docs(docker): usage and labels for falco-tester docker image

Signed-off-by: Leonardo Di Donato <leodidonato@gmail.com>

docker/tester/Dockerfile

@@ -1,5 +1,9 @@
 FROM centos:7
 
+LABEL name="falcosecurity/falco-tester"
+LABEL usage="docker run -v /boot:/boot:ro -v /var/run/docker.sock:/var/run/docker.sock -v $PWD/..:/source -v $PWD/build:/build -e FALCO_VERSION=<current_falco_version> --name <name> falcosecurity/falco-tester test"
+LABEL maintainer="opensource@sysdig.com"
+
 ENV FALCO_VERSION=
 ENV BUILD_TYPE=release
 

docker/tester/root/usr/bin/entrypoint

@@ -27,13 +27,14 @@ case "$CMD" in
         echo "Missing Falco version." >&2
         exit 1
     fi
-    if [ ! -f "$BUILD_DIR/$BUILD_TYPE/falco-$FALCO_VERSION-x86_64.deb" ]; then
+    PACKAGE="$BUILD_DIR/$BUILD_TYPE/falco-$FALCO_VERSION-x86_64.deb"
+    if [ ! -f "$PACKAGE" ]; then
         echo "Package(s) not found." >&2
         exit 1
     fi
     DOCKER_IMAGE_NAME="falcosecurity/falco:test"
     echo "Building local docker image $DOCKER_IMAGE_NAME from latest debian package..."
-    cp "$BUILD_DIR/$BUILD_TYPE/falco-$FALCO_VERSION-x86_64.deb" $BUILD_DIR/$BUILD_TYPE/docker/local
+    cp "$PACKAGE" $BUILD_DIR/$BUILD_TYPE/docker/local
     cd $BUILD_DIR/$BUILD_TYPE/docker/local
     docker build --build-arg FALCO_VERSION="$FALCO_VERSION" -t "$DOCKER_IMAGE_NAME" .
 

docker/tester/root/usr/bin/usage

@@ -1,17 +1,38 @@
 #!/usr/bin/env bash
 
+pythonversion=$(python -c 'import sys; version=sys.version_info[:3]; print("{0}.{1}.{2}".format(*version))')
+pipversion=$(pip --version | cut -d' ' -f 1,2,5,6)
+dockerversion=$(docker --version)
+
 cat <<EOF
 Hello, this is the Falco tester container.
 
 How to use.
 
-    ...
+    The default commands for the Falco tester image reports usage and environment info.
+    * docker run falcosecurity/falco-tester
+    * docker run falcosecurity/falco-tester usage
+
+    It supports bash.
+    * docker run -ti falcosecurity/falco-tester:chore-travis bash
+
+    To run Falco regression tests you need to provide:
+    - the docker socket
+    - the boot directory
+    - the source directory
+    - the directory where Falco has been built
+    - the environment variable FALCO_VARIABLE set to the value obtained during the Falco's build
+
+    Assuming you are running it from the Falco root directory, you can run it as follows.
+    * docker run -v /boot:/boot:ro -v /var/run/docker.sock:/var/run/docker.sock -v $PWD/..:/source -v $PWD/build:/build -e FALCO_VERSION=<current_falco_version> falcosecurity/falco-tester test
 
 How to build.
 
-    ...
+    * cd docker/builder && DOCKER_BUILDKIT=1 docker build -t falcosecurity/falco-tester .
 
 Environment.
 
-    * ...
+    * python ${pythonversion}
+    * ${pipversion}
+    * ${dockerversion}
 EOF