Barman

When an instance has the barman role in config.yml , TPA configures the instance as a Barman server to take backups of any other instances that name it in their backup setting.

instances:

- Name: one
  backup: two
  …


- Name: two
  role:
  - barman
  …

Multiple postgres instances can have the same Barman server named as their backup . Any postgres instance can have a list of Barman servers named as its backup . In this case, backups are taken to all of the named servers.

The default Barman configuration connects to PostgreSQL using pg_receivewal to take continuous backups of WAL. It takes a full backup of the instance using rsync over ssh twice weekly. Full backups and WAL are retained for long enough to enable recovery to any point in the previous 4 weeks.

Barman configuration

On each Barman server, a global configuration file is created as /etc/barman.conf . This file contains default values for many Barman configuration variables. For each Postgres server being backed up, an additional Barman configuration file is created. For example, to back up the server one , the file is /etc/barman.d/one.conf , and the backups are stored in /var/lib/barman/one . The file and directory names are taken from the backed-up instance’s backup_name setting. The default for this setting is the instance name.

You can set the following variables on the backed-up instance. They are passed through into Barman’s configuration with the prefix barman_ removed.

Variable	Default
barman_archiver	false
barman_log_file	/var/log/barman.log
barman_backup_method	rsync
barman_compression	pigz
barman_reuse_backup	link
barman_parallel_jobs	1
barman_backup_options	concurrent_backup
barman_immediate_checkpoint	false
barman_network_compression	false
barman_basebackup_retry_times	3
barman_basebackup_retry_sleep	30
barman_minimum_redundancy	3
barman_retention_policy	RECOVERY WINDOW OF 4 WEEKS
barman_last_backup_maximum_age	1 WEEK
barman_pre_archive_retry_script
barman_post_backup_retry_script
barman_post_backup_script
barman_streaming_wals_directory

Backup scheduling

TPA installs a cron job in /etc/cron.d/barman that runs every minute and invokes barman cron to perform maintenance tasks.

For each instance being backed up, TPA installs another cron job in /etc/cron.d/<backup_name> that takes the backups of that instance. This job runs as determined by the barman_backup_interval variable for the instance. The default is to take backups at 04:00 every Wednesday and Saturday.

SSH keys

TPA generates ssh key pairs for the postgres and barman users and installs them into the respective ~/.ssh directories. Keys for the postgres user are added to the barman authorized_keys file, and keys for the barman user are added to the postgres authorized_keys file. The postgres user must be able to ssh to the Barman server to archive WAL segments (if configured), and the barman user must be able to ssh to the Postgres instance to take or restore backups.