.. image:: https://travis-ci.org/ccomb/buttervolume.svg?branch=master :target: https://travis-ci.org/ccomb/buttervolume :alt: Travis state
What will Buttervolume allow you to do?
What can Buttervolume do?
How does it work?
Buttervolume is a Docker Volume Plugin that stores each Docker volume as a BTRFS subvolume.
.. contents::
Introduction
BTRFS <https://btrfs.wiki.kernel.org/>_ is a next-generation copy-on-write
filesystem with subvolume and snapshot support. A BTRFS subvolume <https://btrfs.wiki.kernel.org/index.php/SysadminGuide#Subvolumes>_ can be
seen as an independant file namespace that can live in a directory and can be
mounted as a filesystem and snapshotted individually.
On the other hand, Docker volumes <https://docs.docker.com/storage/volumes/>_ are commonly used
to store persistent data of stateful containers, such as a MySQL/PostgreSQL
database or an upload directory of a CMS. By default, Docker volumes are just
local directories in the host filesystem. A number of Volume plugins <https://docs.docker.com/engine/extend/legacy_plugins/#/volume-plugins>_
already exist for various storage backends, including distributed filesystems,
but small clusters often can't afford to deploy a distributed filesystem.
We believe BTRFS subvolumes are a powerful and lightweight storage solution for Docker volumes, allowing fast and easy replication (and backup) across several nodes of a small cluster.
Prerequisites
Make sure the directory /var/lib/buttervolume/ is living in a BTRFS
filesystem. It can be a BTRFS mountpoint or a BTRFS subvolume or both.
You should also create the directories for the config and ssh on the host::
sudo mkdir /var/lib/buttervolume
sudo mkdir /var/lib/buttervolume/config
sudo mkdir /var/lib/buttervolume/ssh
Build and run as a contributor
If you want to be a contributor, read this chapter. Otherwise jump to the next section.
You first need to create a root filesystem for the plugin, using the provided Dockerfile::
git clone https://github.com/ccomb/buttervolume
./build.sh
By default the plugin is built for the latest commit (HEAD). You can build another version by specifying it like this::
./build.sh 3.7
At this point, you can set the SSH_PORT option for the plugin by running::
docker plugin set ccomb/buttervolume SSH_PORT=1122
Note that this option is only relevant if you use the replication feature between two nodes.
Now you can enable the plugin, which should start buttervolume in the plugin container::
docker plugin enable ccomb/buttervolume:HEAD
You can check it is responding by running a buttervolume command::
export RUNCROOT=/run/docker/runtime-runc/plugins.moby/ # or /run/docker/plugins/runtime-root/plugins.moby/
alias drunc="sudo runc --root $RUNCROOT"
alias buttervolume="drunc exec -t $(drunc list|tail -n+2|awk '{print $1}') buttervolume"
sudo buttervolume scheduled
Increase the log level by writing a /var/lib/buttervolume/config/config.ini file with::
[DEFAULT]
TIMER = 120
Then check the logs with::
sudo journalctl -f -u docker.service
You can also locally install and run the plugin in the foreground with::
python3 -m venv venv
./venv/bin/python setup.py develop
sudo ./venv/bin/buttervolume run
Then you can use the buttervolume CLI that was installed in developer mode in the venv::
./venv/bin/buttervolume --version
Install and run as a user
If the plugin is already pushed to the image repository, you can install it with::
docker plugin install ccomb/buttervolume
Check it is running::
docker plugin ls
Find your runc root, then define useful aliases::
export RUNCROOT=/run/docker/runtime-runc/plugins.moby/ # or /run/docker/plugins/runtime-root/plugins.moby/
alias drunc="sudo runc --root $RUNCROOT"
alias buttervolume="drunc exec -t $(drunc list|tail -n+2|awk '{print $1}') buttervolume"
And try a buttervolume command::
buttervolume scheduled
Or create a volume with the driver. Note that the name of the driver is the name of the plugin::
docker volume create -d ccomb/buttervolume:latest myvolume
Note that instead of using aliases, you can also define functions that you can put in your .bash_profile or .bash_aliases::
function drunc () {
RUNCROOT=/run/docker/runtime-runc/plugins.moby/ # or /run/docker/plugins/runtime-root/plugins.moby/
sudo runc --root $RUNCROOT $@
}
function buttervolume () {
drunc exec -t $(docker plugin ls --no-trunc | grep 'ccomb/buttervolume:latest' | awk '{print $1}') buttervolume $@
}
Upgrade
You must force disable it before reinstalling it (as explained in the docker documentation)::
docker plugin disable -f ccomb/buttervolume
docker plugin rm -f ccomb/buttervolume
docker plugin install ccomb/buttervolume
Configure
You can configure the following variables:
* ``DRIVERNAME``: the full name of the driver (with the tag)
* ``VOLUMES_PATH``: the path where the BTRFS volumes are located
* ``SNAPSHOTS_PATH``: the path where the BTRFS snapshots are located
* ``TEST_REMOTE_PATH``: the path during unit tests where the remote BTRFS snapshots are located
* ``SCHEDULE``: the path of the scheduler configuration
* ``RUNPATH``: the path of the docker run directory (/run/docker)
* ``SOCKET``: the path of the unix socket where buttervolume listens
* ``TIMER``: the number of seconds between two runs of the scheduler jobs
* ``DTFORMAT``: the format of the datetime in the logs
* ``LOGLEVEL``: the Python log level (INFO, DEBUG, etc.)
