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James Pharaoh

This is a partial Rust clone of ZBackup, along with some unique features of its own.

This project is free software and available under the [Apache 2.0 licence] (

Binaries for ubuntu are available can be downloaded [here] (

Online documentation is automatically generated by [] (

List of features

  • Rust library for access to ZBackup repositories
  • Supports encrypted and non encrypted formats
  • Multi-threaded restore and configurable, multi-tier chunk cache
  • Client/server utilities to efficiently restore multiple backups with a shared chunk cache
  • RandomAccess implements Read and Seek to provide efficient random access for rust applications
  • Balance tools to redistribute data in index and bundle files, typically useful to obtain a smaller number of consistently-sized files
  • Thorough garbage collection tools to clean up indexes and chunks which are no longer in use
  • Check tools, to verify the integrity of the repository in various ways, and repair simple problems
  • Command line decrypt utility, mostly useful for debugging

Notable missing features

  • No facility to create backups, these must be performed with the original ZBackup tool

Library usage

In cargo.toml:

output = "0.5"
rzbackup = "3.3"

A basic example (from examples/

extern crate output;
extern crate rzbackup;

use std::env;
use std::ffi::OsString;
use std::io;

use rzbackup::Repository;

fn main () {

	let output =
		output::open ();

	let arguments: Vec <OsString> =
		env::args_os ().collect ();

	let repository =
		Repository::open (
			& output,
			Repository::default_config (),
			& arguments [1],
			if arguments [2] != "" {
				Some (& arguments [2])
			} else { None },
		).unwrap ();

	let stdout =
		io::stdout ();

	let mut stdout_lock =
		stdout.lock ();

	repository.restore (
		& output,
		arguments [3],
		& mut stdout_lock,
	).unwrap ();


Command usage


The restore command is able to perform a one-off restore. It is basically equivalent to ZBackup's own restore command. The restored content is piped to stdout.

rzbackup restore \
	--repository REPOSITORY \
	[--password-file PASSWORD-FILE] \
	--backup-name BACKUP-NAME


The server process listens for client connections and streams backups over a socket. It has a large cache and so will be more efficient than running separate restore processes for backed up data with lots of shared deduplicated content.

rzbackup server \
	--listen-address HOST:PORT \
	--repository REPOSITORY \
	[--password-file PASSWORD-FILE] \
	... (lots more options, try --help)


The client connects to the server and streams a backup to standard output. It can also tell the server to reload its indexes, which will be necessary if new backups have been made.

rzbackup client reindex \
	--server-address HOST:PORT
rzbackup client restore \
	--server-address HOST:PORT \
	--backup-name BACKUP-NAME


The convert tool makes low-level changes to the repository. It is able to balance both index and bundle files, changing the number of entries they contain. It can perform garbage collection, removing index entries and chunk data which is no longer referenced by any backups. It is able to perform various consistency checks.

Balance bundles

rzbackup convert balance-bundles \
    --repository REPOSITORY \
    --password-file PASSWORD-FILE \
    [--chunks-per-bundle CHUNKS-PER-BUNDLE] \
    [--fill-factor FILL-FACTOR]

The balance-bundles tool balances the number of chunks contained in bundle files. This consists of reading all index files in order to determine which bundles contain more or less than the desired number of chunks, then reading those bundles and writing them out to new bundles with the required number of chunks in each one.

This writes out a new index file for each bundle, currently, so you may want to follow this by running balance-indexes.

The number of chunks per bundle is configurable on the command line, this currently defaults to 256, which is considerably higher than zbackup's own 32. The fill factor defaults to 25, this is a percentage of the chunks per bundle which will determine the minimum percentage of the total chunks which a bundle should have in order to be left as-is.

Balance indexes

rzbackup convert balance-indexes \
    --repository REPOSITORY \
    --password-file PASSWORD-FILE \
    [--bundles-per-index BUNDLES-PER-INDEX]

The balance-indexes tool balances the number of bundles indexed in individual index files. This consists of reading all indexes to determine which have more or less than the desired number of bundles, then writing out the information about those bundles to new index files with the desired number of bundles in each one.

