path: root/rdiff-backup/rdiff-backup.1

.TH RDIFF-BACKUP 1 "AUGUST 2001" "Version 0.2.1" "User Manuals" \" -*- nroff -*-
.SH NAME
rdiff-backup \- local/remote mirror and incremental backup
.SH SYNOPSIS
.B rdiff-backup
.BI [ options ]
.BI [[[ user@ ] host1.foo ]:: source_directory ]
.BI [[[ user@ ] host2.foo ]:: destination_directory ]

.B rdiff-backup
.B {{ -l | --list-increments }
.BI "| --remove-older-than " time_interval }
.BI [[[ user@ ] host2.foo ]:: destination_directory ]

.B rdiff-backup --calculate-average
.I statfile1 statfile2 ...

.SH DESCRIPTION
.B rdiff-backup
is a script, written in
.BR python (1)
that backs up one directory to another.  The target directory ends up
a copy of the source directory, but extra reverse diffs are stored in
the target directory, so you can still recover files lost some time
ago.  The idea is to combine the best features of a mirror and an
incremental backup.  rdiff-backup also preserves symlinks, special
files, hardlinks, permissions, uid/gid ownership (if it is running as
root), and modification times.

.B rdiff-backup
can also operate
in a bandwidth efficient manner over a pipe, like
.BR rsync (1).
Thus you can use ssh and rdiff-backup to securely back a hard drive up
to a remote location, and only the differences will be transmitted.
Using the default settings, rdiff-backup requires that the remote
system accept ssh connections, and that
.B rdiff-backup
is installed in the user's PATH on the remote system.  For information
on other options, see the section on
.B REMOTE OPERATION.


