backy 2.0b1

Backup and restore for block devices.

Backy

This is work in progress. Parts of this file are currently fiction.

Backy is a block-based backup utility for virtual machines (i.e. volume files).

Backy is intended to be:

• space-, time-, and network-efficient

• trivial to restore

• reliable

To achieve this, we rely on:

• using a copy-on-write filesystem (like ZFS or btrfs) as the target filesystem to achieve space-efficiency

• using a snapshot-capable main storage for our volumes (e.g. Ceph, LVM, …) that allows easy extraction of changes between snapshots

• leverage proven, existing low-level tools

• keep the code-base small, simple, and well-tested.

Synopsis

backy –help

backy [-b <backupdir>] init

backy [-b <backupdir>] backup

backy [-b <backupdir>] status

Disaster recovery / full restore

The most important question is: I screwed up - how do I get my data back?

Here’s the fast answer to make a full restore of the most recent backup:

$ cd /srv/backy/my-virtual-machine
$ dd if=latest of=/srv/kvm/my-virtual-machine bs=4048000

If you like to pick a specific version, it’s only a little more effort:

$ cd /srv/backy/my-virtual-machine
$ backy status
== Revisions
2014-04-25 10:07:51 96d8b001-0ffc-4149-8c35-cf003f5638d6    20.00 GiB   252s
2014-04-25 10:13:20 d95e4f6c-cfef-48ee-aec2-d7c9e91c1bec    24.34 MiB   13s

== Summary
2 revisions
20.02 GiB data (estimated)
$ dd if=96d8b001-0ffc-4149-8c35-cf003f5638d6 of=/srv/kvm/my-virtual-machine bs=4048000

Restoring individual files

The image files are exact copies of the data from the virtual disks. You can use regular Linux tools to interact with them:

$ cd /srv/backy/my-virtual-machine
$ ls -lah latest
lrwxrwxrwx 1 root root  36 Apr 25 10:13 last -> d95e4f6c-cfef-48ee-aec2-d7c9e91c1bec
$ kpartx -av d95e4f6c-cfef-48ee-aec2-d7c9e91c1bec
add map loop0p1 (253:9): 0 41934815 linear /dev/loop0 8192
$ mkdir /root/restore
$ mount -o ro /dev/mapper/loop0p1 /root/restore
$ cd /root/restore
$ ls
bin  boot  dev  etc  home  lib  lost+found  media  mnt  opt  proc  root  run  sbin  srv  sys  tmp  usr  var

To clean up:

$ cd /srv/backy/my-virtual-machine
$ umount /root/restore
$ kpartx -av d95e4f6c-cfef-48ee-aec2-d7c9e91c1bec

Backup sub-command

Do a backup.

This includes checking whether a backup is needed, cleaning up from previous incomplete backups, and removing backups that are no longer needed according to the schedule.

If no backup is needed, just exit silently.

Status sub-command

Show backup inventory and provide summary information about backup health.

Revision specifications

If a command expects a single revision, you can specify full UUIDs, or numbers. Numbers specify the N-th newest revision (0 being the the newest, 1 the previous revision, and so on).

If multiple revisions may be given you can pass a single revision (as described above) or the word all to match all existing revisions.

Examples

(TBD)

Exit status

• 0: Command worked properly.

• 1: An error occured.

Authors

• Daniel Kraft <[e-mail]>

• Christian Theune <[e-mail]>

License

GPLv3

Hacking

Backy is intended to be compatible with Python 3.2 and 3.3. It is expected to work properly on Linux and Mac OS X, even though specific backends may not be avaible on some platforms:

$ hg clone https://bitbucket.org/ctheune/backy
$ cd backy
$ virtualenv --python=python3.3 .
$ bin/python bootstrap.py
$ bin/buildout
$ bin/py.test

Changelog

2.0b1 (2014-07-07)

• Clean up docs.

• Add classifiers in setup.py.

• More or less complete rewrite expecting a copy-on-write filesystem as the target.

• Flexible backup scheduling using free-form tags.

• Compatible with Python 3.2-3.4.

• Initial open source import as provided by Daniel Kraft (D9T).