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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33 .\" $DragonFly: src/sbin/hammer/hammer.8,v 1.58 2008/11/13 02:04:27 dillon Exp $
35 .Dd September 20, 2009
40 .Nd HAMMER file system utility
46 .Op Fl f Ar blkdev[:blkdev]*
47 .\" .Op Fl s Ar linkpath
50 .Op Fl C Ar cachesize[:readahead]
54 This manual page documents the
56 utility which provides miscellaneous functions related to managing a
59 For a general introduction to the
61 file system, its features, and
62 examples on how to set up and maintain one, see
65 The options are as follows:
66 .Bl -tag -width indent
70 Tell the mirror commands to use a 2-way protocol, which allows
71 automatic negotiation of transaction id ranges.
72 This option is automatically enabled by the
76 Specify a bandwidth limit in bytes per second for mirroring streams.
77 This option is typically used to prevent batch mirroring operations from
78 loading down the machine.
79 The bandwidth may be suffixed with
84 to specify values in kilobytes, megabytes, and gigabytes per second.
85 If no suffix is specified, bytes per second is assumed.
87 When pruning and reblocking you can instruction
89 to start at the object id stored in the specified file.
90 If the file does not exist
92 will start at the beginning.
96 specific period of time and is unable to complete the operation it will
97 write out the current object id so the next run can pick up where it left off.
100 runs to completion it will delete
102 .It Fl f Ar blkdev[:blkdev]*
103 Specify the volumes making up a
107 When maintaining a streaming mirroring this option specifies the
108 minimum delay after a batch ends before the next batch is allowed
110 The default is five seconds.
112 Decrease verboseness.
113 May be specified multiple times.
115 Specify recursion for those commands which support it.
117 When pruning and reblocking you can tell the utility to stop after a
118 certain period of time.
119 This option is used along with the
121 option to prune or reblock a portion of the file system incrementally.
123 Increase verboseness.
124 May be specified multiple times.
126 Force "yes" for any interactive question.
130 will not attempt to break-up large initial bulk transfers into smaller
131 pieces. This can save time but if the link is lost in the middle of the
132 initial bulk transfer you will have to start over from scratch.
133 .It Fl C Ar cachesize[:readahead]
134 Set the memory cache size for any raw I/O. The default is 16m.
135 A suffix of 'k' for kilobytes and 'm' for megabytes is allowed,
136 else the cache size is specified in bytes.
138 The read-behind/read-ahead defaults to 4 hammer blocks.
140 This option is typically only used with diagnostic commands
141 as kernel-supported commands will use the kernel's buffer cache.
144 The commands are as follows:
145 .Bl -tag -width indent
146 .\" ==== synctid ====
147 .It Ar synctid Ar filesystem Op quick
148 Generates a guaranteed, formal 64 bit transaction id representing the
149 current state of the specified
152 The file system will be synced to the media.
156 keyword is specified the file system will be soft-synced, meaning that a
157 crash might still undo the state of the file system as of the transaction
158 id returned but any new modifications will occur after the returned
159 transaction id as expected.
161 .It Ar bstats Op interval
164 B-tree statistics until interrupted.
167 seconds between each display.
168 The default interval is one second.
169 .\" ==== iostats ====
170 .It Ar iostats Op interval
173 I/O statistics until interrupted.
176 seconds between each display.
177 The default interval is one second.
178 .\" ==== history ====
179 .It Ar history Ar path ...
180 Show the modification history for
182 file's inode and data.
183 .\" ==== blockmap ====
185 Dump the blockmap for the filesystem. The HAMMER blockmap is two-layer
186 blockmap representing the maximum possible filesystem size of 1 Exabyte.
187 Needless to say the second layer is only present for blocks which exist.
188 HAMMER's blockmap represents 8-Megabyte blocks. Each block has an append
189 point, a free byte count, and a typed zone id which allows content to be
190 reverse engineered to some degree.