.SH OPTIONS
.TP
.B -b, --backup-mode
Force backup mode even if first argument appears to be an increment file.
.TP
.B --calculate-average
Enter calculate average mode.  The arguments should be a number of
statistics files.  rdiff-backup will print the average of the listed
statistics files and exit.
.TP
.B --change-source-perms
If this option is set, rdiff-backup will try to change the mode of any
unreadable files or unreadable/unexecutable directories in the source
directory so it can back them up.  It will then restore their original
permissions and mtimes afterwards.  This option should generally not
be used if rdiff-backup has root access to the source directory, as
root can access files regardless of their permissions.
.TP
.BI "--chars-to-quote " chars
If this option is set, any characters in
.I chars
present in filenames on the source side will be quoted on the
destination side, so that they do not appear in filenames on the
remote side.  See
.B --quoting-char
and
.BR --windows-mode .
.TP
.BI "--checkpoint-interval " seconds
This option controls every how many seconds rdiff-backup checkpoints
its current status.  The default is 20.
.TP
.BI "--current-time " seconds
This option is useful mainly for testing.  If set, rdiff-backup will
it for the current time instead of consulting the clock.  The argument
is the number of seconds since the epoch.
.TP
.BI "--exclude " shell_pattern
Exclude the file or files matched by
.IR shell_pattern .
If a directory is matched, then files under that directory will also
be matched.  See the
.B FILE SELECTION
section for more information.
.TP
.B "--exclude-device-files"
Exclude all device files.  This can be useful for security/permissions
reasons or if rdiff-backup is not handling device files correctly.
.TP
.BI "--exclude-filelist " filename
Excludes the files listed in 
.I filename
See the
.B FILE SELECTION
section for more information.
.TP
.B --exclude-filelist-stdin
Like
.B --exclude-filelist,
but the list of files will be read from standard input.  See the
.B FILE SELECTION
section for more information.
.TP
.BI "--exclude-mirror " regexp
Exclude files in the mirror area matching regexp.  This argument can
be used multiple times.  The rdiff-backup-data directory is
automatically excluded, so this option rarely needs to be used.
.TP
.B --exclude-other-filesystems
Exclude files on file systems (identified by device number) other than
the file system the root of the source directory is on.
.TP
.BI "--exclude-regexp " regexp
Exclude files matching the given regexp.  Unlike the
.B --exclude
option, this option does not match files in a directory it matches.
See the
.B FILE SELECTION
section for more information.
.TP
.B --force
Authorize overwriting of a destination directory.  rdiff-backup will
generally tell you if it needs this.
.TP
.BI "--include " shell_pattern
Similar to
.B --exclude
but include matched files instead.  Unlike
.BR --exclude ,
this option will also match parent directories of matched files
(although not necessarily their contents).  See the
.B FILE SELECTION
section for more information.
.TP
.BI "--include-filelist " filename
Like
.BR --exclude-filelist ,
but include the listed files instead.  See the
.B FILE SELECTION
section for more information.
.TP
.B --include-filelist-stdin
Like
.BR --include-filelist ,
but read the list of included files from standard input.
.TP
.BI "--include-regexp " regexp
Include files matching the regular expression
.IR regexp .
Only files explicitly matched by
.I regexp
will be included by this option.  See the
.B FILE SELECTION
section for more information.
.TP
.B "-l, --list-increments"
List the number and date of partial incremental backups contained in
the specified destination directory.  This option is incompatible with
backing up or restoring and must be run in a separate instance of
rdiff-backup.
.TP
.B "-m, --mirror-only"
Do not create an rdiff-backup-data directory or make any increments.
In this mode rdiff-backup is similar to rsync (but usually
slower).
.TP
.B --no-compression
Disable the default gzip compression of most of the .snapshot and .diff
increment files stored in the rdiff-backup-data directory.  A backup
volume can contain compressed and uncompressed increments, so using
this option inconsistently is fine.
.TP
.B "--no-compression-regexp " regexp
Do not compress increments based on files whose filenames match regexp.
The default is
"(?i).*\\.(gz|z|bz|bz2|tgz|zip|rpm|deb|jpg|gif|png|jp2|mp3|ogg|avi|wmv|mpeg|mpg|rm|mov)$"
.TP
.BI --no-hard-links
Don't preserve hard links from source to mirror directories.
Otherwise, no increment files will themselves be hard linked, but a
hard link database will be written so that hard links from any dataset
will be recreated if originally present.  If many hard linked files
are present, this option can drastically decrease memory usage.
.TP
.B --no-resume
Do not resume last aborted backup even if it falls within the resume
window.
.TP
.B --null-separator
Use nulls (\\0) instead of newlines (\\n) as line separators, which
may help when dealing with filenames containing newlines.  This
affects the expected format of the files specified by the
--{include|exclude}-filelist[-stdin] switches as well as the format of
the directory_statistics file.
.TP
.B --parsable-output
If set, rdiff-backup's output will be tailored for easy parsing by
computers, instead of clarity for humans.  Currently this only applies
when listing increments using the
.B -l
or
.B --list-increments
switches.
.TP
.B --print-statistics
If set, summary statistics will be printed after a successful backup
If not set, this information will still be available from the
session_statistics.<time>.data file.
.TP
.BI "--quoting-char " char
Use the specified character for quoting characters specified to be
escaped by the
.B --chars-to-quote
option.  The default is the semicolon ";".  See also
.BR --windows-mode .
.TP
.BI "-r, --restore-as-of " restore_time
Restore the specified directory as it was as of
.IR restore_time .
See the
.B TIME FORMATS
section for more information on the format of
.IR restore_time ,
and see the
.B RESTORING
section for more information on restoring.
.TP
.BI "--remote-cmd " command
This command has been depreciated as of version 0.4.1.  Use
--remote-schema instead.
.TP
.BI "--remote-schema " schema
Specify an alternate method of connecting to a remote computer.  This
is necessary to get rdiff-backup not to use ssh for remote backups, or
if, for instance, rdiff-backup is not in the PATH on the remote side.
See the
.B REMOTE OPERATION
section for more information.
.TP
.BI "--remove-older-than " time_spec
Remove the incremental backup information in the destination directory
that has been around longer than the given time.
.I time_spec
can be either an absolute time, like "2002-01-04", or a time interval.
The time interval is an integer followed by the character s, m, h, D,
W, M, or Y, indicating seconds, minutes, hours, days, weeks, months,
or years respectively, or a number of these concatenated.  For
example, 32m means 32 minutes, and 3W2D10h7s means 3 weeks, 2 days, 10
hours, and 7 seconds.  In this context, a month means 30 days, a year
is 365 days, and a day is always 86400 seconds.

