1 .TH snap.ro 8 "12 November 2011" "distorted.org.uk backup"
3 snap.ro \- fake snapshot handler which remounts filesystems read-only
10 This is a fake snapshot handler. Rather than produce a snapshot device
11 containing a consistent view of the origin's contents, it simply
12 remounts the contained filesystem read-only. Obviously, this isn't
13 satisfactory for operations which might alter the block device, but it's
14 fine for stuff like backups.
16 The following options keys are recognized, either with a
18 suffix or without. Other keys are reported as errors, unless the key
28 (the default) to create a `snapshot' \(en i.e., remount read-only \(en or
30 to remove it \(en i.e., remount read/write.
33 On snapshot creation, record the
35 in the filesystem before remounting readonly; on snapshot removal,
36 verify that the tag recorded matches
38 This prevents a different script from making the filesystem read/write
39 prematurely. The default tag is
42 The filesystem is mounted on
44 If you omit this option,
48 for a mount point for the given
50 If exactly one such mount point is found then it will be used;
51 otherwise, an error is reported.
53 This assumes that the filesystem is mounted locally. If the block device
54 is exported (e.g., to a virtual guest, or using a network block device)
55 then this won't work and you'll need to do something more complicated.
57 Linux allows the same device to be mounted in several different places
58 using bind mounts. Each of these occurrences needs to be made read-only
59 if the device contents are to be made consistent;
61 is too stupid to handle this properly: instead, if
63 is omitted, it checks that the device is mentioned exactly once in
69 Mark Wooding, <mdw@distorted.org.uk>