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33 .\" $DragonFly: src/sbin/hammer/hammer.8,v 1.16 2008/05/13 20:49:34 dillon 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
84 Generate a timestamp suitable for use in the @@ filename extension,
85 representing right now.
87 Generate a full 64 bit timestamp.
92 directives do not generate a guaranteed transaction id.
95 command to generate a guaranteed transaction id.
97 Generate a timestamp suitable for use in the @@ filename extension.
98 This command does not sync() or sleep and care should be taken if
99 generating timestamps for data which may not yet be synced to disk.
100 A time specification of
101 .Pf yyyymmdd Oo :hhmmss Oc Ns Op .fractional
102 specifies an exact as-of timestamp in local (not UTC) time.
103 Set the TZ environment variable prior to running
105 if you wish to specify the time by some other means.
109 command but generates a 64 bit timestamp.
110 .It Ar synctid Ar filesystem Op quick
111 Generates a guaranteed, formal 64 bit transaction id representing the
112 current state of the specified HAMMER filesystem. The filesystem will
113 be synced to the media.
117 keyword is specified the filesystem will be soft-synced, meaning that a
118 crash might still undo the state of the filesystem as of the transaction
119 id returned but any new modifications will occur after the returned
120 transaction id as expected.
122 Output a date equivalent given a transaction id or time stamp.
123 .It Ar history Ar path
124 Show the modification history for a HAMMER file's inode and data.
125 .It Ar show Op vol_no[:clu_no]
126 Dump the B-Tree starting at the specified volume and cluster, or
127 at the root volume if not specified.
128 The B-Tree is dumped recursively if the
132 Dump the btree, record, large-data, and small-data blockmaps, showing
133 physical block assignments and free space percentages.
134 .It Ar namekey Ar filename
135 Generate a HAMMER 64 bit directory hash for the specified file name.
136 The low 32 bits are used as an iterator for hash collisions and will be
138 .It Ar namekey32 Ar filename
139 Generate the top 32 bits of a HAMMER 64 bit directory hash for the specified
141 .It Ar prune Ar filesystem Ar from Ar #{smhdMy} Ar to Ar #{smhdMy} Ar every Ar #{smhdMy}
142 .It Ar prune Ar filesystem Ar from Ar #{smhdMy} Ar everything
143 .It Ar prune Ar filesystem Ar everything
144 .It Ar prune Ar filesystem Op Ar using Ar filename
145 Prune the filesystem, removing deleted records to free up physical disk
146 space. Specify a time range between the nearest modulo 0 boundary
147 and prune the tree to the specified granularity within that range.
149 The filesystem specification should be the root of any mounted HAMMER
150 filesystem. This command uses a filesystem ioctl to issue the pruning
151 operation. If you specify just the filesystem with no other parameters
152 all prune directives matching that filesystem in the /etc/hammer.conf file
153 will be used. If you specify a
155 file then those directives contained in the file matching
157 will be used. Multiple directives may be specified when extracting from
158 a file. The directives must be in the same format: "prune ....", in
159 ascending time order (per filesystem). Matching prune elements must not
160 have overlapping time specifications.
162 Both the "from" and the "to" value must be an integral multiple
163 of the "every" value, and the "to" value must be an integral multiple
164 of the "from" value. When you have multiple pruning rules you must
165 take care to ensure that the range being pruned does not overlap ranges
166 pruned later on, when the retained data is older. If they do the retained
167 data can wind up being destroyed. For example, if you prune your data
168 on a 30 minute granularity for the last 24 hours any later pruning must
169 use a granularity that is a multiple of 30 minutes. If you prune your
170 data on a 30 minute boundary, then a 1 day boundary in a later pruning (on
171 older data), then a pruning beyond that would have to be a multiple of
174 The "prune <filesystem> from ... everything" command will remove all
175 historical records older then the specified date. It is a way of saying
176 that you do not want to retain any deleted information past a certain point.
178 The "prune <filesystem> everything" command will remove all historical records
179 from the filesystem. The long keyword is designed to prevent accidental use.
180 This option is not recommended.
182 Example: "hammer prune /mnt from 1h to 1d every 30m"
184 Note that pruning a filesystem does not necessarily immediately free space,
185 though typically some space will be freed if a large number of records are
186 pruned out. The filesystem must be reblocked to completely recover all
188 .It Ar reblock Ar filesystem Op Ar fill_percentage
189 .It Ar reblock-btree Ar filesystem Op Ar fill_percentage
190 .It Ar reblock-data Ar filesystem Op Ar fill_percentage
191 .It Ar reblock-recs Ar filesystem Op Ar fill_percentage
192 Attempt to free space for reuse by reblocking a live HAMMER filesystem.
193 Big blocks cannot be reused until they are completely free. Scan the
194 filesystem and move B-Tree nodes, records, and data from not-quite-full
195 big blocks to new big blocks in an attempt to free up the not-quite-full
198 If unspecified a fill percentage of 90% is used. B-Tree nodes, data,
199 and records can be reblocked together or by separate invocations.
201 A HAMMER filesystem can be defragmented by specifying a fill percentage
202 of 100%. Since this can potentially rewrite the entire contents of the
203 disk it is best to do it incrementally from a cron job with a timeout.
204 The filesystem would thus be defragmented over long period of time.
208 Exit status is 0 on success and 1 on error.
214 utility first appeared in
217 .An Matthew Dillon Aq dillon@backplane.com