192 In HAMMER allocations essentially appended to a selected big-block using
193 the append offset and deducted from the free byte count. When space is
194 freed the free byte count is adjusted but HAMMER does not track holes in
195 big-blocks for reallocation. A big-block must be completely freed, either
196 through normal filesystem operations or through reblocking, before
199 Data blocks can be shared by deducting the space used from the free byte
200 count for each shared references, though HAMMER does not yet make use of
201 this feature. This means the free byte count can legally go negative.
203 This command needs the
207 .It Ar show Op Ar lo:objid
208 Dump the B-tree. By default this command will validate all B-Tree
209 linkages and CRCs, including data CRCs, and will report the most verbose
210 information it can dig up.
211 Any errors will show up with a 'B' in column 1 along with various
214 If you specify a localization and object id field the dump will
215 search for the key printing nodes as it recurses down, and then
216 will iterate forwards.
220 the command will report less information about the inode contents.
224 the command will not report the content of the inode or other typed
229 the command will not report volume header information, big-block fill
230 ratios, mirror TIDs, or report or check data CRCs. B-Tree CRCs and
231 linkages are still checked.
233 This command needs the
237 .\" Dump the B-tree, record, large-data, and small-data blockmaps, showing
238 .\" physical block assignments and free space percentages.
239 .\" ==== namekey1 ====
240 .It Ar namekey1 Ar filename
243 64 bit directory hash for the specified file name, using
244 the original directory hash algorithm in version 1 of the filesystem.
245 The low 32 bits are used as an iterator for hash collisions and will be
247 .\" ==== namekey2 ====
248 .It Ar namekey2 Ar filename
251 64 bit directory hash for the specified file name, using
252 the new directory hash algorithm in version 2 of the filesystem.
253 The low 32 bits are still used as an iterator but will start out containing
254 part of the hash key.
255 .\" ==== namekey32 ====
256 .It Ar namekey32 Ar filename
257 Generate the top 32 bits of a
259 64 bit directory hash for the specified file name.
262 Shows extended information about all the mounted HAMMER filesystems.
263 At the moment volume identification, big blocks information and space details are shown.
264 .\" ==== cleanup ====
265 .It Ar cleanup Op Ar filesystem ...
266 This is a meta-command which executes snapshot, pruning, and reblocking
267 commands on the specified
272 is specified this command will clean-up all
274 file systems in use, including PFS's.
275 To do this it will scan all
279 mounts, extract PFS id's, and clean-up each PFS found.
281 This command will by default access a
287 creating them if necessary.
288 The format of the configuration file is:
289 .Bd -literal -offset indent
290 snapshots <period> <retention-time> [any]
291 prune <period> <max-runtime>
292 rebalance <period> <max-runtime>
293 reblock <period> <1/3 max-runtime>
294 recopy <period> <1/3 max-runtime>
297 snapshots 1d 60d # 0d 60d for PFS /tmp, /var/tmp, /usr/obj
304 Time is given with a suffix of
310 meaning day, hour, minute and second.
312 If the snapshots directive has a period of 0 and a retention time of 0
313 then snapshot generation is disabled, removal of old snapshots are
314 disabled, and prunes will use
315 .Ar prune-everything .
316 If the snapshots directive has a period of 0 but a non-zero retention time
317 then this command will not create any new snapshots but will remove old
318 snapshots it finds based on the retention time.
320 By default only snapshots in the form: snap-yyyymmdd[-hhmm] are processed.
323 directive is specified as a third argument on the snapshots config line
324 then any softlink of the form *[- or .]yyyymmdd[-hhmm] will be processed.
326 A prune max-runtime of 0 means unlimited.
328 If period hasn't passed since the previous
331 For example a day has passed when midnight is passed (localtime).
339 The default configuration file will create a daily snapshot, do a daily
340 pruning, rebalancing and reblocking run and a monthly recopy run.
341 Reblocking is defragmentation with a level of 95%,
342 and recopy is full defragmentation.
344 By default prune, rebalance and reblock operations are limited to 5 minutes per
345 function, and recopy operations are limited to 10 minutes per function.
346 Reblocking and recopy runs are each broken down into three separate functions
347 (btree, inodes and data)
348 and are thus by default limited to 15 and 30 minutes respectively.
