NAME

zfs-send — generate backup stream of ZFS dataset

SYNOPSIS

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.

-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.

-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.

-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.

-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.

-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.

-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).

-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.

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.

SIGNALS

See -v.

EXAMPLES

# 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

# zfs send poolA/fsA/fsB@snap |
    ssh host zfs receive -d poolB/received

SEE ALSO

zfs-bookmark(8), zfs-receive(8), zfs-redact(8), zfs-snapshot(8)