The configuration can be done in this order of priority:
#. from an environment variable prefixed with ``BUTTERVOLUME_`` (ex: ``BUTTERVOLUME_TIMER=120``)
#. from the [DEFAULT] section of the ``/etc/buttervolume/config.ini`` file
inside the container or ``/var/lib/buttervolume/config/config.ini`` on the
host
Example of config.ini file::
[DEFAULT]
TIMER = 120
If none of this is configured, the following default values are used:
* ``DRIVERNAME = ccomb/buttervolume:latest``
* ``VOLUMES_PATH = /var/lib/buttervolume/volumes/``
* ``SNAPSHOTS_PATH = /var/lib/buttervolume/snapshots/``
* ``TEST_REMOTE_PATH = /var/lib/buttervolume/received/``
* ``SCHEDULE = /etc/buttervolume/schedule.csv``
* ``RUNPATH = /run/docker``
* ``SOCKET = $RUNPATH/plugins/btrfs.sock`` # only if run manually
* ``TIMER = 60``
* ``DTFORMAT = %Y-%m-%dT%H:%M:%S.%f``
* ``LOGLEVEL = INFO``
Usage
The normal way to run it is as a new-style Docker Plugin as described above in
the "Install and run" section, which will start it automatically. This will
create a /run/docker/plugins/<uuid>/btrfs.sock file to be used by the
Docker daemon. The <uuid> is the unique identifier of the runc/OCI
container running it. This means you can probably run several versions of the
plugin simultaneously but this is currently not recommended unless you keep in
mind the volumes and snapshots are in the same place for the different
versions. Otherwise you can configure a different path for the volumes and
snapshots of each different versions using the config.ini file.
Then the name of the volume driver is the name of the plugin::
docker volume create -d ccomb/buttervolume:latest myvolume
or::
docker volume create --volume-driver=ccomb/buttervolume:latest
When creating a volume, you can choose to disable copy-on-write on a per-volume
basis. Just use the -o or --opt option as defined in the Docker documentation <https://docs.docker.com/engine/reference/commandline/volume_create/#options>_ ::
docker volume create -d ccomb/buttervolume -o copyonwrite=false myvolume
If you installed it locally as a Python distribution, you can also start it manually with::
sudo buttervolume run
In this case it will create a unix socket in /run/docker/plugins/btrfs.sock
for use by Docker with the legacy plugin system. Then the name of the volume
driver is the name of the socket file::
docker volume create -d btrfs myvolume
or::
docker create --volume-driver=btrfs
When started, the plugin will also start its own scheduler to run periodic jobs (such as a snapshot, replication, purge or synchronization)
Once the plugin is running, whenever you create a container you can specify the
volume driver with docker create --volume-driver=ccomb/buttervolume --name <name> <image>. You can also manually create a BTRFS volume with docker volume create -d ccomb/buttervolume. It also works with docker-compose, by specifying the
ccomb/buttervolume driver in the volumes section of the compose file.
When you delete the volume with docker rm -v <container> or docker volume rm <volume>, the BTRFS subvolume is deleted. If you snapshotted the volume
elsewhere in the meantime, the snapshots won't be deleted.