349 Also note that this directive will by default disable snapshots on
356 The defaults may be adjusted by modifying the
359 The pruning and reblocking commands automatically maintain a cyclefile
360 for incremental operation.
361 If you interrupt (^C) the program the cyclefile will be updated, but a sub-command
362 may continue to run in the background for a few seconds until the
364 ioctl detects the interrupt.
367 PFS option can be set to use another location for the snapshots directory.
369 Work on this command is still in progress.
370 Expected additions: An ability to remove snapshots dynamically as the
371 file system becomes full.
373 .It Ar expand Ar filesystem Ar device
374 This command will format
376 and add all of its space to
379 NOTE! All existing data contained on
381 will be destroyed by this operation! If
385 filesystem, formatting will be denied. You can overcome this sanity check
388 to erase the beginning sectors of the device.
389 Also remember that you have to specify
391 together with any other device that make the filesystem, colon-separated to
393 .\" ==== snapshot ====
394 .It Ar snapshot Oo Ar filesystem Oc Ar snapshot-dir
395 Takes a snapshot of the file system either explicitly given by
397 or implicitly derived from the
399 argument and creates a symlink in the directory provided by
401 pointing to the snapshot.
404 is not a directory, it is assumed to be a format string passed to
406 with the current time as parameter.
409 refers to an existing directory, a default format string of "snap-%Y%d%m-%H%M"
410 is assumed and used as name for the newly created symlink.
412 Snapshot is a per PFS operation, so a
414 file system and each PFS in it have to be snapshot separately.
416 Example, assuming that
422 is a file system on its own, the following invocations:
423 .Bd -literal -offset indent
424 hammer snapshot /mysnapshots
426 hammer snapshot /mysnapshots/%Y-%m-%d
428 hammer snapshot /obj /mysnapshots/obj-%Y-%m-%d
431 would create symlinks similar to:
432 .Bd -literal -offset indent
433 /mysnapshots/snap-20080627-1210 -> /@@0x10d2cd05b7270d16
435 /mysnapshots/2008-06-27 -> /@@0x10d2cd05b7270d16
437 /mysnapshots/obj-2008-06-27 -> /obj@@0x10d2cd05b7270d16
440 .It Ar prune Ar softlink-dir
441 Prune the file system based on previously created snapshot softlinks.
442 Pruning is the act of deleting file system history.
446 will delete file system history such that
447 the file system state is retained for the given snapshots,
448 and all history after the latest snapshot,
449 but all other history is deleted.
451 The target directory is expected to contain softlinks pointing to
452 snapshots of the file systems you wish to retain.
453 The directory is scanned non-recursively and the mount points and
454 transaction ids stored in the softlinks are extracted and sorted.
455 The file system is then explicitly pruned according to what is found.
456 Cleaning out portions of the file system is as simple as removing a softlink
461 As a safety measure pruning only occurs if one or more softlinks are found
462 containing the @@ snapshot id extension.
463 Currently the scanned softlink directory must contain softlinks pointing
467 The softlinks may specify absolute or relative paths.
468 Softlinks must use 20-character (@@0x%016llx) transaction ids,
469 as might be returned from
470 .Dq Nm Ar synctid filesystem .
472 Pruning is a per PFS operation, so a
474 file system and each PFS in it have to be pruned separately.
476 Note that pruning a file system may not immediately free-up space,
477 though typically some space will be freed if a large number of records are
479 The file system must be reblocked to completely recover all available space.
481 Example, lets say your snapshot directory contains the following links:
482 .Bd -literal -offset indent
483 lrwxr-xr-x 1 root wheel 29 May 31 17:57 snap1 ->
484 /usr/obj/@@0x10d2cd05b7270d16
486 lrwxr-xr-x 1 root wheel 29 May 31 17:58 snap2 ->
487 /usr/obj/@@0x10d2cd13f3fde98f
489 lrwxr-xr-x 1 root wheel 29 May 31 17:59 snap3 ->
490 /usr/obj/@@0x10d2cd222adee364
493 If you were to run the
495 command on this directory, then the
498 mount will be pruned to retain the above three snapshots.
