vfs_shadow_copy2
8
Samba
System Administration tools
4.3
vfs_shadow_copy2
Expose snapshots to Windows clients as shadow copies.
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):
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].
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.
Vanity naming for snapshots: snapshots can be named in any format
compatible with str[fp]time conversions.
Timestamps can be represented in localtime rather than UTC.
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.
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:
shadow_copy2
/data/snapshots
/data/home
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.