added ENTRYPOINT_EXEC

Containerfile

@@ -3,6 +3,7 @@ FROM ${os.image.prefix}${os.image.name}:${os.image.version}${os.image.suffix}
 
 ENV SKIP_ENTRYPOINT_SCRIPTS=false
 ENV VERBOSE=true
+ENV ENTRYPOINT_EXEC=
 
 # these are effectively immutable; provided to be used by extending images
 # the entrypoint will re-set these in case they are changed

README.md

@@ -15,6 +15,8 @@ The following tools are available.
 
 This image provides an entrypoint script that executes other entrypoint scripts, before executing the `CMD` (if provided).  It will execute any executable `.sh` scripts added to the path described by the `CONTAINERD_ENTRYPOINT_PATH` environment variable.  It will execute them in default sort order, so the use of numerical prefixes (`00_first.sh` or `99_last.sh`) may be wise.
 
+You may also provide an `ENTRYPOINT_EXEC` to prefix all `CMD` executions in the entrypoint.  For instance, you could use `ENTRYPOINT_EXEC=java` so container executions would always be executing `java`.
+
 ### Extensible Certificate Authority
 
 This image detects files in the path described by the `CACERT_INSTALL_PATH` environment variable.  If a file is found, it will treat it as a certificate and add it to the trusted certificates in all supported contexts.
@@ -26,6 +28,7 @@ This image detects files in the path described by the `CACERT_INSTALL_PATH` envi
 | Name                         | Default         | Mutable |
 | ---------------------------- | --------------- |:-------:|
 | `SKIP_ENTRYPOINT_SCRIPTS`    | `false`         | Yes     |
+| `ENTRYPOINT_EXEC`            | *none*          | Yes     |
 | `VERBOSE`                    | `true`          | Yes     |
 | `CONTAINERD_ENTRYPOINT_PATH` | *not important* | No      |
 | `CACERT_INSTALL_PATH`        | *not important* | No      |

src/main/containerd/entrypoint.sh

@@ -35,7 +35,12 @@ if ! find ${CACERT_INSTALL_PATH}/ -maxdepth 0 -empty | read JUNK; then
     update-ca-certificates
 fi
 
-if [[ ! -z $1 ]]; then
+if [[ -z ${ENTRYPOINT_EXEC} ]]; then
+    if [[ ! -z $1 ]]; then
+        ifecho "Executing command ..."
+        exec "$@"
+    fi
+else
     ifecho "Executing command ..."
-    exec "$@"
+    exec "${ENTRYPOINT_EXEC} $@"
 fi