Provided by: samba-vfs-modules_4.3.11+dfsg-0ubuntu0.16.04.34_amd64 
NAME
vfs_shadow_copy2 - Expose snapshots to Windows clients as shadow copies.
SYNOPSIS
vfs objects = shadow_copy2
DESCRIPTION
This VFS module is part of the samba(7) suite.
The vfs_shadow_copy2 VFS module offers a functionality similar to Microsoft Shadow Copy services. When
set up properly, this module allows Microsoft Shadow Copy clients to browse through file system snapshots
as "shadow copies" on Samba shares.
This is a second implementation of a shadow copy module which has the following additional features
(compared to the original shadow_copy(8) module):
1. There is no need any more to populate your share's root directory with symlinks to the snapshots if
the file system stores the snapshots elsewhere. Instead, you can flexibly configure the module where
to look for the file system snapshots. This can be very important when you have thousands of shares,
or use [homes].
2. Snapshot directories need not be in one fixed central place but can be located anywhere in the
directory tree. This mode helps to support file systems that offer snapshotting of particular
subtrees, for example the GPFS independent file sets.
3. Vanity naming for snapshots: snapshots can be named in any format compatible with str[fp]time
conversions.
4. Timestamps can be represented in localtime rather than UTC.
5. The inode number of the files can optionally be altered to be different from the original. This fixes
the 'restore' button in the Windows GUI to work without a sharing violation when serving from file
systems, like GPFS, that return the same device and inode number for the snapshot file and the
original.
6. Shadow copy results are by default sorted before being sent to the client. This is beneficial for
filesystems that don't read directories alphabetically (the default unix). Sort ordering can be
configured and sorting can be turned off completely if the file system sorts its directory listing.
This module is stackable.
CONFIGURATION
vfs_shadow_copy2 relies on a filesystem snapshot implementation. Many common filesystems have native
support for this.
Filesystem snapshots must be available under specially named directories in order to be recognized by
vfs_shadow_copy2. These snapshot directory is typically a direct subdirectory of the share root's
mountpoint but there are other modes that can be configured with the parameters described in detail
below.
The snapshot at a given point in time is expected in a subdirectory of the snapshot directory where the
snapshot's directory is expected to be a formatted version of the snapshot time. The default format which
can be changed with the shadow:format option is @GMT-YYYY.MM.DD-hh.mm.ss, where:
• YYYY is the 4 digit year
• MM is the 2 digit month
• DD is the 2 digit day
• hh is the 2 digit hour
• mm is the 2 digit minute
• ss is the 2 digit second.
The vfs_shadow_copy2 snapshot naming convention can be produced with the following date(1) command:
TZ=GMT date +@GMT-%Y.%m.%d-%H.%M.%S
OPTIONS
shadow:mountpoint = MOUNTPOINT
With this parameter, one can specify the mount point of the filesystem that contains the share path.
Usually this mount point is automatically detected. But for some constellations, in particular tests,
it can be convenient to be able to specify it.
Example: shadow:mountpoint = /path/to/filesystem
Default: shadow:mountpoint = NOT SPECIFIED
shadow:snapdir = SNAPDIR
Path to the directory where the file system of the share keeps its snapshots. If an absolute path is
specified, it is used as-is. If a relative path is specified, then it is taken relative to the mount
point of the filesystem of the share root. (See shadow:mountpoint.)
Note that shadow:snapdirseverywhere depends on this parameter and needs a relative path. Setting an
absolute path disables shadow:snapdirseverywhere.
Note that the shadow:crossmountpoints option also requires a relative snapdir. Setting an absolute
path disables shadow:crossmountpoints.
Example: shadow:snapdir = /some/absolute/path
Default: shadow:snapdir = .snapshots
shadow:basedir = BASEDIR
The basedir option allows to specify a directory between the share's mount point and the share root,
relative to which the file system's snapshots are taken.
For example, if
• basedir = mountpoint/rel_basedir
• share_root = basedir/rel_share_root
• snapshot_path = mountpoint/snapdir
or snapshot_path = snapdir if snapdir is absolute
then the snapshot of a file = mountpoint/rel_basedir/rel_share_root/rel_file at a time TIME will be found
under snapshot_path/FS_GMT_TOKEN(TIME)/rel_share_root/rel_file, where FS_GMT_TOKEN(TIME) is the timestamp
string belonging to TIME in the format required by the file system. (See shadow:format.)