Note that this option is incompatible with backing up or restoring and
must be run in a separate instance of rdiff-backup.  Remember also
that snapshots of deleted files are covered by this operation, so if
you deleted a file and backed up two weeks ago, and then run
--remove-older-than 10D today, no trace of that file will remain.
.TP
.BI "--restrict " path
Require that all file access be inside the given path.  This switch,
and the following two, are intended to be used with the --server
switch to provide a bit more protection when doing automated remote
backups.  They are
.B not intended as your only line of defense
so please don't do something silly like allow public access to an
rdiff-backup server run with --restrict-read-only.
.TP
.BI "--restrict-read-only " path
Like
.BR --restrict ,
but also reject all write requests.
.TP
.BI "--restrict-update-only " path
Like
.BR --restrict ,
but only allow writes as part of an incremental backup.  Requests for other types of writes (for instance, deleting 
.IR path )
will be rejected.
.TP
.B --resume
Resume the last aborted backup.  If no aborted backups are found, exit
with error.
.TP
.BI "--resume-window " seconds
Resume the last aborted backup if it started less than the specified
number of seconds ago.  Otherwise start a new backup.  The default is
7200 (2 hours).
.TP
.B --server
Enter server mode (not to be invoked directly, but instead used by
another rdiff-backup process on a remote computer).
.TP
.BI "--sleep-ratio " ratio
Here ratio should be between 0 and 1 not inclusive.  When backing up
rdiff-backup will try to spend that ratio of time just sleeping.  For
example, if --sleep-ratio 0.33 is specified, rdiff-backup will spent
about a third of the time asleep, just sitting there.  This can be
helpful if rdiff-backup would normally push some resource too hard.
.TP
.B --ssh-no-compression
When running ssh, do not use the -C option to enable compression.
.B --ssh-no-compression
is ignored if you specify a new schema using
.B --remote-schema.
.TP
.BI "--terminal-verbosity " [0-9]
Select which messages will be displayed to the terminal.  If missing
the level defaults to the verbosity level.
.TP
.B --test-server
Test for the presence of a compatible rdiff-backup server as specified
in the following host::filename argument(s).  The filename section
will be ignored.
.TP
.BI -v [0-9] ", --verbosity " [0-9]
Specify verbosity level (0 is totally silent, 3 is the default, and 9
is noisiest).  This determines how much is written to the log file.
.TP
.B "-V, --version"
Print the current version and exit
.TP
.B --windows-mode
This option is short for "--chars to quote : --windows-time-format"
and is appropriate when backing up to a filesystem that doesn't allow
colons in filenames.
.TP
.B --windows-time-format
If this option is present, use underscores instead of colons in
increment files, so 2001-07-15T04:09:38-07:00 becomes
2001-07-15T04_09_38-07_00.  This option may be useful under MS windows
NT, which prohibits colons in filenames.

.SH EXAMPLES
Simplest case---backup directory foo to directory bar, with increments
in bar/rdiff-backup-data:
.PP
.RS
rdiff-backup foo bar
.PP
.RE
This is exactly the same as previous example because trailing slashes
are ignored:
.PP
.RS
rdiff-backup foo/ bar/
.PP
.RE
Back files up from /home/bob to /mnt/backup, leaving increments in /mnt/backup/rdiff-backup-data.  Do not back up directory /home/bob/tmp or any files in it.
.PP
.RS
rdiff-backup --exclude /home/bob/tmp /home/bob /mnt/backup
.PP
.RE
The file selection options can be combined in various ways.  The
following command backs up the whole file system to /usr/local/backup.
However, the entire /usr directory is skipped, with the exception of
/usr/local, which is included, except for /usr/local/backup, which is
excluded to prevent a circularity:
.PP
.RS
rdiff-backup --exclude /usr/local/backup --include /usr/local --exclude /usr / /usr/local/backup
.PP
.RE
You can also use regular expressions in the --exclude statements.
This will skip any files whose full pathnames contain the word
"cache", or any files whose name is "tmp", "temp", "TMP", "tEmP", etc.
.PP
.RS
rdiff-backup --exclude-regexp cache --exclude-regexp '(?i)/te?mp$' /home/bob /mnt/backup
.PP
.RE
After the previous command was completed, this command will list the
backups present on the destination disk:
.PP
.RS
rdiff-backup --list-increments /mnt/backup
.PP
.RE
If space is running out on the /mnt/backup directory, older
incremental backups can be erased.  The following command erases
backup information older than a week:
.PP
.RS
rdiff-backup --remove-older-than 7D /mnt/backup
.PP
.RE
The following reads the file
important-data.2001-07-15T04:09:38-07:00.dir and restores the
resulting directory important-data as it was on Februrary 14, 2001,
calling the new directory "temp".  Note that rdiff-backup goes into
restore mode because it recognizes the suffix of the file.  The -v9
means keep lots of logging information.
.PP
.RS
rdiff-backup -v9 important-data.2001-07-15T04:09:38-07:00.dir temp
.PP
.RE
This command causes rdiff-backup to backup the directory
/some/local-dir to the directory /whatever/remote-dir on the machine
hostname.net.  It uses ssh to open the necessary pipe to the remote
copy of rdiff-backup.  Here the username on the local machine and on
hostname.net are the same.
.PP
.RS
rdiff-backup /some/local-dir hostname.net::/whatever/remote-dir
.PP
.RE
This command logs into hostname.net as smith and restores the remote
increment old-file on a remote computer to the current directory on
the local computer:
.PP
.RS
rdiff-backup smith@hostname.net::/foo/rdiff-backup-data/increments/bar/old-file.2001-11-09T12:43:53-04:00.diff
.PP
.RE
Backup foo on one remote machine to bar on another.  This will
probably be slower than running rdiff-backup from either machine.
.PP
.RS
rdiff-backup smith@host1::foo jones@host2::bar
.PP
.RE
Test to see if the specified ssh command really opens up a working
rdiff-backup server on the remote side.
.RS
rdiff-backup --test-server hostname.net::/this/is/ignored

