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33 .\" $DragonFly: src/sbin/hammer/hammer.8,v 1.29 2008/06/28 14:51:50 swildner Exp $
39 .Nd HAMMER file system utility
44 .Op Fl f Ar blkdev[:blkdev]*
52 utility provides miscellaneous functions related to managing a HAMMER
55 The options are as follows:
56 .Bl -tag -width indent
60 Specify recursion for those commands which support it.
62 When pruning and reblocking you can instruction HAMMER to start at the
63 object id stored in the specified file. If the file does not exist
64 HAMMER will start at the beginning. If HAMMER is told to run for a
65 specific period of time and is unable to complete the operation it will
66 write out the current obj_id so the next run can pick up where it left
67 off. If HAMMER runs to completion it will delete the cyclefile.
68 .It Fl f Ar blkdev[:blkdev]*
69 Specify the volumes making up a HAMMER filesystem.
71 When pruning a filesystem you can instruct HAMMER to create softlinks
72 to available snapshots.
74 When pruning and reblocking you can tell the utility to stop after a
75 certain period of time. This option is used along with the cycle file
76 option to prune or reblock a portion of the filesystem incrementally.
78 Increase verboseness. May be specified multiple times.
81 The commands are as follows:
82 .Bl -tag -width indent
83 .It Ar synctid Ar filesystem Op quick
84 Generates a guaranteed, formal 64 bit transaction id representing the
85 current state of the specified HAMMER filesystem. The filesystem will
86 be synced to the media.
90 keyword is specified the filesystem will be soft-synced, meaning that a
91 crash might still undo the state of the filesystem as of the transaction
92 id returned but any new modifications will occur after the returned
93 transaction id as expected.
94 .It Ar bstats Op interval
95 Output HAMMER B-Tree statistics until interrupted. The default interval
97 .It Ar iostats Op interval
98 Output HAMMER I/O statistics until interrupted. The default interval
100 .It Ar history Ar path
101 Show the modification history for a HAMMER file's inode and data.
102 .It Ar show Op vol_no[:clu_no]
103 Dump the B-Tree starting at the specified volume and cluster, or
104 at the root volume if not specified.
105 The B-Tree is dumped recursively if the
109 Dump the btree, record, large-data, and small-data blockmaps, showing
110 physical block assignments and free space percentages.
111 .It Ar namekey Ar filename
112 Generate a HAMMER 64 bit directory hash for the specified file name.
113 The low 32 bits are used as an iterator for hash collisions and will be
115 .It Ar namekey32 Ar filename
116 Generate the top 32 bits of a HAMMER 64 bit directory hash for the specified
118 .It Ar prune Ar softlink-dir
119 Prune the filesystem based on previously created snapshot softlinks.
120 The target directory is expected to contain softlinks pointing to
121 snapshots of the filesystems you wish to retain. The directory is scanned
122 non-recursively and the mount points and transaction ids stored in the
123 softlinks are extracted and sorted.
124 The filesystem is then explicitly pruned according to what is found.
125 Cleaning out portions of the filesystem is as simple as removing a softlink
130 As a safety measure pruning only occurs if one or more softlinks are found
131 containing the @@ snapshot id extension.
133 Currently the scanned softlink directory must contain softlinks pointing
134 to a single HAMMER mount. The softlinks may specify absolute or relative
135 paths. Softlinks must use 20-character (@@0x%016llx) transaction ids,
136 as might be returned from 'hammer synctid <filesystem>'.
138 Example, lets say your snapshot directory contains the following links:
140 lrwxr-xr-x 1 root wheel 29 May 31 17:57 snap1 ->
141 /usr/obj/@@0x10d2cd05b7270d16
143 lrwxr-xr-x 1 root wheel 29 May 31 17:58 snap2 ->
144 /usr/obj/@@0x10d2cd13f3fde98f
146 lrwxr-xr-x 1 root wheel 29 May 31 17:59 snap3 ->
147 /usr/obj/@@0x10d2cd222adee364
150 If you were to run the prune command on this directory, then the HAMMER
152 mount will be pruned to retain the above three snapshots.
153 In addition, modifications made to the filesystem older than the oldest
154 snapshot will be destroyed and potentially fine-grained modifications made
155 to the filesystem more recently than the most recent snapshot will be
158 If you then delete the snap2 softlink and rerun the prune command,
159 modifications pertaining to that snapshot would be destroyed.
160 .It Ar prune-everything Ar filesystem
161 This command will remove all historical records from the filesystem.
162 This directive is not normally used on a production system.
164 Note that pruning a filesystem may not immediately free-up space,
165 though typically some space will be freed if a large number of records are
166 pruned out. The filesystem must be reblocked to completely recover all
168 .It Ar snapshot Ar snapshot-dir
169 .It Ar snapshot Ar filesystem snapshot-dir
170 Takes a snapshot of the filesystem either explicitly given by
172 or implicitly derived from the
174 argument and creates a symlink in the directory provided by
176 pointing to the snapshot.
179 is no directory, it is assumed to be a format string
182 with the current time as parameter.
185 refers to an existing directory, a default format string of "snap-%Y%d%m-%H%M"
186 is assumed and used as name for the newly created symlink.
193 is a filesystem on its own, the following invocations:
195 hammer snapshot /mysnapshots
197 hammer snapshot /mysnapshots/%Y-%m-%d
199 hammer snapshot /obj /mysnapshots/obj-%Y-%m-%d
202 would create symlinks similar to:
204 /mysnapshots/snap-20080627-1210 -> /@@0x10d2cd05b7270d16
206 /mysnapshots/2008-06-27 -> /@@0x10d2cd05b7270d16
208 /mysnapshots/obj-2008-06-27 -> /obj@@0x10d2cd05b7270d16
210 .It Ar reblock Ar filesystem Op Ar fill_percentage
211 .It Ar reblock-btree Ar filesystem Op Ar fill_percentage
212 .It Ar reblock-inodes Ar filesystem Op Ar fill_percentage
213 .It Ar reblock-dirs Ar filesystem Op Ar fill_percentage
214 .It Ar reblock-data Ar filesystem Op Ar fill_percentage
215 Attempt to defragment and free space for reuse by reblocking a live
217 Big blocks cannot be reused by HAMMER until they are completely free.
218 This command also has the effect of reordering all elements, effectively
219 defragmenting the filesystem.
221 The default fill percentage is 100% and will cause the filesystem to be
222 completely defragmented. All specified element types will be reallocated
223 and rewritten. If you wish to quickly free up space instead try specifying
224 a smaller fill percentage, such as 90% or 80% (the '%' suffix is not needed).
226 Since this command may rewrite the entire contents of the disk it is
227 best to do it incrementally from a cron job along with the
231 options to limit the run time.
232 The filesystem would thus be defragmented over long period of time.
234 It is recommended that separate invocations be used for each data type.
235 Btree nodes, inodes, and directories are typically the most important
236 elements needing defragmentation. Data can be defragmented over a longer
238 .It Ar pseudofs Ar dirpath
239 Create a pseudo-filesystem inside a HAMMER filesystem. Up to 65535 such
240 filesystems can be created. Each one uses an independant inode numbering
241 space making it suitable for use as a replication source or target.
251 utility first appeared in
254 .An Matthew Dillon Aq dillon@backplane.com