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>.