doc/cephadm: document recommended syntax for mounting files with ECA

Mounting files with extra container args seems to not
work with some of the more intuitive syntaxes.
See https://tracker.ceph.com/issues/57338

Signed-off-by: Adam King <adking@redhat.com>
(cherry picked from commit f577d1117d9a05c31819b2c7158d604482c9addf)

diff --git a/doc/cephadm/services/index.rst b/doc/cephadm/services/index.rst
index d6520ea407f8fe6c5e0a41fc52f8ae0cf682ac5d..d5b45d20c08103cf52bb1b42c4d4a3611c48e708 100644 (file)
--- a/doc/cephadm/services/index.rst
+++ b/doc/cephadm/services/index.rst
@@ -518,10 +518,32 @@ a spec like
         - host2
         - host3
     extra_container_args:
-      -  "--cpus=2"
+      - "--cpus=2"
 
 which would cause each mon daemon to be deployed with `--cpus=2`.
 
+Mounting Files with Extra Container Arguments
+---------------------------------------------
+
+A common use case for extra container arguments is to mount additional
+files within the container. However, some intuitive formats for doing
+so can cause deployment to fail (see https://tracker.ceph.com/issues/57338).
+The recommended syntax for mounting a file with extra container arguments is:
+
+.. code-block:: yaml
+
+    extra_container_args:
+      - "-v"
+      - "/absolute/file/path/on/host:/absolute/file/path/in/container"
+
+For example:
+
+.. code-block:: yaml
+
+    extra_container_args:
+      - "-v"
+      - "/opt/ceph_cert/host.cert:/etc/grafana/certs/cert_file:ro"
+
 Custom Config Files
 ===================