VFS_SHADOW_COPY2(8) System Administration tools VFS_SHADOW_COPY2(8)

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:

+o YYYY is the 4 digit year

+o MM is the 2 digit month

+o DD is the 2 digit day

+o hh is the 2 digit hour

+o mm is the 2 digit minute

+o 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

+o basedir = mountpoint/rel_basedir

+o share_root = basedir/rel_share_root

+o 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:

+o share1/

+o share2/

+o .../

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 part of version 4.18.11 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 4.18.11 03/13/2024 VFS_SHADOW_COPY2(8)