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32 .\" $DragonFly: src/share/man/man5/hammer.5,v 1.4 2008/07/17 09:41:19 swildner Exp $
39 .Nd HAMMER file system
41 To compile this driver into the kernel,
42 place the following line in your
43 kernel configuration file:
44 .Bd -ragged -offset indent
48 Alternatively, to load the driver as a
49 module at boot time, place the following line in
51 .Bd -literal -offset indent
57 .Bd -literal -offset indent
58 /dev/ad0s1d[:/dev/ad1s1d:...] /mnt hammer rw 2 0
63 file system provides facilities to store file system data onto a disk device
64 and is intended to replace UFS as the default file system for
66 Among its features are fine grained history retention, file systems spanning
67 multiple volumes, mirroring capability, and pseudo file systems.
69 All functions related to managing
71 file systems are provided by the
81 file system uses 64 bit, hexadecimal transaction IDs to refer to historical
82 file or directory data.
86 .Li 0x00000001061a8ba6 .
88 History metadata on the media is updated with every sync operation.
89 Prior versions of files or directories are accessible by appending
91 and a transaction ID to the name.
94 file system will free all unused historical records.
96 A snapshot can be taken by creating a symbolic link to a specific
97 version of a file or directory.
98 Snapshots created this way will be retained across subsequent prune
100 Removing the symbolic link enables the file system to reclaim the space
103 .\".Ss Pseudo File Systems
105 .Ss Preparing the file system
106 To create and mount a
115 file systems must have a unique name on a per-machine basis.
117 newfs_hammer -L Home /dev/ad0s1d
118 mount_hammer /dev/ad0s1d /home
121 Similarly, multi volume file systems can be created and mounted by
122 specifying additional arguments.
124 newfs_hammer -L MultiHome /dev/ad0s1d /dev/ad1s1d
125 mount_hammer /dev/ad0s1d /dev/ad1s1d /home
128 Once created and mounted,
130 file systems need to be reblocked periodically in order not to fill up
131 over time, either manually or with a
134 It is recommended that the
140 options be used for this job (for example, every night at 2:15 up to 5
143 15 2 * * * hammer -c /var/run/Home -t 300 reblock /home >/dev/null 2>&1
153 .%T "The HAMMER Filesystem"
158 file system first appeared in
164 file system was designed and implemented by
165 .An Matthew Dillon Aq dillon@backplane.com .
166 This manual page was written by