created by
1268 It is recommended that
1274 directory at root of
1278 It is recommended to use a
1280 mount to access a PFS, except for root PFS, for more information see
1282 .\" ==== pfs-update ====
1283 .It Cm pfs-update Ar dirpath Op Ar options
1284 Update the configuration parameters for an existing
1286 file system or pseudo-filesystem.
1287 Options that may be specified:
1288 .Bl -tag -width indent
1289 .It Cm sync-beg-tid= Ns Ar 0x16llx
1290 This is the automatic snapshot access starting transaction id for
1292 This parameter is normally updated automatically by the
1296 It is important to note that accessing a mirroring slave
1297 with a transaction id greater than the last fully synchronized transaction
1298 id can result in an unreliable snapshot since you will be accessing
1299 data that is still undergoing synchronization.
1301 Manually modifying this field is dangerous and can result in a broken mirror.
1302 .It Cm sync-end-tid= Ns Ar 0x16llx
1303 This is the current synchronization point for mirroring slaves.
1304 This parameter is normally updated automatically by the
1308 Manually modifying this field is dangerous and can result in a broken mirror.
1309 .It Cm shared-uuid= Ns Ar uuid
1310 Set the shared UUID for this file system.
1311 All mirrors must have the same shared UUID.
1312 For safety purposes the
1314 directives will refuse to operate on a target with a different shared UUID.
1316 Changing the shared UUID on an existing, non-empty mirroring target,
1317 including an empty but not completely pruned target,
1318 can lead to corruption of the mirroring target.
1319 .It Cm unique-uuid= Ns Ar uuid
1320 Set the unique UUID for this file system.
1321 This UUID should not be used anywhere else,
1322 even on exact copies of the file system.
1323 .It Cm label= Ns Ar string
1324 Set a descriptive label for this file system.
1325 .It Cm snapshots= Ns Ar string
1326 Specify the snapshots directory which
1329 will use to manage this PFS.
1330 .Bl -tag -width indent
1331 .It Nm HAMMER No version 2-
1332 The snapshots directory does not need to be configured for
1333 PFS masters and will default to
1334 .Pa <pfs>/snapshots .
1336 PFS slaves are mirroring slaves so you cannot configure a snapshots
1337 directory on the slave itself to be managed by the slave's machine.
1338 In fact, the slave will likely have a
1340 sub-directory mirrored
1341 from the master, but that directory contains the configuration the master
1342 is using for its copy of the file system, not the configuration that we
1343 want to use for our slave.
1345 It is recommended that
1346 .Pa <fs>/var/slaves/<name>
1347 be configured for a PFS slave, where
1353 is an appropriate label.
1354 .It Nm HAMMER No version 3+
1355 The snapshots directory does not need to be configured for PFS masters or
1357 The snapshots directory defaults to
1358 .Pa /var/hammer/<pfs>
1359 .Pa ( /var/hammer/root
1363 You can control snapshot retention on your slave independent of the master.
1364 .It Cm snapshots-clear
1367 directory path for this PFS.
1368 .It Cm prune-min= Ns Ar N Ns Cm d
1369 .It Cm prune-min= Ns Oo Ar N Ns Cm d/ Oc Ns \
1370 Ar hh Ns Op Cm \&: Ns Ar mm Ns Op Cm \&: Ns Ar ss
1371 Set the minimum fine-grained data retention period.
1373 always retains fine-grained history up to the most recent snapshot.
1374 You can extend the retention period further by specifying a non-zero
1376 Any snapshot softlinks within the retention period are ignored
1377 for the purposes of pruning (i.e.\& the fine grained history is retained).
1378 Number of days, hours, minutes and seconds are given as
1383 Because the transaction id in the snapshot softlink cannot be used
1384 to calculate a timestamp,
1386 uses the earlier of the
1390 field of the softlink to
1391 determine which snapshots fall within the retention period.
1392 Users must be sure to retain one of these two fields when manipulating
1395 .\" ==== pfs-upgrade ====
1396 .It Cm pfs-upgrade Ar dirpath
1397 Upgrade a PFS from slave to master operation.
1398 The PFS will be rolled back to the current end synchronization transaction id
1399 (removing any partial synchronizations), and will then become writable.
1403 currently supports only single masters and using
1404 this command can easily result in file system corruption
1405 if you don't know what you are doing.