The default for the basedir is the mount point of the file system of the share root (see
shadow:mountpoint).
Note that the shadow:snapdirseverywhere and shadow:crossmountpoints options are incompatible with
shadow:basedir and disable the basedir setting.
shadow:sort = asc/desc
By default, this module sorts the shadow copy data alphabetically before sending it to the client.
With this parameter, one can specify the sort order. Possible known values are desc (descending, the
default) and asc (ascending). If the file system lists directories alphabetically sorted, one can
turn off sorting in this module by specifying any other value.
Example: shadow:sort = asc
Example: shadow:sort = none
Default: shadow:sort = desc
shadow:localtime = yes/no
This is an optional parameter that indicates whether the snapshot names are in UTC/GMT or in local
time. If it is disabled then UTC/GMT is expected.
shadow:localtime = no
shadow:format = format specification for snapshot names
This is an optional parameter that specifies the format specification for the naming of snapshots in
the file system. The format must be compatible with the conversion specifications recognized by
str[fp]time.
Default: shadow:format = "@GMT-%Y.%m.%d-%H.%M.%S"
shadow:sscanf = yes/no
This paramter can be used to specify that the time in format string is given as an unsigned long
integer (%lu) rather than a time strptime() can parse. The result must be a unix time_t time.
Default: shadow:sscanf = no
shadow:fixinodes = yes/no
If you enable shadow:fixinodes then this module will modify the apparent inode number of files in the
snapshot directories using a hash of the files path. This is needed for snapshot systems where the
snapshots have the same device:inode number as the original files (such as happens with GPFS
snapshots). If you don't set this option then the 'restore' button in the shadow copy UI will fail
with a sharing violation.
Default: shadow:fixinodes = no
shadow:snapdirseverywhere = yes/no
If you enable shadow:snapdirseverywhere then this module will look out for snapshot directories in
the current working directory and all parent directories, stopping at the mount point by default. But
see shadow:crossmountpoints how to change that behaviour.
An example where this is needed are independent filesets in IBM's GPFS, but other filesystems might
support snapshotting only particular subtrees of the filesystem as well.
Note that shadow:snapdirseverywhere depends on shadow:snapdir and needs it to be a relative path.
Setting an absolute snapdir path disables shadow:snapdirseverywhere.
Note that this option is incompatible with the shadow:basedir option and removes the shadow:basedir
setting by itself.
Example: shadow:snapdirseverywhere = yes
Default: shadow:snapdirseverywhere = no
shadow:crossmountpoints = yes/no
This option is effective in the case of shadow:snapdirseverywhere = yes. Setting this option makes
the module not stop at the first mount point encountered when looking for snapdirs, but lets it
search potentially all through the path instead.
An example where this is needed are independent filesets in IBM's GPFS, but other filesystems might
support snapshotting only particular subtrees of the filesystem as well.
Note that shadow:snapdirseverywhere depends on shadow:snapdir and needs it to be a relative path.
Setting an absolute snapdir path disables shadow:snapdirseverywhere.
Note that this option is incompatible with the shadow:basedir option and removes the shadow:basedir
setting by itself.
Example: shadow:crossmountpoints = yes
Default: shadow:crossmountpoints = no
EXAMPLES
Add shadow copy support to user home directories:
[homes]
vfs objects = shadow_copy2
shadow:snapdir = /data/snapshots
shadow:basedir = /data/home
shadow:sort = desc
CAVEATS
This is not a backup, archival, or version control solution.
With Samba or Windows servers, vfs_shadow_copy2 is designed to be an end-user tool only. It does not
replace or enhance your backup and archival solutions and should in no way be considered as such.
Additionally, if you need version control, implement a version control system.
VERSION
This man page is correct for version 4.0 of the Samba suite.
AUTHOR
The original Samba software and related utilities were created by Andrew Tridgell. Samba is now developed
by the Samba Team as an Open Source project similar to the way the Linux kernel is developed.
Samba 4.3 04/14/2021 VFS_SHADOW_COPY2(8)