The number of bundles per index is configurable on the command line, this currently defaults to 16384. ZBackup defaults to writing out a single index file every time a new backup is created (unless there are no bundles written), so index files vary in size and there are typically a large number of small indexes and a small number of large ones in a well-used repository.

Since, in general, every index file is loaded before doing any work on a repository, it makes sense to have fewer files, in order to reduce the overhead of opening a large number of files. This also makes synchronisation, eg to a remote location, more efficient.

Check backups

rzbackup convert check-backups \
    --repository REPOSITORY \
    --password-file PASSWORD-FILE \
    [--move-broken] \
    [--backup-name-hash-prefix] PREFIX

The check-backups command verifies all backups can be restored, by verifying that all the required chunks are present in the indexes. It can optionally move any backups which cannot be restored from backups to backups-broken, and it can operate on a subset of backups by specifying a prefix which is matched against the SHA1 sum of the backup name, eg /dir/filename for a backup in /backups/dir/filename.

It is a good idea to run rebuild-indexes before running this command, so that the state of the indexes is an accurate representation of the available chunks.

Check bundles

rzbackup convert check-bundles \
    --repository REPOSITORY \
    --password-file PASSWORD-FILE \
    [--bundle-name-prefix] PREFIX

The check-bundles tool simply reads every bundle in its entirety, applying consistency checks to the data they contain. This will verify the adler32 checksums after the bundle info at the start of the file and at the end of the file, and also checks that each chunk's data matches its truncated SHA1 sum which makes up the first 16 bytesof its chunk id. It also, implicitly, verifies that the compression and encryption are intact, since these are required to read the bundle.

Since this can take a very long time, a bundle name prefix can be specified, and only bundles whose names start with this string will be checked. This can be used, for example, to check a subset of bundles on a nightly basis.

This is useful to detect corruption in bundle files, which can then be restored from backups, if those are available. If backups are not available, then bundles can be removed, and these can be removed from the indexes using rebuild-indexes, preventing any future backups from being creating referencing these missing chunks.

Backups which are already broken can be identified by running check-backups after running rebuild-indexes. backups can be identified.

Check indexes

rzbackup convert check-indexes \
    --repository REPOSITORY \
    --password-file PASSWORD-FILE \

The check-indexes tool reads each backup file, building an index of all chunks which they reference, and then reads index files, reporting any missing or duplicated chunks. If the --repair option is specified, it will rewrite the index files to remove these chunks.

Garbage collect indexes

rzbackup convert gc-indexes \
    --repository REPOSITORY \
    --password-file PASSWORD-FILE

The gc-indexes tool performs garbage collection on index files. This consists of identifying all the chunks which are referenced by backups, then rewriting the index files to remove any chunks which are no longer needed.

Note that this will not make any changes to bundles, so you probably want to then run gc-bundles, to remove the chunks which are no longer needed.

Garbage collect bundles

rzbackup convert gc-bundles \
    --repository REPOSITORY \
    --password-file PASSWORD-FILE

The gc-bundles tool performs garbage collection on bundles. This consists of identifying all chunks which are referenced in index files, then rewriting the bundles to remove any chunks which are no longer needed.

This will also remove any chunks which are duplicated. These will not be removed from the index, which can cause problems with restore operations which reference the duplicated chunks, but this can be remedied with the rebuild-indexes tool.

Rebuild indexes

rzbackup convert rebuild-indexes \
    --repository REPOSITORY \
    --password-file PASSWORD-FILE

The rebuild-indexes tool scans all bundle files, reading only the chunk info in their header, then builds a completely new set of index files based on the information contained there. This is a useful way to ensure that the index files are correct, and can fix a lot of problems caused by various types of corruption.

This is important to ensure that restore operations can take place correctly when corruption has occurred, and also may be required for some of the other tools to work correctly, since they mostly rely on the index files only.


This is mostly useful for debugging. It allows you to show the decrypted contents of any backup, index or bundle file in a ZBackup repository.

rzbackup decrypt \
	--repository REPOSITORY \
	--password-file PASSWORD-FILE \
	--encrypted file ENCRYPTED-FILE