Backing up your database with barman

Barman is "an open-source administration tool for disaster recovery of PostgreSQL servers". The files in this directory are used to build the tbeadle/postgres:<version>-barman docker images. These images are like the non--barman ones except that they are tuned to work closely with a barman server, supporting the streaming of WAL logs and incremental base backups using rsync over ssh. These are handled by the following changes to the base images:

The following additional packages are installed:
- openssh-server - For allowing SSH connections from the remote barman server for management and fetching base backups.
- rsync - To allow the barman server to take incremental base backups, saving on storage on the barman server.
- supervisor - To manage the postgres and sshd processes.

The following environment variables are allowed to be defined:

Variable name	Description
BARMAN_USER	This user is created as a superuser in the database during initialization. It is the user that barman should be connecting as for its management operations. Defaults to `barman`.
BARMAN_PASSWORD	The password that gets set for the `BARMAN_USER`. Defaults to no password. NOTE: You are strongly encouraged to use a password for this superuser account. The user is allowed to connect from anywhere and, with no password set, anyone could log in as a superuser to your database by knowing just the username.
BARMAN_PUBKEY	The path in the container to an SSH public key that is paired with the private key that the barman server will use when connecting over SSH. This will be copied to the location of the `authorized_keys` file for the `postgres` user on this server. The barman server will therefore need to SSH as `postgres`. If this file does not exist, then taking base backups over rsync will not work. Defaults to `/private/barman.id_rsa.pub`.
BARMAN_SLOT_NAME	The name of the replication slot used by barman for streaming WAL logs. The slot will be created when the database is initialized. Defaults to `barman`.
SSH_HOST_KEY	The path in the container to a private host key that should be used for sshd. If it exists, it will be copied to `/etc/ssh/` and configured as the only host key in `sshd_config`. The barman server can then have a `known_hosts` file containing the corresponding public key to validate that it's connecting to the correct database server when making SSH connections. If the file does not exist, SSH host keys will automatically be generated. Defaults to `/private/ssh_host_rsa_key`.
STREAMING_USER	This user is created in the database with REPLICATION privileges. It will be used for streaming WAL logs from the database to the barman server. Defaults to `streaming_barman`.
STREAMING_PASSWORD	The password that gets set for the `STREAMING_USER`. Defaults to no password. NOTE: You are strongly encouraged to use a password for this account. The user is allowed to connect from anywhere and, with no password set, anyone could log in with replication privileges to your database by knowing just the username.

When starting a container using this image, supervisor will run as the init process. It will store the stdout and stderr logs for sshd and postgres under /var/log/supervisor/{sshd,postgres}/.
The postgresql.conf file is modified to set wal_level, max_wal_senders, and max_replication_slots to values suitable for working with barman.

See the examples in https://github.com/tbeadle/docker-barman for examples on how to use this image with that barman image.

Building the images

If you make any changes to the Dockerfile.template or supporting files, run ./update.sh. Then to build all of the images, simply run:

docker-compose build

To build the image for a single postgres version, just run it like the following for 9.6:

docker-compose build pg9_6

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