TASK [galaxy/postgres : Execute Postgres managed database initialization SQL file for synapse] : 'psql: error: connection to server at "matrix-postgres" (192.168.64.2), port 5432 failed: FATAL: password authentication failed for user "matrix"'

[Verymadlibrarian]

Describe the bug
While installing for the first time, "Postgres managed database initialization SQL file for synapse" apparently fails.

To Reproduce
My vars.yml file looks like this:

---
# The bare domain name which represents your Matrix identity.
# Matrix user ids for your server will be of the form (`@user:<matrix-domain>`).
#
# Note: this playbook does not touch the server referenced here.
# Installation happens on another server ("matrix.<matrix-domain>").
#
# If you've deployed using the wrong domain, you'll have to run the Uninstalling step,
# because you can't change the Domain after deployment.
#
# Example value: example.com
matrix_domain: X.com

# The Matrix homeserver software to install.
# See:
#  - `roles/custom/matrix-base/defaults/main.yml` for valid options
# - the `docs/configuring-playbook-IMPLEMENTATION_NAME.md` documentation page, if one is available for your implementation choice
matrix_homeserver_implementation: synapse

# A secret used as a base, for generating various other secrets.
# You can put any string here, but generating a strong one is preferred (e.g. `pwgen -s 64 1`).
matrix_homeserver_generic_secret_key: 'X'

# By default, the playbook manages its own Traefik (https://doc.traefik.io/traefik/) reverse-proxy server.
# It will retrieve SSL certificates for you on-demand and forward requests to all other components.
# For alternatives, see `docs/configuring-playbook-own-webserver.md`.
matrix_playbook_reverse_proxy_type: playbook-managed-traefik

# This is something which is provided to Let's Encrypt when retrieving SSL certificates for domains.
#
# In case SSL renewal fails at some point, you'll also get an email notification there.
#
# If you decide to use another method for managing SSL certificates (different than the default Let's Encrypt),
# you won't be required to define this variable (see `docs/configuring-playbook-ssl-certificates.md`).
#
# Example value: someone@example.com
traefik_config_certificatesResolvers_acme_email: 'elonbigiq@x.com'

# A Postgres password to use for the superuser Postgres user (called `matrix` by default).
#
# The playbook creates additional Postgres users and databases (one for each enabled service)
# using this superuser account.
postgres_connection_password: 'X'

matrix_static_files_container_labels_base_domain_enabled: true
# By default, we configure Coturn's external IP address using the value specified for `ansible_host` in your `inventory/hosts` file.
# If this value is an external IP address, you can skip this section.
#
# If `ansible_host` is not the server's external IP address, you have 2 choices:
# 1. Uncomment the line below, to allow IP address auto-detection to happen (more on this below)
# 2. Uncomment and adjust the line below to specify an IP address manually
#
# By default, auto-detection will be attempted using the `https://ifconfig.co/json` API.
# Default values for this are specified in `matrix_coturn_turn_external_ip_address_auto_detection_*` variables in the Coturn role
# (see `roles/custom/matrix-coturn/defaults/main.yml`).
#
# If your server has multiple IP addresses, you may define them in another variable which allows a list of addresses.
# Example: `matrix_coturn_turn_external_ip_addresses: ['1.2.3.4', '4.5.6.7']`
#
# matrix_coturn_turn_external_ip_address: ''

To reproduce :
Install Debian 12 on x64 platform with kernel version 6.1.0-25-amd64.
Install docker
Clone the repo
Populate vars.yml and hosts with basic configuration.
Start the installation with "ansible-playbook -i inventory/hosts setup.yml --tags=install-all,ensure-matrix-users-created,start"

Expected behavior
Matrix being installed without error. No postgres connection/password errors

Matrix Server:

• OS: Debian 12
• Architecture amd64

Additional context
Here is the error output

TASK [galaxy/postgres : Execute Postgres managed database initialization SQL file for synapse] *************************
fatal: [X.com]: FAILED! => changed=true
  cmd:
  - /usr/bin/env
  - docker
  - run
  - --rm
  - --user=999:1001
  - --cap-drop=ALL
  - --env-file=/matrix/postgres/env-postgres-psql
  - --network=matrix-postgres
  - --mount
  - type=bind,src=/tmp/matrix-postgres-init-managed-db-user-and-role.sql,dst=/matrix-postgres-init-managed-db-user-and-role.sql,ro
  - --entrypoint=/bin/sh
  - docker.io/postgres:16.4-alpine
  - -c
  - psql -h matrix-postgres --file=/matrix-postgres-init-managed-db-user-and-role.sql
  delta: '0:00:00.800244'
  end: '2024-09-30 11:29:05.581487'
  msg: non-zero return code
  rc: 2
  start: '2024-09-30 11:29:04.781243'
  stderr: 'psql: error: connection to server at "matrix-postgres" (192.168.64.2), port 5432 failed: FATAL:  password authentication failed for user "matrix"'
  stderr_lines: <omitted>
  stdout: ''
  stdout_lines: <omitted>

[DeastinY]

for me the problem orginated from having had setup synapse with another psql password before (like, months before) and then I changed the password. Maybe it helps you