1407 This directive will refuse to run if any programs have open descriptors
1408 in the PFS, including programs chdir'd into the PFS.
1409 .\" ==== pfs-downgrade ====
1410 .It Cm pfs-downgrade Ar dirpath
1411 Downgrade a master PFS from master to slave operation.
1412 The PFS becomes read-only and access will be locked to its
1415 This directive will refuse to run if any programs have open descriptors
1416 in the PFS, including programs chdir'd into the PFS.
1417 .\" ==== pfs-destroy ====
1418 .It Cm pfs-destroy Ar dirpath
1419 This permanently destroys a PFS.
1421 This directive will refuse to run if any programs have open descriptors
1422 in the PFS, including programs chdir'd into the PFS.
1423 As safety measure the
1425 flag have no effect on this directive.
1426 .\" ==== mirror-read ====
1427 .It Cm mirror-read Ar filesystem Op Ar begin-tid
1428 Generate a mirroring stream to stdout.
1429 The stream ends when the transaction id space has been exhausted.
1431 may be a master or slave PFS.
1432 .\" ==== mirror-read-stream ====
1433 .It Cm mirror-read-stream Ar filesystem Op Ar begin-tid
1434 Generate a mirroring stream to stdout.
1435 Upon completion the stream is paused until new data is synced to the
1438 Operation continues until the pipe is broken.
1441 command for more details.
1442 .\" ==== mirror-write ====
1443 .It Cm mirror-write Ar filesystem
1444 Take a mirroring stream on stdin.
1446 must be a slave PFS.
1448 This command will fail if the
1450 configuration field for the two file systems do not match.
1453 command for more details.
1455 If the target PFS does not exist this command will ask you whether
1456 you want to create a compatible PFS slave for the target or not.
1457 .\" ==== mirror-dump ====
1458 .It Ar mirror-dump Ar [header]
1463 to dump an ASCII representation of the mirroring stream.
1466 is specified, only the header information is shown.
1467 .\" ==== mirror-copy ====
1468 .\".It Cm mirror-copy Ar [[user@]host:]filesystem [[user@]host:]filesystem
1469 .It Cm mirror-copy \
1470 Oo Oo Ar user Ns Cm @ Oc Ns Ar host Ns Cm \&: Oc Ns Ar filesystem \
1471 Oo Oo Ar user Ns Cm @ Oc Ns Ar host Ns Cm \&: Oc Ns Ar filesystem
1472 This is a shortcut which pipes a
1477 If a remote host specification is made the program forks a
1479 (or other program as specified by the
1481 environment variable) and execs the
1485 on the appropriate host.
1486 The source may be a master or slave PFS, and the target must be a slave PFS.
1488 This command also establishes full duplex communication and turns on
1489 the 2-way protocol feature
1491 which automatically negotiates transaction id
1492 ranges without having to use a cyclefile.
1493 If the operation completes successfully the target PFS's
1496 Note that you must re-chdir into the target PFS to see the updated information.
1497 If you do not you will still be in the previous snapshot.
1499 If the target PFS does not exist this command will ask you whether
1500 you want to create a compatible PFS slave for the target or not.
1501 .\" ==== mirror-stream ====
1502 .\".It Cm mirror-stream Ar [[user@]host:]filesystem [[user@]host:]filesystem
1503 .It Cm mirror-stream \
1504 Oo Oo Ar user Ns Cm @ Oc Ns Ar host Ns Cm \&: Oc Ns Ar filesystem \
1505 Oo Oo Ar user Ns Cm @ Oc Ns Ar host Ns Cm \&: Oc Ns Ar filesystem
1506 This is a shortcut which pipes a
1507 .Cm mirror-read-stream
1511 This command works similarly to
1513 but does not exit after the initial mirroring completes.
1514 The mirroring operation will resume as changes continue to be made to the
1516 The command is commonly used with
1520 options to keep the mirroring target in sync with the source on a continuing
1523 If the pipe is broken the command will automatically retry after sleeping
1525 The time slept will be 15 seconds plus the time given in the
1529 This command also detects the initial-mirroring case and spends some
1530 time scanning the B-Tree to find good break points, allowing the initial
1531 bulk mirroring operation to be broken down into 4GB pieces.