499 In addition, history for modifications made to the file system older than
500 the oldest snapshot will be destroyed and history for potentially fine-grained
501 modifications made to the file system more recently than the most recent
502 snapshot will be retained.
504 If you then delete the
506 softlink and rerun the
509 history for modifications pertaining to that snapshot would be destroyed.
510 .\" ==== prune-everything ====
511 .It Ar prune-everything Ar filesystem
512 This command will remove all historical records from the file system.
513 This directive is not normally used on a production system.
514 .\" ==== rebalance ====
515 .It Ar rebalance Ar filesystem Op Ar saturation_level
516 This command will rebalance the B-Tree, nodes with small numbers of
517 elements will be combined and element counts will be smoothed out
520 The saturation level is a percentage between 50 and 100. The default
522 .\" ==== reblock ====
523 .It Ar reblock Ar filesystem Op Ar fill_percentage
524 .It Ar reblock-btree Ar filesystem Op Ar fill_percentage
525 .It Ar reblock-inodes Ar filesystem Op Ar fill_percentage
526 .It Ar reblock-dirs Ar filesystem Op Ar fill_percentage
527 .It Ar reblock-data Ar filesystem Op Ar fill_percentage
528 Attempt to defragment and free space for reuse by reblocking a live
531 Big blocks cannot be reused by
533 until they are completely free.
534 This command also has the effect of reordering all elements, effectively
535 defragmenting the file system.
537 The default fill percentage is 100% and will cause the file system to be
538 completely defragmented.
539 All specified element types will be reallocated and rewritten.
540 If you wish to quickly free up space instead try specifying
541 a smaller fill percentage, such as 90% or 80% (the
543 suffix is not needed).
545 Since this command may rewrite the entire contents of the disk it is
546 best to do it incrementally from a
552 options to limit the run time.
553 The file system would thus be defragmented over long period of time.
555 It is recommended that separate invocations be used for each data type.
556 B-tree nodes, inodes, and directories are typically the most important
557 elements needing defragmentation.
558 Data can be defragmented over a longer period of time.
560 Reblocking is a per PFS operation, so a
562 file system and each PFS in it have to be reblocked separately.
563 .\" ==== pfs-status ====
564 .It Ar pfs-status Ar dirpath ...
565 Retrieve the mirroring configuration parameters for the specified
567 file systems or pseudo-filesystems (PFS's).
568 .\" ==== pfs-master ====
569 .It Ar pfs-master Ar dirpath Op options
570 Create a pseudo-filesystem (PFS) inside a
573 Up to 65535 such file systems can be created.
574 Each PFS uses an independent inode numbering space making it suitable
575 for use as a replication source or target.
579 directive creates a PFS that you can read, write, and use as a mirroring
582 It is recommended to use a
584 mount to access a PFS, for more information see
586 .\" ==== pfs-slave ====
587 .It Ar pfs-slave Ar dirpath Op options
588 Create a pseudo-filesystem (PFS) inside a
591 Up to 65535 such file systems can be created.
592 Each PFS uses an independent inode numbering space making it suitable
593 for use as a replication source or target.
597 directive creates a PFS that you can use as a mirroring target.
598 You will not be able to access a slave PFS until you have completed the
599 first mirroring operation with it as the target (its root directory will
600 not exist until then).
602 Access to the pfs-slave via the special softlink,
608 dynamically modify the snapshot transaction id by returning a dynamic result
613 A PFS can only be truly destroyed with the
616 Removing the softlink will not destroy the underlying PFS.
618 It is recommended to use a
620 mount to access a PFS, for more information see
622 .\" ==== pfs-update ====
623 .It Ar pfs-update Ar dirpath Op options
624 Update the configuration parameters for an existing
627 or pseudo-filesystem.
628 Options that may be specified:
629 .Bl -tag -width indent
630 .It sync-beg-tid=0x16llx
631 This is the automatic snapshot access starting transaction id for
633 This parameter is normally updated automatically by the
637 It is important to note that accessing a mirroring slave
638 with a transaction id greater than the last fully synchronized transaction
639 id can result in an unreliable snapshot since you will be accessing
640 data that is still undergoing synchronization.