.SH RESTORING
There are two ways to tell rdiff-backup to restore a file or
directory.  Firstly, you can run rdiff-backup on a mirror file and use
the
.B -r
or
.B --restore-as-of
options.  Secondly, you can run it on an increment file.
.PP
For example, suppose in the past you have run:
.PP
.RS
rdiff-backup /usr /usr.backup
.PP
.RE
to back up the /usr directory into the /usr.backup directory, and now
want a copy of the /usr/local directory the way it was 3 days ago
placed at /usr/local.old.
.PP
One way to do this is to run:
.PP
.RS
rdiff-backup -r 3D /usr.backup/local /usr/local.old
.PP
.RE
where above the "3D" means 3 days (for other ways to specify the time,
see the
.B TIME FORMATS
section).  The /usr.backup/local directory was selected, because that
is the directory containing the current version of /usr/local.
.PP
The second way to do this would be to find the corresponding increment
file.  It would be in the /backup/rdiff-backup-data/increments/usr
directory, and its name would be something like
"local.2002-11-09T12:43:53-04:00.dir" where the time indicates it is
from 3 days ago.  Note that the increment files all end in ".diff",
".snapshot", ".dir", or ".missing", where ".missing" just means that
the file didn't exist at that time (finally, some of these may be
gzip-compressed, and have an extra ".gz" to indicate this).  Then
running:
.PP
.RS
rdiff-backup /backup/rdiff-backup-data/increments/usr/local.<time>.dir /usr/local.old
.PP
.RE
would also restore the file as desired.

.SH TIME FORMATS
rdiff-backup uses time strings in two places.  Firstly, all of the
increment files rdiff-backup creates will have the time in their
filenames in the w3 datetime format as described in a w3 note at
http://www.w3.org/TR/NOTE-datetime.  Basically they look like
"2001-07-15T04:09:38-07:00", which means what it looks like.  The
"-07:00" section means the time zone is 7 hours behind UTC.
.PP
Secondly, the
.BI -r , " --restore-as-of" ", and " --remove-older-than
options take a time string, which can be given in any of several
formats:
.IP 1.
the string "now" (refers to the current time)
.IP 2.
a sequences of digits, like "123456890" (indicating the time in
seconds after the epoch)
.IP 3.
A string like "2002-01-25T07:00:00+02:00" in datetime format 
.IP 4.
An interval, which is a number followed by one of the characters s, m,
h, D, W, M, or Y (indicating seconds, minutes, hourse, days, weeks,
months, or years respectively), or a series of such pairs.  In this
case the string refers to the time that preceded the current time by
the length of the interval.  For instance, "1h78m" indicates the time
that was one hour and 78 minutes ago.  The calendar here is
unsophisticated: a month is always 30 days, a year is always 365 days,
and a day is always 86400 seconds.
.IP 5.
A date format of the form YYYY/MM/DD, YYYY-MM-DD, MM/DD/YYYY, or
MM/DD/YYYY, which indicates midnight on the day in question, relative
to the current timezone settings.  For instance, "2002/3/5",
"03-05-2002", and "2002-3-05" all mean March 5th, 2002.

