1 .TH snap.lvm 8 "6 November 2011" "distorted.org.uk backup"
3 snap.lvm \- snapshot handler for LVM logical volumes
10 This is a snapshot handler for LVM volumes: see
12 for more information about how snapshot handlers fit into the overall
13 system. It creates or removes a snapshot of the logical volume named
18 The following options keys are recognized, either with a
20 suffix or without. Other keys are reported as errors, unless the key
30 (the default) to create a snapshot, or
35 The snapshot volume will be named
36 .IB lv-name . tag \fR.
39 It is recommended that scripts always provide a tag identifying their
43 The size to allocate for the snapshot's backing store. This may be an
44 absolute size followed by an optional unit suffix
51 for kilobytes, megabytes (the default), terabytes, petabytes, or
52 exabytes, respectively; or a relative size of the form
63 of the total space in the volume group, the free space remaining in the
64 volume group, or the size of the origin volume, respectively. (The
66 suffix may be abbreviated to just the first letter; the suffixes are not
67 case-sensitive in either case.)
69 The LVM tools are rather buggy, and exhibit nasty races with
73 tool is particularly awful.
78 to work around these bugs.
80 If you make a snapshot of a logical volume while a filesystem is
81 directly mounted from the logical volume on the same machine, and the
82 filesystem kernel driver implements the
86 superblock operations, then the kernel will arrange for the snapshot to
87 contain a consistent and clean snapshot of the filesystem \(en in
88 particular, it shouldn't need the ministrations of
90 If the filesystem is mounted by a different machine, e.g., a guest
91 running on the same host, or via a network block-device access protocol,
92 you will need to negotiate with the remote machine in order to obtain a
94 .BR snap.rfreezefs (8)
95 for a snapshot handler which copes with this, and
97 for the actual machinery.
104 Mark Wooding, <mdw@distorted.org.uk>