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byteback - maintenance-free client & server backup scripts for Linux
====================================================================
byteback encapsulates Bytemark's "best practice" for maintenance-free backups
with easy client and server setup.
"Maintenance-free" means that we'd rather make full use of a fixed amount of
disc space. Management of disc space must be completely automatic, so the
process never grinds to a halt for reasons that could be automatically
resolved. Failed backups can be restarted in case of network problems.
We use the standard OpenSSH on the server for encrypted transport & access
control, btrfs for simple snapshots and rsync for efficient data transfer
across the network.
Backups should require as little configuration as possible to be safe - just
the server address should be enough.
Setting up: server
------------------
Install the 'byteback' package on the server, along with its dependencies
(rsync and ruby-ffi).
You then need to perform the following local setup on the server, which can
securely handle backups for multiple clients. You need a dedicated user
(which is usually called 'byteback') with a home directory on a btrfs
filesystem. You will need to mount the filesystem with the
'user_subvol_rm_allowed' flag to enable pruning to work (or run that part
as root).
The following commands are appropriate for a Debian system, you might need
to alter it for other Linux distributions, or if you are not using LVM
for your discs:
# Create a dedicated UNIX user which will store everyone's backups, and
# allow logins
#
adduser --system byteback --home /byteback --shell /bin/bash
# Create a dedicated btrfs filesystem for the user, and add that as its home
#
lvcreate my_volume_group --name byteback --size 1000GB
mkfs.btrfs /dev/my_volume_group/byteback
echo '/dev/my_volume_group/byteback /byteback btrfs noatime,space_cache,compress=lzo,clear_cache,autodefrag,user_subvol_rm_allowed 0 0' >>/etc/fstab
mount /byteback
chown byteback /byteback
chmod u+w /byteback
Finally, before setting up the client, add
PermitUserEnvironment yes
to /etc/ssh/sshd_config, and restart sshd.
Setting up: client
------------------
Clients are machines that need to be backed up. Assuming you can log into
the remote 'byteback' user with a password or administrative key, you only
need to type one command on the client to set things going:
sudo byteback-setup-client --destination byteback@mybackuphost.net:
If this goes OK, you are ready to start backing up. I'd advise taking the
first backup manually to make sure it goes as you expect. Type this on the
client to start and watch the backup.
sudo byteback-backup --verbose
Configuring byteback-backup
---------------------------
This is now documented in the manapge for byteback-backup(1).
Viewing and restoring backups
-----------------------------
This is now documented in the manapge for byteback-restore(1).
The trust model
---------------
Backups are intended to keep your data safe, and byteback makes the assumption
that the client may become hostile to the backup server. At Bytemark this
allows us to guard against rogue employees of our clients destroying the backup,
while ensuring that our clients can still access all their old backups. There
are several measures to guard against this, though they are all ineffective
over a long enough period of time:
* the server uses SSH's command feature to ensure that clients can only
run rsync to the appropriate directory;
* the server's snapshots are read-only, so the client can't just rsync an
empty directory over an old backup;
* the server will refuse to take snapshots "too often" to stop the client
from filling the disc with useless data;
* the server will refuse to prune away space for a new backup that is
suddenly larger than previous ones.
Pruning behaviour
-----------------
This is now documented in byteback-prune(1).
Acknowledgements
----------------
For maximum portability, I've included three libraries. Thanks very much to
their authors:
* sys-filesystem by Daniel J. Berger: https://github.com/djberg96/sys-filesystem
* trollop by William Morgan: https://github.com/wjessop/trollop
* ffi-xattr by Jari Bakken: https://github.com/jarib/ffi-xattr
|
