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bup-split

NAME

bup-split - save individual files to bup backup sets

SYNOPSIS

bup split [-r host:path] <-b|-t|-c|-n name> [-v] [-q] [---bench] [---max-pack-size=bytes] [---max-pack-objects=n] [---fanout=*count] [filenames...]

DESCRIPTION

bup split concatenates the contents of the given files (or if no filenames are given, reads from stdin), splits the content into chunks of around 8k using a rolling checksum algorithm, and saves the chunks into a bup repository. Chunks which have previously been stored are not stored again (ie. they are "deduplicated").

Because of the way the rolling checksum works, chunks tend to be very stable across changes to a given file, including adding, deleting, and changing bytes.

For example, if you use bup split to back up an XML dump of a database, and the XML file changes slightly from one run to the next, nearly all the data will still be deduplicated and the size of each backup after the first will typically be quite small.

Another technique is to pipe the output of the tar(1) or cpio(1) programs to bup split. When individual files in the tarball change slightly or are added or removed, bup still processes the remainder of the tarball efficiently. (Note that bup save is usually a more efficient way to accomplish this, however.)

To get the data back, use bup-join(1).

OPTIONS

-r, ---remote=host:path

save the backup set to the given remote server. If path is omitted, uses the default path on the remote server (you still need to include the ':')

-b, ---blobs

output a series of git blob ids that correspond to the chunks in the dataset.

-t, ---tree

output the git tree id of the resulting dataset.

-c, ---commit

output the git commit id of the resulting dataset.

-n, ---name=name

after creating the dataset, create a git branch named name so that it can be accessed using that name. If name already exists, the new dataset will be considered a descendant of the old name. (Thus, you can continually create new datasets with the same name, and later view the history of that dataset to see how it has changed over time.)

-v, ---verbose

increase verbosity (can be used more than once).

-q, ---quiet

disable progress messages.

---bench

print benchmark timings to stderr.

---max-pack-size=bytes

never create git packfiles larger than the given number of bytes. Default is 1 billion bytes. Usually there is no reason to change this.

---max-pack-objects=numobjs

never create git packfiles with more than the given number of objects. Default is 200 thousand objects. Usually there is no reason to change this.

---fanout=numobjs

when splitting very large files, never put more than this number of git blobs in a single git tree. Instead, generate a new tree and link to that. Default is 4096 objects per tree.

EXAMPLE

      $ tar -cf - /etc | bup split -r myserver: -n mybackup-tar
      tar: Removing leading /' from member names
      Indexing objects: 100% (196/196), done.
      
      $ bup join -r myserver: mybackup-tar | tar -tf - | wc -l
      1961

SEE ALSO

bup-join(1), bup-index(1), bup-save(1)

BUP

Part of the bup(1) suite.

AUTHORS

Avery Pennarun <apenwarr@gmail.com>.