.SH REMOTE OPERATION
In order to access remote files, rdiff-backup opens up a pipe to a
copy of rdiff-backup running on the remote machine.  Thus rdiff-backup
must be installed on both ends.  To open this pipe, rdiff-backup first
splits the filename into host_info::pathname.  It then substitutes
host_info into the remote schema, and runs the resulting command,
reading its input and output.
.PP
The default remote schema is 'ssh %s rdiff-backup --server' meaning if
the host_info is user@host.net, then rdiff-backup runs 'ssh
user@host.net rdiff-backup --server'.  The '%s' keyword is substituted
with the host_info.  Using --remote-schema, rdiff-backup can invoke an
arbitrary command in order to open up a remote pipe.  For instance,
.RS
rdiff-backup --remote-schema 'cd /usr; %s' foo 'rdiff-backup
--server'::bar
.RE
is basically equivalent to (but slower than)
.RS
rdiff-backup foo /usr/bar
.RE
.PP
Concerning quoting, if for some reason you need to put two consecutive
colons in the host_info section of a host_info::pathname argument, or
in the pathname of a local file, you can quote one of them by
prepending a backslash.  So in 'a\\::b::c', host_info is 'a::b' and
the pathname is 'c'.  Similarly, if you want to refer to a local file
whose filename contains two consecutive colons, like 'strange::file',
you'll have to quote one of the colons as in 'strange\\::file'.
Because the backslash is a quote character in these circumstances, it
too must be quoted to get a literal backslash, so 'foo\\::\\\\bar'
evaluates to 'foo::\\bar'.  To make things more complicated, because
the backslash is also a common shell quoting character, you may need
to type in '\\\\\\\\' at the shell prompt to get a literal backslash
(if it makes you feel better, I had to type in 8 backslashes to get
that in this man page...).  And finally, to include a literal % in the
string specified by --remote-schema, quote it with another %, as in
%%.

.SH FILE SELECTION
.B rdiff-backup
supports file selection options similar to (but different from)
.BR rsync (1).
The system may appear complicated, but it is supposed to be flexible
and easy-to-use.

When rdiff-backup is run, it searches through the given source
directory and backs up all the files specified by the file selection
system.  The file selection system comprises a number of file
selection conditions, which are set using one of the following command
line options:
.BR --exclude ,
.BR --exclude-device-files ,
.BR --exclude-filelist ,
.BR --exclude-filelist-stdin ,
.BR --exclude-regexp ,
.BR --include ,
.BR --include-filelist ,
.BR --include-filelist-stdin ,
and
.BR --include-regexp .
Each file selection condition either matches or doesn't match a given
file.  A given file is excluded by the file selection system exactly
when the first matching file selection condition specifies that the
file be excluded; otherwise the file is included.

For instance,
.PP
.RS
rdiff-backup --include /usr --exclude /usr /usr /backup
.PP
.RE
is exactly the same as
.PP
.RS
rdiff-backup /usr /backup
.PP
.RE
because the include and exclude directives match exactly the same
files, and the
.B --include
comes first, giving it precedence.  Similarly,
.PP
.RS
rdiff-backup --include /usr/local/bin --exclude /usr/local /usr /backup
.PP
.RE
would backup the /usr/local/bin directory (and its contents), but not
/usr/local/doc.

The
.B include
and
.B exclude
options accept
.IR "extended shell globbing patterns" .
These patterns can contain the special patterns
.BR * ,
.BR ** ,
.BR ? ,
and
.BR [...] .
As in a normal shell,
.B *
can be expanded to any string of characters not containing "/",
.B ?
expands to any character except "/", and
.B [...]
expands to a single character of those characters specified (ranges
are acceptable).  The new special pattern,
.BR ** ,
expands to any string of characters whether or not it contains "/".
Furthermore, if the pattern starts with "ignorecase:" (case
insensitive), then this prefix will be removed and any character in
the string can be replaced with an upper- or lowercase version of
itself.

Remember that you may need to quote these characters when typing them
into a shell, so the shell does not interpret the globbing patterns
before rdiff-backup sees them.

