Ubuntu Manpage: zfs-send — generate backup stream of ZFS dataset

Provided by: zfsutils-linux_2.2.2-0ubuntu9.1_amd64

NAME

     zfs-send — generate backup stream of ZFS dataset

SYNOPSIS

     zfs send [-DLPVbcehnpsvw] [-R [-X dataset[,dataset]…]] [[-I|-i] snapshot] snapshot
     zfs send [-DLPVcensvw] [-i snapshot|bookmark] filesystem|volume|snapshot
     zfs send --redact redaction_bookmark [-DLPVcenpv] [-i snapshot|bookmark] snapshot
     zfs send [-PVenv] -t receive_resume_token
     zfs send [-PVnv] -S filesystem
     zfs redact snapshot redaction_bookmark redaction_snapshot…

DESCRIPTION

zfs send [-DLPVbcehnpsvw] [-R [-X dataset[,dataset]…]] [[-I|-i] snapshot] snapshot
Creates a stream representation of the second snapshot, which is written to standard
output. The output can be redirected to a file or to a different system (for example,
using ssh(1)). By default, a full stream is generated.

-D, --dedup
Deduplicated send is no longer supported. This flag is accepted for backwards
compatibility, but a regular, non-deduplicated stream will be generated.

-I snapshot
Generate a stream package that sends all intermediary snapshots from the first
snapshot to the second snapshot. For example, -I @a fs@d is similar to -i @a fs@b; -i
@b fs@c; -i @c fs@d. The incremental source may be specified as with the -i option.

-L, --large-block
Generate a stream which may contain blocks larger than 128 KiB. This flag has no
effect if the large_blocks pool feature is disabled, or if the recordsize property of
this filesystem has never been set above 128 KiB. The receiving system must have the
large_blocks pool feature enabled as well. See zpool-features(7) for details on ZFS
feature flags and the large_blocks feature.

-P, --parsable
Print machine-parsable verbose information about the stream package generated.

-R, --replicate
Generate a replication stream package, which will replicate the specified file system,
and all descendent file systems, up to the named snapshot. When received, all
properties, snapshots, descendent file systems, and clones are preserved.

If the -i or -I flags are used in conjunction with the -R flag, an incremental
replication stream is generated. The current values of properties, and current
snapshot and file system names are set when the stream is received. If the -F flag is
specified when this stream is received, snapshots and file systems that do not exist
on the sending side are destroyed. If the -R flag is used to send encrypted datasets,
then -w must also be specified.

-V, --proctitle
Set the process title to a per-second report of how much data has been sent.

-X, --exclude dataset[,dataset]…
With -R, -X specifies a set of datasets (and, hence, their descendants), to be
excluded from the send stream. The root dataset may not be excluded. -X a -X b is
equivalent to -X a,b.

-e, --embed
Generate a more compact stream by using WRITE_EMBEDDED records for blocks which are
stored more compactly on disk by the embedded_data pool feature. This flag has no
effect if the embedded_data feature is disabled. The receiving system must have the
embedded_data feature enabled. If the lz4_compress feature is active on the sending
system, then the receiving system must have that feature enabled as well. Datasets
that are sent with this flag may not be received as an encrypted dataset, since
encrypted datasets cannot use the embedded_data feature. See zpool-features(7) for
details on ZFS feature flags and the embedded_data feature.

-b, --backup
Sends only received property values whether or not they are overridden by local
settings, but only if the dataset has ever been received. Use this option when you
want zfs receive to restore received properties backed up on the sent dataset and to
avoid sending local settings that may have nothing to do with the source dataset, but
only with how the data is backed up.

-c, --compressed
Generate a more compact stream by using compressed WRITE records for blocks which are
compressed on disk and in memory (see the compression property for details). If the
lz4_compress feature is active on the sending system, then the receiving system must
have that feature enabled as well. If the large_blocks feature is enabled on the
sending system but the -L option is not supplied in conjunction with -c, then the data
will be decompressed before sending so it can be split into smaller block sizes.
Streams sent with -c will not have their data recompressed on the receiver side using
-o compress= value. The data will stay compressed as it was from the sender. The new
compression property will be set for future data. Note that uncompressed data from
the sender will still attempt to compress on the receiver, unless you specify -o
compress= off.

-w, --raw
For encrypted datasets, send data exactly as it exists on disk. This allows backups
to be taken even if encryption keys are not currently loaded. The backup may then be
received on an untrusted machine since that machine will not have the encryption keys
to read the protected data or alter it without being detected. Upon being received,
the dataset will have the same encryption keys as it did on the send side, although
the keylocation property will be defaulted to prompt if not otherwise provided. For
unencrypted datasets, this flag will be equivalent to -Lec. Note that if you do not
use this flag for sending encrypted datasets, data will be sent unencrypted and may be
re-encrypted with a different encryption key on the receiving system, which will
disable the ability to do a raw send to that system for incrementals.

-h, --holds
Generate a stream package that includes any snapshot holds (created with the zfs hold
command), and indicating to zfs receive that the holds be applied to the dataset on
the receiving system.

