duplicity - Encrypted backup using rsync algorithm

duplicity [options] input_directory destination_url

duplicity [options] source_url target_directory

duplicity [options] --verify source_url filename

duplicity [options] --list-current-files source_url

duplicity [options] --cleanup target_url

Duplicity incrementally backs up files and directory by encrypting tar-format volumes with GnuPG and uploading them to a remote (or local) file server. In theory many remote backends are possible; right now local, ftp, ssh/scp, and rsync backends are available. Because duplicity uses librsync, the incremental archives are space efficient and only record the parts of files that have changed since the last backup. Currently duplicity supports deleted files, full unix permissions, directories, symbolic links, fifos, etc., but not hard links.

Duplicity will read the PASSPHRASE environment variable to find the passphrase to give to GnuPG. If this is not set, the user will be prompted for the passphrase.

If you are backing up the root directory /, remember to --exclude /proc, or else duplicity will probably crash on the weird stuff in there.

Here is an example of a backup, using scp to back up /home/me to some_dir on the other.host machine:

duplicity /home/me scp://uid@other.host/some_dir

If the above is run repeatedly, the first will be a full backup, and subsequent ones will be incremental. To force a full backup, use the --full option:

duplicity --full /home/me scp://uid@other.host/some_dir

Now suppose we accidentally delete /home/me and want to restore it the way it was at the time of last backup:

duplicity scp://uid@other.host/some_dir /home/me

Duplicity enters restore mode because the URL comes before the local directory. If we wanted to restore just the file "Mail/article" in /home/me as it was three days ago into /home/me/restored_file:

duplicity -t 3D --file-to-restore Mail/article scp://uid@other.host/some_dir /home/me/restored_file

The following command compares the files we backed up, so see what has changed since then:

duplicity --verify scp://uid@other.host/some_dir /home/me

Finally, duplicity recognizes several include/exclude options. For instance, the following will backup the root directory, but exclude /mnt, /tmp, and /proc:

duplicity --exclude /mnt --exclude /tmp --exclude /proc / file:///usr/local/backup

Note that in this case the destination is the local directory /usr/local/backup. The following will backup only the /home and /etc directories under root:

duplicity --include /home --include /etc --exclude '**' / file:///usr/local/backup

Duplicity can also access a repository via ftp. If a user name is given, the environment variable FTP_PASSWORD is read to determine the password:

FTP_PASSWORD=mypassword duplicity /local/dir ftp://user@other.host/some_dir

--allow-source-mismatch

Do not abort on attempts to use the same archive dir or remote backend to back up different directories. duplicity will tell you if you need this switch.

--archive-dir path

When restoring, specify the local archive directory. This option is not necessary, but if hash data is found locally in path it will be checked against remote files.

--cleanup

Delete the extraneous duplicity files on the given backend. Non-duplicity files, or files in complete data sets will not be deleted. This should only be necessary after a duplicity session fails or is aborted prematurely.

--encrypt-key key

When backing up, encrypt to the given public key, instead of using symmetric (traditional) encryption. Can be specified multiple times.

--exclude shell_pattern

Exclude the file or files matched by shell_pattern. If a directory is matched, then files under that directory will also be matched. See the FILE SELECTION section for more information.

--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.

--exclude-filelist filename

Excludes the files listed in filename See the FILE SELECTION section for more information.

--exclude-filelist-stdin

Like --exclude-filelist, but the list of files will be read from standard input. See the FILE SELECTION section for more information.

--exclude-globbing-filelist filename

Like --exclude-filelist but each line of the filelist will be interpreted according to the same rules as --include and --exclude.

--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.

--exclude-regexp regexp

Exclude files matching the given regexp. Unlike the --exclude option, this option does not match files in a directory it matches. See the FILE SELECTION section for more information.

--file-to-restore path

This option may be given in restore mode, causing only path to be restored instead of the entire contents of the backup archive. path should be given relative to the root of the directory backed up.

-f, --full

Indicate full backup. If this is set, perform full backup even if signatures are available.