When buttervolume is installed, it provides a command line tool
buttervolume, with the following subcommands::
run Run the plugin in foreground
snapshot Snapshot a volume
snapshots List snapshots
schedule Schedule, unschedule, pause or resume a periodic snapshot, replication, synchronization or purge
scheduled List, pause or resume all the scheduled actions
restore Restore a snapshot (optionally to a different volume)
clone Clone a volume as new volume
send Send a snapshot to another host
sync Synchronise a volume from a remote host volume
rm Delete a snapshot
purge Purge old snapshot using a purge pattern
You can create a readonly snapshot of the volume with::
buttervolume snapshot <volume>
The volumes are currently expected to live in /var/lib/buttervolume/volumes and
the snapshot will be created in /var/lib/buttervolume/snapshots, by appending the
datetime to the name of the volume, separated with @.
You can list all the snapshots::
buttervolume snapshots
or just the snapshots corresponding to a volume with::
buttervolume snapshots <volume>
<volume> is the name of the volume, not the full path. It is expected
to live in /var/lib/buttervolume/volumes.
You can restore a snapshot as a volume. The current volume will first be snapshotted, deleted, then replaced with the snapshot. If you provide a volume name instead of a snapshot, the latest snapshot is restored. So no data is lost if you do something wrong. Please take care of stopping the container before restoring a snapshot::
buttervolume restore <snapshot>
<snapshot> is the name of the snapshot, not the full path. It is expected
to live in /var/lib/buttervolume/snapshots.
By default, the volume name corresponds to the volume the snapshot was created from. But you can optionally restore the snapshot to a different volume name by adding the target as the second argument::
buttervolume restore <snapshot> <volume>
You can clone a volume as a new volume. The current volume will be cloned as a new volume name given as parameter. Please take care of stopping the container before cloning a volume::
buttervolume clone <volume> <new_volume>
<volume> is the name of the volume to be cloned, not the full path. It is expected
to live in /var/lib/buttervolume/volumes.
<new_volume> is the name of the new volume to be created as clone of previous one,
not the full path. It is expected to be created in /var/lib/buttervolume/volumes.
You can delete a snapshot with::
buttervolume rm <snapshot>
<snapshot> is the name of the snapshot, not the full path. It is expected
to live in /var/lib/buttervolume/snapshots.
You can incrementally send snapshots to another host, so that data is replicated to several machines, allowing to quickly move a stateful docker container to another host. The first snapshot is first sent as a whole, then the next snapshots are used to only send the difference between the current one and the previous one. This allows to replicate snapshots very often without consuming a lot of bandwith or disk space::
buttervolume send <host> <snapshot>
<snapshot> is the name of the snapshot, not the full path. It is expected
to live in /var/lib/buttervolume/snapshots and is replicated to the same path on
the remote host.
<host> is the hostname or IP address of the remote host. The snapshot is
currently sent using BTRFS send/receive through ssh, with an ssh server direcly
included in the plugin. This requires that ssh keys be present and already
authorized on the target host (under /var/lib/buttervolume/ssh), and that
the StrictHostKeyChecking no option be enabled in
/var/lib/buttervolume/ssh/config on local host.
Please note you have to restart you docker daemons each time you change ssh configuration.
The default SSH_PORT of the ssh server included in the plugin is 1122. You can
change it with docker plugin set ccomb/buttervolume SSH_PORT=<PORT> before
enabling the plugin.
You can receive data from a remote volume, so in case there is a volume on
the remote host with the same name, it will get new and most recent data
from the distant volume and replace in the local volume. Before running the
rsync command a snapshot is made on the local machine to manage recovery::
buttervolume sync <volume> <host1> [<host2>][...]
The intent is to synchronize a volume between multi hosts on running containers, so you should schedule that action on each nodes from all remote hosts.
.. note::
As we are pulling data from multiple hosts we never remove data, consider removing scheduled actions before removing data on each hosts.
.. warning::
Make sure your application is able to handle such synchronisation
You can purge old snapshot corresponding to the specified volume, using a retention pattern::
buttervolume purge <pattern> <volume>
If you're unsure whether you retention pattern is correct, you can run the
purge with the --dryrun option, to inspect what snapshots would be deleted,
without deleting them::
buttervolume purge --dryrun <pattern> <volume>
<volume> is the name of the volume, not the full path. It is expected
to live in /var/lib/buttervolume/volumes.
<pattern> is the snapshot retention pattern. It is a semicolon-separated
list of time length specifiers with a unit. Units can be m for minutes,
h for hours, d for days, w for weeks, y for years. The pattern
should have at least 2 items.