642 Manually modifying this field is dangerous and can result in a broken
644 .It sync-end-tid=0x16llx
645 This is the current synchronization point for mirroring slaves.
646 This parameter is normally updated automatically by the
650 Manually modifying this field is dangerous and can result in a broken mirror.
651 .It shared-uuid=<uuid>
652 Set the shared UUID for this file system.
653 All mirrors must have the same shared UUID.
654 For safety purposes the
656 directives will refuse to operate on a target with a different shared UUID.
658 Changing the shared UUID on an existing, non-empty mirroring target,
659 including an empty but not completely pruned target,
660 can lead to corruption of the mirroring target.
661 .It unique-uuid=<uuid>
662 Set the unique UUID for this file system.
663 This UUID should not be used anywhere else,
664 even on exact copies of the file system.
666 Set a descriptive label for this file system.
667 .It snapshots=<string>
668 Specify the snapshots directory which
671 will use to manage this PFS.
672 The snapshots directory does not need to be configured for
673 PFS masters and will default to
674 .Pa <pfs>/snapshots .
676 PFS slaves are mirroring slaves so you cannot configure a snapshots
677 directory on the slave itself to be managed by the slave's machine.
678 In fact, the slave will likely have a
680 sub-directory mirrored
681 from the master, but that directory contains the configuration the master
682 is using for its copy of the file system, not the configuration that we
683 want to use for our slave.
685 It is recommended that
686 .Pa <fs>/var/slaves/<name>
687 be configured for a PFS slave, where
693 is an appropriate label.
694 You can control snapshot retention on your slave independent of the master.
696 Zero out the snapshots directory path for this PFS.
698 .It prune-min=Nd/hh[:mm[:ss]]
699 .It prune-min=hh[:mm[:ss]]
700 Set the minimum fine-grained data retention period.
702 always retains fine-grained history up to the most recent snapshot.
703 You can extend the retention period further by specifying a non-zero
704 pruning minimum. Any snapshot softlinks within the retention period
705 are ignored for the purposes of pruning (the fine grained history
708 Because the transaction id in the snapshot softlink cannot be used
709 to calculate a timestamp,
711 uses the earlier of the st_ctime or st_mtime field of the softlink to
712 determine which snapshots fall within the retention period.
713 Users must be sure to retain one of these two fields when manipulating
716 .\" ==== pfs-upgrade ====
717 .It Ar pfs-upgrade Ar dirpath
718 Upgrade a PFS from slave to master operation.
719 The PFS will be rolled back to the current end synchronization tid
720 (removing any partial synchronizations), and will then become writable.
724 currently supports only single masters and using
725 this command can easily result in file system corruption
726 if you don't know what you are doing.
728 This directive will refuse to run if any programs have open descriptors
729 in the PFS, including programs chdir'd into the PFS.
730 .\" ==== pfs-downgrade ====
731 .It Ar pfs-downgrade Ar dirpath
732 Downgrade a master PFS from master to slave operation
733 The PFS becomes read-only and access will be locked to its
736 This directive will refuse to run if any programs have open descriptors
737 in the PFS, including programs chdir'd into the PFS.
738 .\" ==== pfs-destroy ====
739 .It Ar pfs-destroy Ar dirpath
740 This permanently destroys a PFS.
742 This directive will refuse to run if any programs have open descriptors
743 in the PFS, including programs chdir'd into the PFS.
744 .\" ==== mirror-read ====
745 .It Ar mirror-read Ar filesystem Op Ar <begin-tid>
746 Generate a mirroring stream to stdout.
747 The stream ends when the transaction id space has been exhausted.
748 .\" ==== mirror-read-stream ====
749 .It Ar mirror-read-stream Ar filesystem Op Ar <begin-tid>
750 Generate a mirroring stream to stdout.
751 Upon completion the stream is paused until new data is synced to the
752 master, then resumed.
