zfs-receive —
create snapshot from backup stream
zfs |
receive
[-FhMnsuv
]
[-o
origin=snapshot
]
[-o
property=value
]
[-x
property
]
filesystem|volume|snapshot |
zfs |
receive
[-FhMnsuv
]
[-d|-e
]
[-o
origin=snapshot
]
[-o
property=value
]
[-x
property
]
filesystem |
zfs |
receive
-A
filesystem|volume |
zfs
receive
[-FhMnsuv
]
[-o
origin=snapshot
]
[-o
property=value
]
[-x
property
]
filesystem|volume|snapshot-
zfs
receive
[-FhMnsuv
]
[-d|-e
]
[-o
origin=snapshot
]
[-o
property=value
]
[-x
property
]
filesystem- Creates a snapshot whose contents are as specified in the stream provided
on standard input. If a full stream is received, then a new file system is
created as well. Streams are created using the
zfs
send subcommand, which by default
creates a full stream. zfs
recv can be used as an alias for
zfs
receive.
If an incremental stream is received, then the destination file system must
already exist, and its most recent snapshot must match the incremental
stream's source. For zvols, the destination
device link is destroyed and recreated, which means the
zvol cannot be accessed during the
receive operation.
When a snapshot replication package stream that is generated by using the
zfs
send
-R command is received, any snapshots
that do not exist on the sending location are destroyed by using the
zfs
destroy
-d command.
The ability to send and receive deduplicated send streams has been removed.
However, a deduplicated send stream created with older software can be
converted to a regular (non-deduplicated) stream by using the
zstream
redup command.
If -o
property=value
or -x
property is specified, it applies to the
effective value of the property throughout the entire subtree of
replicated datasets. Effective property values will be set
(-o) or inherited
(-x) on the topmost in the replicated
subtree. In descendant datasets, if the property is set by the send
stream, it will be overridden by forcing the property to be inherited from
the top‐most file system. Received properties are retained in spite
of being overridden and may be restored with
zfs
inherit
-S. Specifying
-o
origin=snapshot
is a special case because, even if origin is
a read-only property and cannot be set, it's allowed to receive the send
stream as a clone of the given snapshot.
Raw encrypted send streams (created with
zfs
send
-w) may only be received as is, and
cannot be re-encrypted, decrypted, or recompressed by the receive process.
Unencrypted streams can be received as encrypted datasets, either through
inheritance or by specifying encryption parameters with the
-o options. Note that the
keylocation property cannot be overridden to
prompt during a receive. This is because the
receive process itself is already using the standard input for the send
stream. Instead, the property can be overridden after the receive
completes.
The added security provided by raw sends adds some restrictions to the send
and receive process. ZFS will not allow a mix of raw receives and non-raw
receives. Specifically, any raw incremental receives that are attempted
after a non-raw receive will fail. Non-raw receives do not have this
restriction and, therefore, are always possible. Because of this, it is
best practice to always use either raw sends for their security benefits
or non-raw sends for their flexibility when working with encrypted
datasets, but not a combination.
The reason for this restriction stems from the inherent restrictions of the
AEAD ciphers that ZFS uses to encrypt data. When using ZFS native
encryption, each block of data is encrypted against a randomly generated
number known as the "initialization vector" (IV), which is
stored in the filesystem metadata. This number is required by the
encryption algorithms whenever the data is to be decrypted. Together, all
of the IVs provided for all of the blocks in a given snapshot are
collectively called an "IV set". When ZFS performs a raw send,
the IV set is transferred from the source to the destination in the send
stream. When ZFS performs a non-raw send, the data is decrypted by the
source system and re-encrypted by the destination system, creating a
snapshot with effectively the same data, but a different IV set. In order
for decryption to work after a raw send, ZFS must ensure that the IV set
used on both the source and destination side match. When an incremental
raw receive is performed on top of an existing snapshot, ZFS will check to
confirm that the "from" snapshot on both the source and
destination were using the same IV set, ensuring the new IV set is
consistent.
The name of the snapshot (and file system, if a full stream is received)
that this subcommand creates depends on the argument type and the use of
the -d or
-e options.
If the argument is a snapshot name, the specified
snapshot is created. If the argument is a
file system or volume name, a snapshot with the same name as the sent
snapshot is created within the specified
filesystem or
volume. If neither of the
-d or
-e options are specified, the provided
target snapshot name is used exactly as provided.
The -d and
-e options cause the file system name
of the target snapshot to be determined by appending a portion of the sent
snapshot's name to the specified target
filesystem. If the
-d option is specified, all but the
first element of the sent snapshot's file system path (usually the pool
name) is used and any required intermediate file systems within the
specified one are created. If the -e
option is specified, then only the last element of the sent snapshot's
file system name (i.e. the name of the source file system itself) is used
as the target file system name.
-F- Force a rollback of the file system to the most recent snapshot before
performing the receive operation. If receiving an incremental
replication stream (for example, one generated by
zfs
send
-R
[-i|-I
]),
destroy snapshots and file systems that do not exist on the sending
side.