1532 This means that the user can kill and restart the operation and it will
1533 not have to start from scratch once it has gotten past the first chunk.
1536 option may be used to change the size of pieces and the
1538 option may be used to disable this feature and perform an initial bulk
1540 .\" ==== version ====
1541 .It Cm version Ar filesystem
1542 This command returns the
1544 file system version for the specified
1546 as well as the range of versions supported in the kernel.
1549 option may be used to remove the summary at the end.
1550 .\" ==== version-upgrade ====
1551 .It Cm version-upgrade Ar filesystem Ar version Op Cm force
1557 Once upgraded a file system may not be downgraded.
1558 If you wish to upgrade a file system to a version greater or equal to the
1559 work-in-progress (WIP) version number you must specify the
1562 Use of WIP versions should be relegated to testing and may require wiping
1563 the file system as development progresses, even though the WIP version might
1567 This command operates on the entire
1569 file system and is not a per PFS operation.
1570 All PFS's will be affected.
1571 .Bl -tag -width indent
1574 default version, first
1579 New directory entry layout.
1580 This version is using a new directory hash key.
1583 New snapshot management, using file system meta-data for saving
1584 configuration file and snapshots (transaction ids etc.).
1585 Also default snapshots directory has changed.
1589 New undo/redo/flush, giving
1591 a much faster sync and fsync.
1594 Deduplication support.
1597 Directory hash ALG1.
1598 Tends to maintain inode number / directory name entry ordering better
1599 for files after minor renaming.
1602 Use the ISCSI crc32 algorithm instead of our custom polynomial. This makes
1603 it easier to use faster cpu implementation of the crc algorithm. CPU
1604 overhead is reduced but performance is unlikely to be impacted a whole lot.
1607 .Sh PSEUDO-FILESYSTEM (PFS) NOTES
1608 The root of a PFS is not hooked into the primary
1610 file system as a directory.
1613 creates a special softlink called
1615 (exactly 10 characters long) in the primary
1619 then modifies the contents of the softlink as read by
1621 and thus what you see with an
1623 command or if you were to
1626 If the PFS is a master the link reflects the current state of the PFS.
1627 If the PFS is a slave the link reflects the last completed snapshot, and the
1628 contents of the link will change when the next snapshot is completed, and
1633 utility employs numerous safeties to reduce user foot-shooting.
1636 directive requires that the target be configured as a slave and that the
1638 field of the mirroring source and target match.
1643 directives require that the PFS softlink be created under the main
1645 filesystem mount. You may only access PFS softlinks via the main
1648 .Sh DOUBLE_BUFFER MODE
1649 There is a limit to the number of vnodes the kernel can cache, and because
1650 file buffers are associated with a vnode the related data cache can get
1651 blown away when operating on large numbers of files even if the system has
1652 sufficient memory to hold the file data.
1656 double buffer mode by setting the
1659 .Va vfs.hammer.double_buffer
1662 will cache file data via the block device and copy it into the per-file
1663 buffers as needed. The data will be double-cached at least until the
1664 buffer cache throws away the file buffer.
1665 This mode is typically used in conjunction with
1668 .Va vm.swapcache.data_enable
1669 is turned on in order to prevent unnecessary re-caching of file data
1670 due to vnode recycling.
1671 The swapcache will save the cached VM pages related to
1674 device (which doesn't recycle unless you umount the filesystem) instead
1675 of the cached VM pages backing the file vnodes.
1677 Double buffering is normally desirable when working with large filesystems,
1678 particularly when swapcache is used.
1679 The swapcache can only back active VM objects, including the block device,
1680 and large filesystems often have far more inodes than the kernel can support.
1681 In addition, when using this mode, you may wish to reduce the
1683 setting for the system to force the system to do less caching of logical
1684 file buffers and more caching of device buffers, since the device buffers
1685 are backing the logical file buffers.
1686 .Sh UPGRADE INSTRUCTIONS HAMMER V1 TO V2
1687 This upgrade changes the way directory entries are stored.
1688 It is possible to upgrade a V1 file system to V2 in place, but
1689 directories created prior to the upgrade will continue to use
1692 Note that the slave mirroring code in the target kernel had bugs in
1693 V1 which can create an incompatible root directory on the slave.
1696 master created after the upgrade with a
1698 slave created prior to the upgrade.