Here are a few examples of retention patterns:
4h:1d:2w:2y
Keep all snapshots in the last four hours, then keep only one snapshot
every four hours during the first day, then one snapshot per day during
the first two weeks, then one snapshot every two weeks during the first
two years, then delete everything after two years.
4h:1w
keep all snapshots during the last four hours, then one snapshot every
four hours during the first week, then delete older snapshots.
2h:2h
keep all snapshots during the last two hours, then delete older snapshots.
You can schedule, pause or resume a periodic job, such as a snapshot, a
replication, a synchronization or a purge. The schedule it self is stored in
/etc/buttervolume/schedule.csv.
Schedule a snapshot of a volume every 60 minutes::
buttervolume schedule snapshot 60 <volume>
Pause this schedule::
buttervolume schedule snapshot pause
Resume this schedule::
buttervolume schedule snapshot resume
Remove this schedule by specifying a timer of 0 min (or delete)::
buttervolume schedule snapshot 0 <volume>
Schedule a replication of volume foovolume to remote_host::
buttervolume schedule replicate:remote_host 3600 foovolume
Remove the same schedule::
buttervolume schedule replicate:remote_host 0 foovolume
Schedule a purge every hour of the snapshots of volume foovolume, but
keep all the snapshots in the last 4 hours, then only one snapshot every 4
hours during the first week, then one snapshot every week during one year, then
delete all snapshots after one year::
buttervolume schedule purge:4h:1w:1y 60 foovolume
Remove the same schedule::
buttervolume schedule purge:4h:1w:1y 0 foovolume
Using the right combination of snapshot schedule timer, purge schedule timer and purge retention pattern, you can create you own backup strategy, from the simplest ones to more elaborate ones. A common one is the following::
buttervolume schedule snapshot 1440 <volume>
buttervolume schedule purge:1d:4w:1y 1440 <volume>
It should create a snapshot every day, then purge snapshots everydays while keeping all snapshots in the last 24h, then one snapshot per day during one month, then one snapshot per month during only one year.
Schedule a syncrhonization of volume foovolume from remote_host1
abd remote_host2::
buttervolume schedule synchronize:remote_host1,remote_host2 60 foovolume
Remove the same schedule::
buttervolume schedule synchronize:remote_host1,remote_host2 0 foovolume
You can list all the scheduled job with::
buttervolume scheduled
or::
buttervolume scheduled list
It will display the schedule in the same format used for adding the schedule, which is convenient to remove an existing schedule or add a similar one.
Pause all the scheduled jobs::
buttervolume scheduled pause
Resume all the scheduled jobs::
buttervolume scheduled resume
The global job pause/resume feature is implemented separately from the individual job pause/resume. So it will not affect your individual pause/resume settings.
Copy-On-Write is enabled by default. You can disable it if you really want.
Why disabling copy-on-write? If your docker volume stores databases such as PostgreSQL or MariaDB, the copy-on-write feature may hurt performance, though the latest kernels have improved a lot. The good news is that disabling copy-on-write does not prevent from doing snaphots.
Testing
If your volumes directory is a BTRFS partition or volume, tests can be run with::
./test.sh
Working without a BTRFS partition
If you have no BTRFS partitions or volumes you can setup a virtual partition in a file as follows (tested on Debian 8):
Setup BTRFS virtual partition::
sudo qemu-img create /var/lib/docker/btrfs.img 10G
sudo mkfs.btrfs /var/lib/docker/btrfs.img
.. note::
you can ignore the error, in fact the new FS is formatted
Mount the partition somewhere temporarily to create 3 new BTRFS subvolumes::
sudo -s
mkdir /tmp/btrfs_mount_point
mount -o loop /var/lib/docker/btrfs.img /tmp/btrfs_mount_point/
btrfs subvolume create /tmp/btrfs_mount_point/snapshots
btrfs subvolume create /tmp/btrfs_mount_point/volumes
btrfs subvolume create /tmp/btrfs_mount_point/received
umount /tmp/btrfs_mount_point/
rm -r /tmp/btrfs_mount_point/
Stop docker, create required mount point and restart docker::
systemctl stop docker
mkdir -p /var/lib/buttervolume/volumes
mkdir -p /var/lib/buttervolume/snapshots
mkdir -p /var/lib/buttervolume/received
mount -o loop,subvol=volumes /var/lib/docker/btrfs.img /var/lib/buttervolume/volumes
mount -o loop,subvol=snapshots /var/lib/docker/btrfs.img /var/lib/buttervolume/snapshots
mount -o loop,subvol=received /var/lib/docker/btrfs.img /var/lib/buttervolume/received
systemctl start docker
Once you are done with your test, you can unmount those volumes and you will find back your previous docker volumes::
systemctl stop docker
umount /var/lib/buttervolume/volumes
umount /var/lib/buttervolume/snapshots
umount /var/lib/buttervolume/received
systemctl start docker
rm /var/lib/docker/btrfs.img
Migrate to version 3
If you're currently using Buttervolume 1.x or 2.0 in production, you must carefully follow the guidelines below to migrate to version 3.