-i snapshot
Generate an incremental stream from the first snapshot (the incremental source) to the
second snapshot (the incremental target). The incremental source can be specified as
the last component of the snapshot name (the @ character and following) and it is
assumed to be from the same file system as the incremental target.

If the destination is a clone, the source may be the origin snapshot, which must be
fully specified (for example, pool/fs@origin, not just @origin).

-n, --dryrun
Do a dry-run ("No-op") send. Do not generate any actual send data. This is useful in
conjunction with the -v or -P flags to determine what data will be sent. In this
case, the verbose output will be written to standard output (contrast with a
non-dry-run, where the stream is written to standard output and the verbose output
goes to standard error).

-p, --props
Include the dataset's properties in the stream. This flag is implicit when -R is
specified. The receiving system must also support this feature. Sends of encrypted
datasets must use -w when using this flag.

-s, --skip-missing
Allows sending a replication stream even when there are snapshots missing in the
hierarchy. When a snapshot is missing, instead of throwing an error and aborting the
send, a warning is printed to the standard error stream and the dataset to which it
belongs and its descendents are skipped. This flag can only be used in conjunction
with -R.

-v, --verbose
Print verbose information about the stream package generated. This information
includes a per-second report of how much data has been sent. The same report can be
requested by sending SIGINFO or SIGUSR1, regardless of -v.

The format of the stream is committed. You will be able to receive your streams on
future versions of ZFS.

zfs send [-DLPVcenvw] [-i snapshot|bookmark] filesystem|volume|snapshot
Generate a send stream, which may be of a filesystem, and may be incremental from a
bookmark. If the destination is a filesystem or volume, the pool must be read-only, or
the filesystem must not be mounted. When the stream generated from a filesystem or volume
is received, the default snapshot name will be "--head--".

-D, --dedup
Deduplicated send is no longer supported. This flag is accepted for backwards
compatibility, but a regular, non-deduplicated stream will be generated.

-P, --parsable
Print machine-parsable verbose information about the stream package generated.

-i snapshot|bookmark
Generate an incremental send stream. The incremental source must be an earlier
snapshot in the destination's history. It will commonly be an earlier snapshot in the
destination's file system, in which case it can be specified as the last component of
the name (the # or @ character and following).

If the incremental target is a clone, the incremental source can be the origin
snapshot, or an earlier snapshot in the origin's filesystem, or the origin's origin,
etc.

zfs send --redact redaction_bookmark [-DLPVcenpv] [-i snapshot|bookmark] snapshot
Generate a redacted send stream. This send stream contains all blocks from the snapshot
being sent that aren't included in the redaction list contained in the bookmark specified
by the --redact (or -d) flag. The resulting send stream is said to be redacted with
respect to the snapshots the bookmark specified by the --redact flag was created with.
The bookmark must have been created by running zfs redact on the snapshot being sent.

This feature can be used to allow clones of a filesystem to be made available on a remote
system, in the case where their parent need not (or needs to not) be usable. For example,
if a filesystem contains sensitive data, and it has clones where that sensitive data has
been secured or replaced with dummy data, redacted sends can be used to replicate the
secured data without replicating the original sensitive data, while still sharing all
possible blocks. A snapshot that has been redacted with respect to a set of snapshots
will contain all blocks referenced by at least one snapshot in the set, but will contain
none of the blocks referenced by none of the snapshots in the set. In other words, if all
snapshots in the set have modified a given block in the parent, that block will not be
sent; but if one or more snapshots have not modified a block in the parent, they will
still reference the parent's block, so that block will be sent. Note that only user data
will be redacted.

When the redacted send stream is received, we will generate a redacted snapshot. Due to
the nature of redaction, a redacted dataset can only be used in the following ways:

1. To receive, as a clone, an incremental send from the original snapshot to one of the
snapshots it was redacted with respect to. In this case, the stream will produce a
valid dataset when received because all blocks that were redacted in the parent are
guaranteed to be present in the child's send stream. This use case will produce a
normal snapshot, which can be used just like other snapshots.

2. To receive an incremental send from the original snapshot to something redacted with
respect to a subset of the set of snapshots the initial snapshot was redacted with
respect to. In this case, each block that was redacted in the original is still
redacted (redacting with respect to additional snapshots causes less data to be
redacted (because the snapshots define what is permitted, and everything else is
redacted)). This use case will produce a new redacted snapshot.

3. To receive an incremental send from a redaction bookmark of the original snapshot that
was created when redacting with respect to a subset of the set of snapshots the
initial snapshot was created with respect to anything else. A send stream from such a
redaction bookmark will contain all of the blocks necessary to fill in any redacted
data, should it be needed, because the sending system is aware of what blocks were
originally redacted. This will either produce a normal snapshot or a redacted one,
depending on whether the new send stream is redacted.

4. To receive an incremental send from a redacted version of the initial snapshot that is
redacted with respect to a subject of the set of snapshots the initial snapshot was
created with respect to. A send stream from a compatible redacted dataset will
contain all of the blocks necessary to fill in any redacted data. This will either
produce a normal snapshot or a redacted one, depending on whether the new send stream
is redacted.