1700 Any directories created after upgrading will use a new layout.
1701 .Sh UPGRADE INSTRUCTIONS HAMMER V2 TO V3
1702 This upgrade adds meta-data elements to the B-Tree.
1703 It is possible to upgrade a V2 file system to V3 in place.
1704 After issuing the upgrade be sure to run a
1707 to perform post-upgrade tasks.
1709 After making this upgrade running a
1714 directory for each PFS mount into
1715 .Pa /var/hammer/<pfs> .
1718 root mount will migrate
1721 .Pa /var/hammer/root .
1722 Migration occurs only once and only if you have not specified
1723 a snapshots directory in the PFS configuration.
1724 If you have specified a snapshots directory in the PFS configuration no
1725 automatic migration will occur.
1727 For slaves, if you desire, you can migrate your snapshots
1728 config to the new location manually and then clear the
1729 snapshot directory configuration in the slave PFS.
1730 The new snapshots hierarchy is designed to work with
1731 both master and slave PFSs equally well.
1733 In addition, the old config file will be moved to file system meta-data,
1734 editable via the new
1738 The old config file will be deleted.
1739 Migration occurs only once.
1741 The V3 file system has new
1743 directives for creating snapshots.
1744 All snapshot directives, including the original, will create
1745 meta-data entries for the snapshots and the pruning code will
1746 automatically incorporate these entries into its list and
1747 expire them the same way it expires softlinks.
1748 If you by accident blow away your snapshot softlinks you can use the
1750 directive to get a definitive list from the file system meta-data and
1751 regenerate them from that list.
1756 to backup file systems your scripts may be using the
1758 directive to generate transaction ids.
1759 This directive does not create a snapshot.
1760 You will have to modify your scripts to use the
1762 directive to generate the linkbuf for the softlink you create, or
1763 use one of the other
1768 directive will continue to work as expected and in V3 it will also
1769 record the snapshot transaction id in file system meta-data.
1770 You may also want to make use of the new
1772 tag for the meta-data.
1775 If you used to remove snapshot softlinks with
1777 you should probably start using the
1779 directive instead to also remove the related meta-data.
1780 The pruning code scans the meta-data so just removing the
1781 softlink is not sufficient.
1782 .Sh UPGRADE INSTRUCTIONS HAMMER V3 TO V4
1783 This upgrade changes undo/flush, giving faster sync.
1784 It is possible to upgrade a V3 file system to V4 in place.
1785 This upgrade reformats the UNDO/REDO FIFO (typically 1GB),
1786 so upgrade might take a minute or two depending.
1788 Version 4 allows the UNDO/REDO FIFO to be flushed without also having
1789 to flush the volume header, removing 2 of the 4 disk syncs typically
1792 and removing 1 of the 2 disk syncs typically
1793 required for a flush sequence.
1794 Version 4 also implements the REDO log (see
1795 .Sx FSYNC FLUSH MODES
1796 below) which is capable
1797 of fsync()ing with either one disk flush or zero disk flushes.
1798 .Sh UPGRADE INSTRUCTIONS HAMMER V4 TO V5
1799 This upgrade brings in deduplication support.
1800 It is possible to upgrade a V4 file system to V5 in place.
1801 Technically it makes the layer2
1803 field a signed value instead of unsigned, allowing it to go negative.
1804 A version 5 filesystem is required for dedup operation.
1805 .Sh UPGRADE INSTRUCTIONS HAMMER V5 TO V6
1806 It is possible to upgrade a V5 file system to V6 in place.
1807 .Sh UPGRADE INSTRUCTIONS HAMMER V6 TO V7
1808 It is possible to upgrade a V6 file system to V7 in place.
1809 After upgrading any new files will use the new, faster CRC.
1810 You can convert all existing files to use the new CRC by issuing
1811 a full reblock via 'hammer reblock <fs>'.
1812 You only have to do this once.
1813 .Sh FSYNC FLUSH MODES
1815 implements five different fsync flush modes via the
1816 .Va vfs.hammer.fsync_mode
1819 version 4+ file systems.
1823 fsync mode 3 is set by default.
1824 REDO operation and recovery is enabled by default.
1825 .Bl -tag -width indent
1827 Full synchronous fsync semantics without REDO.
1830 will not generate REDOs.