The
.BI "--exclude " pattern
option matches a file iff:
.TP
.B 1.
.I pattern
can be expanded into the file's filename, or
.TP
.B 2.
the file is inside a directory matched by the option.
.PP
.RE
Conversely,
.BI "--include " pattern
matches a file iff:
.TP
.B 1.
.I pattern
can be expanded into the file's filename,
.TP
.B 2.
the file is inside a directory matched by the option, or
.TP
.B 3.
the file is a directory which contains a file matched by the option.
.PP
.RE
For example,
.PP
.RS
.B --exclude
/usr/local
.PP
.RE
matches /usr/local, /usr/local/lib, and /usr/local/lib/netscape.  It
is the same as --exclude /usr/local --exclude '/usr/local/**'.
.PP
.RS
.B --include
/usr/local
.PP
.RE
specifies that /usr, /usr/local, /usr/local/lib, and
/usr/local/lib/netscape (but not /usr/doc) all be backed up.  Thus you
don't have to worry about including parent directories to make sure
that included subdirectories have somewhere to go.  Finally,
.PP
.RS
.B --include
ignorecase:'/usr/[a-z0-9]foo/*/**.py'
.PP
.RE
would match a file like /usR/5fOO/hello/there/world.py.  If it did
match anything, it would also match /usr.  If there is no existing
file that the given pattern can be expanded into, the option will not
match /usr.

The
.BR --include-filelist ,
.BR --exclude-filelist ,
.BR --include-filelist-stdin ,
and
.B --exclude-filelist-stdin
options also introduce file selection conditions.  They direct
rdiff-backup to read in a file, each line of which is a file
specification, and to include or exclude the matching files.  Lines
are separated by newlines or nulls, depending on whether the
--null-separator switch was given.  Each line in a filelist is
interpreted similarly to the way
.I extended shell patterns
are, with a few exceptions:
.TP
.B 1.
Globbing patterns like
.BR * ,
.BR ** ,
.BR ? ,
and
.B [...]
are not expanded.
.TP
.B 2.
Include patterns do not match files in a directory that is included.
So /usr/local in an include file will not match /usr/local/doc.
.TP
.B 3.
Lines starting with "+ " are interpreted as include directives, even
if found in a filelist referenced by
.BR --exclude-filelist .
Similarly, lines starting with "- " exclude files even if they are
found within an include filelist.

.RE
For example, if file "list.txt" contains the lines:

.RS
/usr/local
.RE
.RS
- /usr/local/doc
.RE
.RS
/usr/local/bin
.RE
.RS
+ /var
.RE
.RS
- /var

.RE
then "--include-filelist list.txt" would include /usr, /usr/local, and
/usr/local/bin.  It would exclude /usr/local/doc,
/usr/local/doc/python, etc.  It neither excludes nor includes
/usr/local/man, leaving the fate of this directory to the next
specification condition.  Finally, it is undefined what happens with
/var.  A single file list should not contain conflicting file
specifications.

Finally, the
.B --include-regexp
and
.B --exclude-regexp
allow files to be included and excluded if their filenames match a
python regular expression.  Regular expression syntax is too
complicated to explain here, but is covered in Python's library
reference.  Unlike the
.B --include
and
.B --exclude
options, the regular expression options don't match files containing
or contained in matched files.  So for instance
.PP
.RS
--include '[0-9]{7}(?!foo)'
.PP
.RE
matches any files whose full pathnames contain 7 consecutive digits
which aren't followed by 'foo'.  However, it wouldn't match /home even
if /home/ben/1234567 existed.

.SH BUGS
rdiff-backup uses the shell command
.BR mknod (1)
to backup device files (e.g. /dev/ttyS0), so device files won't be
handled correctly on systems with non-standard mknod syntax.
.PP
Files whose names are close to the maximum length (e.g. 235 chars if
the maximum is 255) may be skipped because the filenames of related
increment files would be too long.

.SH AUTHOR
Ben Escoto <bescoto@stanford.edu>
.PP
Feel free to ask me questions or send me bug reports, but also check
out the mailing list mentioned below.

.SH SEE ALSO
.BR python (1),
.BR rdiff (1),
.BR rsync (1),
.BR ssh (1).
The main rdiff-backup web page is at
.IR http://www.stanford.edu/~bescoto/rdiff-backup .
There also a mailing list described at
.IR http://keywest.Stanford.EDU/mailman/listinfo/rdiff-backup .