5. To receive a full send as a clone of the redacted snapshot. Since the stream is a
full send, it definitionally contains all the data needed to create a new dataset.
This use case will either produce a normal snapshot or a redacted one, depending on
whether the full send stream was redacted.

These restrictions are detected and enforced by zfs receive; a redacted send stream will
contain the list of snapshots that the stream is redacted with respect to. These are
stored with the redacted snapshot, and are used to detect and correctly handle the cases
above. Note that for technical reasons, raw sends and redacted sends cannot be combined
at this time.

zfs send [-PVenv] -t receive_resume_token
Creates a send stream which resumes an interrupted receive. The receive_resume_token is
the value of this property on the filesystem or volume that was being received into. See
the documentation for zfs receive -s for more details.

zfs send [-PVnv] [-i snapshot|bookmark] -S filesystem
Generate a send stream from a dataset that has been partially received.

-S, --saved
This flag requires that the specified filesystem previously received a resumable send
that did not finish and was interrupted. In such scenarios this flag enables the user
to send this partially received state. Using this flag will always use the last fully
received snapshot as the incremental source if it exists.

zfs redact snapshot redaction_bookmark redaction_snapshot…
Generate a new redaction bookmark. In addition to the typical bookmark information, a
redaction bookmark contains the list of redacted blocks and the list of redaction
snapshots specified. The redacted blocks are blocks in the snapshot which are not
referenced by any of the redaction snapshots. These blocks are found by iterating over
the metadata in each redaction snapshot to determine what has been changed since the
target snapshot. Redaction is designed to support redacted zfs sends; see the entry for
zfs send for more information on the purpose of this operation. If a redact operation
fails partway through (due to an error or a system failure), the redaction can be resumed
by rerunning the same command.

Redaction
ZFS has support for a limited version of data subsetting, in the form of redaction. Using
the zfs redact command, a redaction bookmark can be created that stores a list of blocks
containing sensitive information. When provided to zfs send, this causes a redacted send to
occur. Redacted sends omit the blocks containing sensitive information, replacing them with
REDACT records. When these send streams are received, a redacted dataset is created. A
redacted dataset cannot be mounted by default, since it is incomplete. It can be used to
receive other send streams. In this way datasets can be used for data backup and
replication, with all the benefits that zfs send and receive have to offer, while protecting
sensitive information from being stored on less-trusted machines or services.

For the purposes of redaction, there are two steps to the process. A redact step, and a
send/receive step. First, a redaction bookmark is created. This is done by providing the
zfs redact command with a parent snapshot, a bookmark to be created, and a number of
redaction snapshots. These redaction snapshots must be descendants of the parent snapshot,
and they should modify data that is considered sensitive in some way. Any blocks of data
modified by all of the redaction snapshots will be listed in the redaction bookmark, because
it represents the truly sensitive information. When it comes to the send step, the send
process will not send the blocks listed in the redaction bookmark, instead replacing them
with REDACT records. When received on the target system, this will create a redacted
dataset, missing the data that corresponds to the blocks in the redaction bookmark on the
sending system. The incremental send streams from the original parent to the redaction
snapshots can then also be received on the target system, and this will produce a complete
snapshot that can be used normally. Incrementals from one snapshot on the parent filesystem
and another can also be done by sending from the redaction bookmark, rather than the
snapshots themselves.

In order to make the purpose of the feature more clear, an example is provided. Consider a
zfs filesystem containing four files. These files represent information for an online
shopping service. One file contains a list of usernames and passwords, another contains
purchase histories, a third contains click tracking data, and a fourth contains user
preferences. The owner of this data wants to make it available for their development teams
to test against, and their market research teams to do analysis on. The development teams
need information about user preferences and the click tracking data, while the market
research teams need information about purchase histories and user preferences. Neither
needs access to the usernames and passwords. However, because all of this data is stored in
one ZFS filesystem, it must all be sent and received together. In addition, the owner of
the data wants to take advantage of features like compression, checksumming, and snapshots,
so they do want to continue to use ZFS to store and transmit their data. Redaction can help
them do so. First, they would make two clones of a snapshot of the data on the source. In
one clone, they create the setup they want their market research team to see; they delete
the usernames and passwords file, and overwrite the click tracking data with dummy
information. In another, they create the setup they want the development teams to see, by
replacing the passwords with fake information and replacing the purchase histories with
randomly generated ones. They would then create a redaction bookmark on the parent
snapshot, using snapshots on the two clones as redaction snapshots. The parent can then be
sent, redacted, to the target server where the research and development teams have access.
Finally, incremental sends from the parent snapshot to each of the clones can be sent to and
received on the target server; these snapshots are identical to the ones on the source, and
are ready to be used, while the parent snapshot on the target contains none of the username
and password data present on the source, because it was removed by the redacted send
operation.

SIGNALS

     See -v.

EXAMPLES

   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

NAME

SYNOPSIS

DESCRIPTION

SIGNALS

EXAMPLES

SEE ALSO