-d- Discard the first element of the sent snapshot's file system name,
using the remaining elements to determine the name of the target file
system for the new snapshot as described in the paragraph above.
-e- Discard all but the last element of the sent snapshot's file system
name, using that element to determine the name of the target file
system for the new snapshot as described in the paragraph above.
-h- Skip the receive of holds. There is no effect if holds are not
sent.
-M- Force an unmount of the file system while receiving a snapshot. This
option is not supported on Linux.
-n- Do not actually receive the stream. This can be useful in conjunction
with the
-v option to verify the
name the receive operation would use.
-o
origin=snapshot- Forces the stream to be received as a clone of the given snapshot. If
the stream is a full send stream, this will create the filesystem
described by the stream as a clone of the specified snapshot. Which
snapshot was specified will not affect the success or failure of the
receive, as long as the snapshot does exist. If the stream is an
incremental send stream, all the normal verification will be
performed.
-o
property=value- Sets the specified property as if the command
zfs
set
property=value
was invoked immediately before the receive. When receiving a stream
from zfs
send
-R, causes the property to be
inherited by all descendant datasets, as through
zfs
inherit
property was run on any descendant
datasets that have this property set on the sending system.
If the send stream was sent with -c
then overriding the compression property
will have no effect on received data but the
compression property will be set. To have
the data recompressed on receive remove the
-c flag from the send stream.
Any editable property can be set at receive time. Set-once properties
bound to the received data, such as
normalization and
casesensitivity, cannot be set at receive
time even when the datasets are newly created by
zfs
receive. Additionally both settable
properties version and
volsize cannot be set at receive time.
The -o option may be specified
multiple times, for different properties. An error results if the same
property is specified in multiple
-o or
-x options.
The -o option may also be used to
override encryption properties upon initial receive. This allows
unencrypted streams to be received as encrypted datasets. To cause the
received dataset (or root dataset of a recursive stream) to be
received as an encryption root, specify encryption properties in the
same manner as is required for zfs
create. For instance:
#
zfs
send
tank/test@snap1 |
zfs
recv
-o
encryption=on
-o
keyformat=passphrase
-o
keylocation=file:///path/to/keyfile
Note that -o
keylocation=prompt
may not be specified here, since the standard input is already being
utilized for the send stream. Once the receive has completed, you can
use zfs
set to change this setting after
the fact. Similarly, you can receive a dataset as an encrypted child
by specifying -x
encryption to force the property to be
inherited. Overriding encryption properties (except for
keylocation) is not possible with raw
send streams.
-s- If the receive is interrupted, save the partially received state,
rather than deleting it. Interruption may be due to premature
termination of the stream (e.g. due to network failure or failure of
the remote system if the stream is being read over a network
connection), a checksum error in the stream, termination of the
zfs
receive process, or unclean
shutdown of the system.
The receive can be resumed with a stream generated by
zfs
send
-t
token, where the
token is the value of the
receive_resume_token property of the
filesystem or volume which is received into.
To use this flag, the storage pool must have the
extensible_dataset feature enabled. See
zpool-features(7) for details on ZFS
feature flags.
-u- File system that is associated with the received stream is not
mounted.
-v- Print verbose information about the stream and the time required to
perform the receive operation.
-x
property- Ensures that the effective value of the specified property after the
receive is unaffected by the value of that property in the send stream
(if any), as if the property had been excluded from the send stream.
If the specified property is not present in the send stream, this option
does nothing.
If a received property needs to be overridden, the effective value will
be set or inherited, depending on whether the property is inheritable
or not.
In the case of an incremental update,
-x leaves any existing local
setting or explicit inheritance unchanged.
All -o restrictions (e.g. set-once)
apply equally to -x.
zfs
receive
-A
filesystem|volume- Abort an interrupted
zfs
receive
-s, deleting its saved partially
received state.
Example 1: Remotely Replicating ZFS
Data
The following commands send a full stream and then an incremental stream to a
remote machine, restoring them into
poolB/received/fs@a and
poolB/received/fs@b, respectively.
poolB must contain the file system
poolB/received, and must not initially contain
poolB/received/fs.
# zfs send pool/fs@a |
ssh host zfs receive poolB/received/fs@a
# zfs send -i a pool/fs@b |
ssh host zfs receive poolB/received/fs
Example 2: Using the
zfs
receive
-d Option
The following command sends a full stream of
poolA/fsA/fsB@snap to a remote machine,
receiving it into
poolB/received/fsA/fsB@snap. The
fsA/fsB@snap portion of the received
snapshot's name is determined from the name of the sent snapshot.
poolB must contain the file system
poolB/received. If
poolB/received/fsA does not exist, it is
created as an empty file system.
# zfs send poolA/fsA/fsB@snap |
ssh host zfs receive -d poolB/received
zfs-send(8),
zstream(8)