--force

Proceed even if data loss might result. Duplicity will let the user know when this option is required.

-i, --incremental

If this is set, duplicity will abort if old signatures cannot be found. The default is to switch to full backup under these conditions.

--include shell_pattern

Similar to --exclude but include matched files instead. Unlike --exclude, this option will also match parent directories of matched files (although not necessarily their contents). See the FILE SELECTION section for more information.

--include-filelist filename

Like --exclude-filelist, but include the listed files instead. See the FILE SELECTION section for more information.

--include-filelist-stdin

Like --include-filelist, but read the list of included files from standard input.

--include-globbing-filelist filename

Like --include-filelist but each line of the filelist will be interpreted according to the same rules as --include and --exclude.

--include-regexp regexp

Include files matching the regular expression regexp. Only files explicitly matched by regexp will be included by this option. See the FILE SELECTION section for more information.

--list-current-files

Lists the files currently backed up in the archive. The information will be extracted from the signature files, not the archive data itself. Thus the whole archive does not have to be downloaded, but on the other hand if the archive has been deleted or corrupted, this command may not detect it.

--no-encryption

Do not use GnuPG to encrypt files on remote system. Instead just write gzipped volumes.

--no-print-statistics

By default duplicity will print statistics about the current session after a successful backup. This switch disables that behavior.

--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.

--scp-command command

This option only matters when using the ssh/scp backend. There command will be used instead of scp to send or receive files. command must have the same syntax as scp. This option can also be used to give extra arguments to scp, for instance "--scp-command 'scp -i foo'". The default is "scp".

--sign-key key

This option can be used when backing up or restoring. When backing up, all backup files will be signed with keyid key. When restoring, duplicity will signal an error if any remote file is not signed with the given keyid. key should be an 8 character hex string, like AA0E73D2.

--ssh-command command

Use command instead of "ssh" to execute commands on the remote side. This only matters when using the ssh/scp backend. See --scp-command for more information.

--remove-older-than time

Delete all backup sets older than the given time. If old backup sets will not be deleted if backup sets newer than time depend on them. See the TIME FORMATS section for more information.

--short-filenames

If this option is specified, the names of the files duplicity writes will be shorter (about 30 chars) but less understandable. This may be useful when backing up to MacOS or another OS or FS that doesn't support long filenames.

-ttime, --restore-time time

When restoring, specify the time to restore to.

-v[0-9], --verbosity [0-9]

Specify verbosity level (0 is total silent, 3 is the default, and 9 is noisiest).

--verify

Enter verify mode instead of restore. If the --file-to-restore option is given, restrict verify to that file or directory. duplicity will exit with a non-zero error level if any files are different. On verbosity level 4 or higher, log a message for each file that has changed.

duplicity uses time strings in two places. Firstly, many of the files duplicity 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.

Secondly, the -t, and --restore-time options take a time string, which can be given in any of several formats:

1.

the string "now" (refers to the current time)

2.

a sequences of digits, like "123456890" (indicating the time in seconds after the epoch)

3.

A string like "2002-01-25T07:00:00+02:00" in datetime format

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.

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.

duplicity accepts the same file selection options rdiff-backup does, including --exclude, --exclude-filelist-stdin, etc.

When duplicity 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: --exclude, --exclude-device-files, --exclude-filelist, --exclude-filelist-stdin, --exclude-globbing-filelist, --exclude-regexp, --include, --include-filelist, --include-filelist-stdin, --include-globbing-filelist, and --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,

duplicity --include /usr --exclude /usr /usr scp://user@host/backup

is exactly the same as

duplicity /usr scp://user@host/backup

because the include and exclude directives match exactly the same files, and the --include comes first, giving it precedence. Similarly,

duplicity --include /usr/local/bin --exclude /usr/local /usr scp://user@host/backup

would backup the /usr/local/bin directory (and its contents), but not /usr/local/doc.

