matrix-base: make Synology shared-mount volume configurable

Replace the hardcoded /volume1 path with a matrix_base_synology_volume_path
variable (defaulting to /volume1), used both by the setup-time prerequisites
task and by the boot-fix recovery script. This keeps the path consistent with
the rest of the configuration and lets users on a non-default Docker storage
volume override it.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

roles/custom/matrix-base/defaults/main.yml

@@ -210,6 +210,11 @@ matrix_synology_user_password: ""
 # system Python interpreter (ansible_python_interpreter) on the remote host.
 matrix_base_synology_requests_version_constraint: "requests<2.32"
 
+# Synology volume that needs shared mount propagation so that Docker
+# bind-propagation=slave mounts (used by matrix-synapse for its media store)
+# work correctly. Defaults to /volume1 (DSM's default Docker storage volume).
+matrix_base_synology_volume_path: "/volume1"
+
 matrix_base_data_path: "/matrix"
 matrix_base_data_path_mode: "750"
 

roles/custom/matrix-base/tasks/setup_synology_prerequisites.yml

@@ -13,8 +13,8 @@
 # step. The boot-fix service handles this on every subsequent reboot.
 # noqa command-instead-of-module: ansible.builtin.mount does not support
 # changing mount propagation (--make-shared); command is the only option here.
-- name: Ensure /volume1 has shared mount propagation (Synology)
-  ansible.builtin.command: mount --make-shared /volume1  # noqa command-instead-of-module
+- name: Ensure the Synology volume has shared mount propagation
+  ansible.builtin.command: mount --make-shared {{ matrix_base_synology_volume_path }}  # noqa command-instead-of-module
   changed_when: false
 
 - ansible.builtin.include_tasks: "{{ role_path }}/tasks/setup_synology_boot_fix.yml"

roles/custom/matrix-base/templates/bin/matrix-synology-boot-fix.j2

@@ -8,7 +8,7 @@
 # This script runs after multi-user.target (outside Container Manager's dependency
 # chain) and does two things:
 #
-# 1. Makes /volume1 mount-shared so Docker bind-propagation=slave mounts work.
+# 1. Makes {{ matrix_base_synology_volume_path }} mount-shared so Docker bind-propagation=slave mounts work.
 #    Inserting this into the systemd chain Before=pkg-ContainerManager-dockerd.service
 #    causes Container Manager to detect a broken dependency and prompt for repair,
 #    so it must run here instead, after Docker is already up.
@@ -32,12 +32,12 @@ if ! {{ devture_systemd_docker_base_host_command_docker }} info >/dev/null 2>&1;
     exit 1
 fi
 
-# Make /volume1 shared so Docker bind-propagation=slave mounts work correctly.
+# Make {{ matrix_base_synology_volume_path }} shared so Docker bind-propagation=slave mounts work correctly.
 # Must run after Docker is up to avoid interfering with Container Manager's
 # integrity checks, but before matrix-synapse (and any other service using
 # bind-propagation=slave) creates its containers.
-/bin/mount --make-shared /volume1
-echo "matrix-synology-boot-fix: /volume1 set to shared mount propagation"
+/bin/mount --make-shared {{ matrix_base_synology_volume_path }}
+echo "matrix-synology-boot-fix: {{ matrix_base_synology_volume_path }} set to shared mount propagation"
 
 # Start any enabled matrix-*.service that is inactive or failed.
 # Both states indicate the service did not come up at boot — either skipped by