753 Operation continues until the pipe is broken.
754 .\" ==== mirror-write ====
755 .It Ar mirror-write Ar filesystem
756 Take a mirroring stream on stdin.
758 This command will fail if the
760 configuration field for the two file systems do not match.
762 If the target PFS does not exist this command will ask you whether
763 you want to create a compatible PFS slave for the target or not.
764 .\" ==== mirror-dump ====
770 to dump an ASCII representation of the mirroring stream.
771 .\" ==== mirror-copy ====
772 .It Ar mirror-copy Ar [[user@]host:]filesystem Ar [[user@]host:]filesystem
773 This is a shortcut which pipes a
778 If a remote host specification is made the program forks a
784 on the appropriate host.
785 The source may be a master or slave PFS, and the target must be a slave PFS.
787 This command also established full duplex communication and turns on
788 the two-way protocol feature which automatically negotiates transaction id
789 ranges without having to use a cyclefile.
790 If the operation completes successfully the target PFS's
793 Note that you must re-chdir into the target PFS to see the updated information.
794 If you do not you will still be in the previous snapshot.
796 If the target PFS does not exist this command will ask you whether
797 you want to create a compatible PFS slave for the target or not.
798 .\" ==== mirror-stream ====
799 .It Ar mirror-stream Ar [[user@]host:]filesystem Ar [[user@]host:]filesystem
800 This command works similarly to
802 but does not exit after the initial mirroring completes.
803 The mirroring operation will resume as changes continue to be made to the
805 The command is commonly used with
809 options to keep the mirroring target in sync with the source on a continuing
812 If the pipe is broken the command will automatically retry after sleeping
813 for a short while. The time slept will be 15 seconds plus the time given
818 This command also detects the initial-mirroring case and spends some
819 time scanning the B-Tree to find good break points, allowing the initial
820 bulk mirroring operation to be broken down into about 20 separate pieces.
821 This means that the user can kill and restart the operation and it will
822 not have to start from scratch once it has gotten past the first chunk.
825 option may be used to disable this feature and perform an initial bulk
827 .\" ==== version ====
828 .It Ar version Ar filesystem
829 This command returns the
831 filesystem version for the specified
832 filesystem as well as the range of versions supported in the kernel.
835 option may be used to remove the summary at the end.
836 .\" ==== version-upgrade ====
837 .It Ar version-upgrade Ar filesystem Ar version Op Ar force
838 This command upgrades the
840 filesystem to the specified version.
841 Once upgraded a filesystem may not be downgraded.
842 If you wish to upgrade a filesystem to a version greater or equal to the
843 work-in-progress version number you must specify the
846 Use of WIP versions should be relegated to testing and may require wiping
847 the filesystem as development progresses, even though the WIP version might
850 NOTE! This command operates on the entire
852 filesystem and is not a per-PFS operation.
853 All PFS's will be affected.
854 .Bl -tag -width indent
857 default version, first
861 Work-in-progress version.
862 This version is developing a new directory hash key.
866 .Sh PSEUDO FILESYSTEM (PFS) NOTES
867 The root of a PFS is not hooked into the primary
869 file system as a directory.
872 creates a special softlink called "@@PFS%05d" (exactly 10 characters long)
877 then modifies the contents of the softlink as read by
879 and thus what you see with an
881 command or if you were to
884 If the PFS is a master the link reflects the current state of the PFS.
885 If the PFS is a slave the link reflects the last completed snapshot, and the
886 contents of the link will change when the next snapshot is completed, and
889 PFS support is currently very new and experimental.
892 utility employs numerous safeties to reduce user foot-shooting.
895 directive requires that the target be configured as a slave and that the
897 field of the mirroring source and target match.
899 .Bl -tag -width ".It Pa <fs>/var/slaves/<name>" -compact
901 default per PFS snapshots directory
902 .It Pa <snapshots>/config
906 .It Pa <fs>/var/slaves/<name>
907 recommended slave PFS snapshots directory
914 .Xr periodic.conf 5 ,
921 utility first appeared in
924 .An Matthew Dillon Aq dillon@backplane.com
projects / dragonfly.git / blob