Re: failed to setup barman backup when Posgres is running in Podman Container

I don’t have experience with Barman but if in-container tooling is limited you may try the following:

* Map postgre’s uid:gid with same numbers as barman’s when mounting volumes. Check –volume idmap option https://docs.podman.io/en/latest/markdown/podman-run.1.html#volume-v-source-volume-host-dir-container-dir-options
--uidmap and --gidmap may be useful too
* Run a Temporal or side container (root) that copies it for you.
* Run a postgresql server container with ssh and rsync packages, still postgres will have to know about ‘external’ barman user

From: duc hiep ha <haduchiep(at)googlemail(dot)com>
Date: Thursday, 11 January 2024 at 10:13
To: pgsql-admin(at)lists(dot)postgresql(dot)org <pgsql-admin(at)lists(dot)postgresql(dot)org>
Subject: Fwd: failed to setup barman backup when Posgres is running in Podman Container

Dear All,

I am trying to use Barman to back up PostgreSQL, which is running in a Podman container. However, I encounter the error "WAL archive: FAILED," as shown below:
#barman check testdb
Server testdb:
WAL archive: FAILED (please make sure WAL shipping is set up)
PostgreSQL: OK
superuser: OK
PostgreSQL streaming: OK
wal_level: OK
replication slot: OK
directories: OK
retention policy settings: OK
backup maximum age: OK (no last_backup_maximum_age provided)
compression settings: OK
failed backups: OK (there are 0 failed backups)
minimum redundancy requirements: OK (have 0 backups, expected at least 0)
pg_basebackup: OK
pg_basebackup compatible: OK
pg_basebackup supports tablespaces mapping: OK
pg_receivexlog: OK
pg_receivexlog compatible: OK
receive-wal running: OK
archiver errors: OK

I have identified that normally, when the PostgreSQL database is installed on a regular VM (not in a container), the archive_command parameter under postgresql.conf looks like this:
archive_command = 'rsync -a %p barman(at)barman-backup-server-ip:/data/barman/main-db-server/incoming/%f'
However, when PostgreSQL is installed on a Podman container, I cannot use the above archive_command because within the PostgreSQL container, it doesn't understand rsync, ssh, and the barman user. That's why I have to use a normal copy command like:

archive_command = 'cp -i %p /srv/archive/%f'
I then mounted this wal-files folder on '/data/barman/main-db-server/incoming/%f'. As a result, all these wal_files have the PostgreSQL ownership and not the barman ownership. The barman user has no privileges to change these wal-files, which is why the WAL archive is marked as FAILED.

Do you know how to solve this issue? do I have to install Barman and PostgreSQL in the same Pod container in order to backup PostgreSQL container? Or is there another solution to this problem?

Thank you for your support in advance.

Best,
Ha