The include, exclude, include-globbing-filelist, and exclude-globbing-filelist options accept extended shell globbing patterns. These patterns can contain the special patterns *, **, ?, and [...]. As in a normal shell, * can be expanded to any string of characters not containing "/", ? expands to any character except "/", and [...] expands to a single character of those characters specified (ranges are acceptable). The new special pattern, **, 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 duplicity sees them.

The --exclude pattern option matches a file iff:

1.

pattern can be expanded into the file's filename, or

2.

the file is inside a directory matched by the option.

Conversely, --include pattern matches a file iff:

1.

pattern can be expanded into the file's filename,

2.

the file is inside a directory matched by the option, or

3.

the file is a directory which contains a file matched by the option.

For example,

--exclude /usr/local

matches /usr/local, /usr/local/lib, and /usr/local/lib/netscape. It is the same as --exclude /usr/local --exclude '/usr/local/**'.

--include /usr/local

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,

--include ignorecase:'/usr/[a-z0-9]foo/*/**.py'

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 --include-filelist, --exclude-filelist, --include-filelist-stdin, and --exclude-filelist-stdin options also introduce file selection conditions. They direct duplicity 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 extended shell patterns are, with a few exceptions:

1.

Globbing patterns like *, **, ?, and [...] are not expanded.

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.

3.

Lines starting with "+ " are interpreted as include directives, even if found in a filelist referenced by --exclude-filelist. Similarly, lines starting with "- " exclude files even if they are found within an include filelist.

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

/usr/local - /usr/local/doc /usr/local/bin + /var - /var

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.

The --include-globbing-filelist and --exclude-globbing-filelist options also specify filelists, but each line in the filelist will be interpreted as a globbing pattern the way --include and --exclude options are interpreted (although "+ " and "- " prefixing is still allowed). For instance, if the file "globbing-list.txt" contains the lines:

dir/foo + dir/bar - **

Then "--include-globbing-filelist globbing-list.txt" would be exactly the same as specifying "--include dir/foo --include dir/bar --exclude **" on the command line.

Finally, the --include-regexp and --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 --include and --exclude options, the regular expression options don't match files containing or contained in matched files. So for instance

--include '[0-9]{7}(?!foo)'

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.

This section describes duplicity's basic operation and the format of its data files. It should not necessary to read this section to use duplicity.

The files used by duplicity to store backup data are tarfiles in GNU tar format. They can be produced independently by rdiffdir(1). For incremental backups, new files are saved normally in the tarfile. But when a file changes, instead of storing a complete copy of the file, only a diff is stored, as generated by rdiff(1). If a file is deleted, a 0 length file is stored in the tar. It is possible to restore a duplicity archive "manually" by using tar and then cp, rdiff, and rm as necessary. These duplicity archives have the extension difftar.

Both full and incremental backup sets have the same format. In effect, a full backup set is an incremental one generated from an empty signature (see below). The files in full backup sets will start with duplicity-full while the incremental sets start with duplicity-inc. When restoring, duplicity applies patches in order, so deleting, for instance, a full backup set may make related incremental backup sets unuseable.

In order to determine which files have been deleted, and to calculate diffs for changed files, duplicity needs to process information about previous sessions. It stores this information in the form of tarfiles where each entry's data contains the signature (as produced by rdiff) of the file instead of the file's contents. These signature sets have the extension sigtar.

Signature files are not required to restore a backup set, but without an up-to-date signature, duplicity cannot append an incremental backup to an existing archive.

To save bandwidth, duplicity generates full signature sets and incremental signature sets. A full signature set is generated for each full backup, and an incremental one for each incremental backup. These start with duplicity-full-signatures and duplicity-new-signatures respectively. If --archive-dir is used, these signatures will be stored locally only, which further saves bandwidth.

Hard links currently unsupported (they will be treated as non-linked regular files).

Bad signatures will be treated as empty instead of logging appropriate error message.

Ben Escoto <bescoto@stanford.edu>

rdiffdir(1), python(1), rdiff(1), rdiff-backup(1).