1833 will completely sync
1834 the data and meta-data and double-flush the FIFO, including
1835 issuing two disk synchronization commands.
1836 The data is guaranteed
1837 to be on the media as of when
1840 Needless to say, this is slow.
1842 Relaxed asynchronous fsync semantics without REDO.
1844 This mode works the same as mode 0 except the last disk synchronization
1845 command is not issued.
1846 It is faster than mode 0 but not even remotely
1847 close to the speed you get with mode 2 or mode 3.
1849 Note that there is no chance of meta-data corruption when using this
1850 mode, it simply means that the data you wrote and then
1852 might not have made it to the media if the storage system crashes at a bad
1855 Full synchronous fsync semantics using REDO.
1856 NOTE: If not running a
1858 version 4 filesystem or later mode 0 is silently used.
1861 will generate REDOs in the UNDO/REDO FIFO based on a heuristic.
1862 If this is sufficient to satisfy the
1864 operation the blocks will be written out and
1866 will wait for the I/Os to complete,
1867 and then followup with a disk sync command to guarantee the data
1868 is on the media before returning.
1869 This is slower than mode 3 and can result in significant disk or
1870 SSDs overheads, though not as bad as mode 0 or mode 1.
1872 Relaxed asynchronous fsync semantics using REDO.
1873 NOTE: If not running a
1875 version 4 filesystem or later mode 1 is silently used.
1878 will generate REDOs in the UNDO/REDO FIFO based on a heuristic.
1879 If this is sufficient to satisfy the
1881 operation the blocks
1882 will be written out and
1884 will wait for the I/Os to complete,
1887 issue a disk synchronization command.
1889 Note that there is no chance of meta-data corruption when using this
1890 mode, it simply means that the data you wrote and then
1893 not have made it to the media if the storage system crashes at a bad
1896 This mode is the fastest production fsyncing mode available.
1897 This mode is equivalent to how the UFS fsync in the
1906 This mode is primarily designed
1907 for testing and should not be used on a production system.
1909 .Sh RESTORING FROM A SNAPSHOT BACKUP
1910 You restore a snapshot by copying it over to live, but there is a caveat.
1911 The mtime and atime fields for files accessed via a snapshot is locked
1912 to the ctime in order to keep the snapshot consistent, because neither
1913 mtime nor atime changes roll any history.
1915 In order to avoid unnecessary copying it is recommended that you use
1919 when doing the copyback.
1920 Also make sure you traverse the snapshot softlink by appending a ".",
1921 as in "<snapshotpath>/.", and you match up the directory properly.
1922 .Sh RESTORING A PFS FROM A MIRROR
1923 A PFS can be restored from a mirror with
1926 data must be copied separately.
1927 At last the PFS can be upgraded to master using
1930 It is not possible to restore the root PFS by using mirroring,
1931 as the root PFS is always a master PFS.
1932 A normal copy (e.g.\& using
1934 must be done, ignoring history.
1935 If history is important, old root PFS can me restored to a new PFS, and
1936 important directories/files can be
1938 mounted to the new PFS.
1940 The following environment variables affect the execution of
1942 .Bl -tag -width ".Ev EDITOR"
1944 The editor program specified in the variable
1946 will be invoked instead of the default editor, which is
1949 The command specified in the variable
1951 will be used to initiate remote operations for the mirror-copy and
1952 mirror-stream commands instead of the default command, which is
1954 The program will be invoked via
1959 .Cm -l user host <remote-command>
1967 .Bl -tag -width ".It Pa <fs>/var/slaves/<name>" -compact
1968 .It Pa <pfs>/snapshots
1969 default per PFS snapshots directory
1972 .It Pa /var/hammer/<pfs>
1973 default per PFS snapshots directory (not root)
1976 .It Pa /var/hammer/root
1977 default snapshots directory for root directory
1980 .It Pa <snapshots>/config
1987 .It Pa <fs>/var/slaves/<name>
1988 recommended slave PFS snapshots directory
1992 recommended PFS directory
2000 .Xr periodic.conf 5 ,
2002 .Xr mount_hammer 8 ,
2004 .Xr newfs_hammer 8 ,
2010 utility first appeared in
2013 .An Matthew Dillon Aq Mt dillon@backplane.com
projects / dragonfly.git / blob