First copy the ssh and config files and disable the scheduler::
sudo -s
docker cp buttervolume_plugin_1:/etc/buttervolume /var/lib/buttervolume/config
docker cp buttervolume_plugin_1:/root/.ssh /var/lib/buttervolume/ssh
mv /var/lib/buttervolume/config/schedule.csv /var/lib/buttervolume/config/schedule.csv.disabled
Then stop all your containers, excepted buttervolume
Now snapshot and delete all your volumes::
volumes=$(docker volume ls -f driver=ccomb/buttervolume:latest --format "{{.Name}}")
# or: # volumes=$(docker volume ls -f driver=ccomb/buttervolume:latest|tail -n+2|awk '{print $2}')
echo $volumes
for v in $volumes; do docker exec buttervolume_plugin_1 buttervolume snapshot $v; done
for v in $volumes; do docker volume rm $v; done
Then stop the buttervolume container, remove the old btrfs.sock file, and restart docker::
docker stop buttervolume_plugin_1
docker rm -v buttervolume_plugin_1
rm /run/docker/plugins/btrfs.sock
systemctl stop docker
If you were using Buttervolume 1.x, you must move your snapshots to the new location::
mkdir /var/lib/buttervolume/snapshots
cd /var/lib/docker/snapshots
for i in *; do btrfs subvolume snapshot -r $i /var/lib/buttervolume/snapshots/$i; done
Restore /var/lib/docker/volumes as the original folder::
cd /var/lib/docker
mkdir volumes.new
mv volumes/* volumes.new/
umount volumes # if this was a mounted btrfs subvolume
mv volumes.new/* volumes/
rmdir volumes.new
systemctl start docker
Change your volume configurations (in your compose files) to use the new
ccomb/buttervolume:latest driver name instead of btrfs
Then start the new buttervolume 3.x as a managed plugin and check it is started::
docker plugin install ccomb/buttervolume:latest
docker plugin ls
Then recreate all your volumes with the new driver and restore them from the snapshots::
for v in $volumes; do docker volume create -d ccomb/buttervolume:latest $v; done
export RUNCROOT=/run/docker/runtime-runc/plugins.moby/ # or /run/docker/plugins/runtime-root/plugins.moby/
alias drunc="sudo runc --root $RUNCROOT"
alias buttervolume="drunc exec -t $(drunc list|tail -n+2|awk '{print $1}') buttervolume"
# WARNING : check the the volume you will restore are the correct ones
for v in $volumes; do buttervolume restore $v; done
Then restart your containers, check they are ok with the correct data.
Reenable the schedule::
mv /var/lib/buttervolume/config/schedule.csv.disabled /var/lib/buttervolume/config/schedule.csv
Credits
Thanks to:
3.12 (2024-11-05)
3.11 (2024-10-12)
3.10 (2023-04-09)
3.9 (2022-10-11)
3.8 (2022-10-07)
3.7 (2018-12-13)
3.6 (2018-12-11)
3.5 (2018-06-07)
3.4 (2018-04-27)
3.3 (2018-04-27)
3.2 (2018-04-27)
3.1 (2018-04-27)
3.0 (2018-04-24)
2.0 (2018-03-24)
/var/lib/buttervolumeconfig.ini fileVolumeDriver.Capabilities and just return 'local'1.4 (2018-02-01)
btrfs filesystem sync1.3.1 (2017-10-22)
1.3 (2017-07-30)
1.2 (2017-07-16)
1.1 (2017-07-13)
1.0 (2017-05-24)
FAQs
Docker plugin to manage Docker Volumes as BTRFS subvolumes
We found that buttervolume demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 2 open source maintainers collaborating on the project.
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