The send operation compares two subvolumes and writes a description of how to convert one subvolume (the parent subvolume) into the other (the sent subvolume). You would usually direct the output to a file for later use or pipe it to a receive operation for immediate use.

The simplest form of the send operation writes a complete description of a subvolume:

# btrfs send [-v] [-f sent_file] ... subvol

You can specify multiple instances of the -v option to display increasing amounts of debugging output. The -f option allows you to save the output to a file. Both of these options are implicit in the following usage examples.

The following form of the send operation writes a complete description of how to convert one subvolume into another:

# btrfs send -p parent_subvol sent_subvol

If a subvolume such as a snapshot of the parent volume, known as a clone source, will be available during the receive operation from which some of the data can be recovered, you can specify the clone source to reduce the size of the output file:

# btrfs send [-p parent_subvol] -c clone_src [-c clone_src] ... subvol

You can specify the -c option multiple times if there is more than one clone source. If you do not specify the parent subvolume, btrfs chooses a suitable parent from the clone sources.

You use the receive operation to regenerate the sent subvolume at a specified path:

# btrfs receive [-f sent_file] mountpoint