VFS_SHADOW_COPY2(8) System Administration tools VFS_SHADOW_COPY2(8)NAMEvfs_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.
CONFIGURATIONvfs_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 one 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:snapsharepath = SNAPSHAREPATH
With this parameter, one can specify the path of the share's root
directory in snapshots, relative to the snapshot's root directory.
It is an alternative method to shadow:basedir, allowing greater
control.
For example, if within each snapshot the files of the share have a
path/to/share/ prefix, then shadow:snapsharepath can be set to
path/to/share.
With this parameter, it is no longer assumed that a snapshot
represents an image of the original file system or a portion of it.
For example, a system could perform backups of only files contained
in shares, and then expose the backup files in a logical structure:
· share1/
· share2/
· .../
Note that the shadow:snapdirseverywhere and the shadow:basedir
options are incompatible with shadow:snapsharepath and disable
shadow:snapsharepath setting.
Example: shadow:snapsharepath = path/to/share
Default: shadow:snapsharepath = NOT SPECIFIED
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 parameter 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:crossmountpoints depends on shadow:snapdir and
needs it to be a relative path. Setting an absolute snapdir path
disables shadow:crossmountpoints.
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
shadow:snapprefix
With growing number of snapshots file-systems need some mechanism
to differentiate one set of snapshots from other, e.g. monthly,
weekly, manual, special events, etc. Therefore these file-systems
provide different ways to tag snapshots, e.g. provide a
configurable way to name snapshots, which is not just based on
time. With only shadow:format it is very difficult to filter these
snapshots. With this optional parameter, one can specify a variable
prefix component for names of the snapshot directories in the
file-system. If this parameter is set, together with the
shadow:format and shadow:delimiter parameters it determines the
possible names of snapshot directories in the file-system. The
option only supports Basic Regular Expression (BRE).
shadow:delimiter
This optional parameter is used as a delimiter between
shadow:snapprefix and shadow:format. This parameter is used only
when shadow:snapprefix is set.
Default: shadow:delimiter = "_GMT"
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 4.7 11/23/2017 VFS_SHADOW_COPY2(8)
