vfs_shadow_copy2 — Expose snapshots to Windows clients as shadow copies.
vfs objects = shadow_copy2
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.
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
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
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
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.
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
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
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
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"
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
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
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
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
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).
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"
Add shadow copy support to user home directories:
[homes]
vfs objects = shadow_copy2
shadow:snapdir = /data/snapshots
shadow:basedir = /data/home
shadow:sort = desc
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.