docker

Author: lerndevopss

docker/images/cmd-vs-entrypoint.md

@@ -0,0 +1,72 @@
+Dockerfile:
+
+FROM debian:wheezy
+ENTRYPOINT ["/bin/ping"]
+CMD ["localhost"]
+
+Execution: 
+Docker build -t test .
+Docker run -d test
+Docker run -it test google.com
+
+
+
+
+Dockerfile:
+FROM debian:wheezy
+CMD ["/bin/ping", "localhost"]
+
+Execution:
+Docker build -t test2 .
+Docker run test2
+Docker run test2 bash
+
+
+The ENTRYPOINT specifies a command that will always be executed when the container starts. The CMD specifies arguments that will be fed to the ENTRYPOINT.
+
+
+
+
+Both CMD and ENTRYPOINT instructions define what command gets executed when running a container. There are few rules that describe their co-operation.
+	1.	Dockerfile should specify at least one of CMD or ENTRYPOINT commands.
+	2.	ENTRYPOINT should be defined when using the container as an executable.
+	3.	CMD should be used as a way of defining default arguments for an ENTRYPOINT command or for executing an ad-hoc command in a container.
+	4.	CMD will be overridden when running the container with alternative arguments
+
+
+
+CMD
+╔════════════════════════════╦═════════════════════════════╗
+║ No CMD                     ║ error, not allowed          ║
+╟────────────────────────────╫─────────────────────────────╢
+║ CMD [“exec_cmd”, “p1_cmd”] ║ exec_cmd p1_cmd             ║
+╟────────────────────────────╫─────────────────────────────╢
+║ CMD [“p1_cmd”, “p2_cmd”]   ║ p1_cmd p2_cmd               ║
+╟────────────────────────────╫─────────────────────────────╢
+║ CMD exec_cmd p1_cmd        ║ /bin/sh -c exec_cmd p1_cmd  ║
+╚════════════════════════════╩═════════════════════════════╝
+
+-- ENTRYPOINT exec_entry p1_entry
+╔════════════════════════════╦══════════════════════════════════╗
+║ No CMD                     ║ /bin/sh -c exec_entry p1_entry   ║
+╟────────────────────────────╫──────────────────────────────────╢
+║ CMD [“exec_cmd”, “p1_cmd”] ║ /bin/sh -c exec_entry p1_entry   ║
+╟────────────────────────────╫──────────────────────────────────╢
+║ CMD [“p1_cmd”, “p2_cmd”]   ║ /bin/sh -c exec_entry p1_entry   ║
+╟────────────────────────────╫──────────────────────────────────╢
+║ CMD exec_cmd p1_cmd        ║ /bin/sh -c exec_entry p1_entry   ║
+╚════════════════════════════╩══════════════════════════════════╝
+
+-- ENTRYPOINT [“exec_entry”, “p1_entry”]
+╔════════════════════════════╦═════════════════════════════════════════════════╗
+║ No CMD                     ║ exec_entry p1_entry                             ║
+╟────────────────────────────╫─────────────────────────────────────────────────╢
+║ CMD [“exec_cmd”, “p1_cmd”] ║ exec_entry p1_entry exec_cmd p1_cmd             ║
+╟────────────────────────────╫─────────────────────────────────────────────────╢
+║ CMD [“p1_cmd”, “p2_cmd”]   ║ exec_entry p1_entry p1_cmd p2_cmd               ║
+╟────────────────────────────╫─────────────────────────────────────────────────╢
+║ CMD exec_cmd p1_cmd        ║ exec_entry p1_entry /bin/sh -c exec_cmd p1_cmd  ║
+╚════════════════════════════╩═════════════════════════════════════════════════╝
+
+
+

docker/images/dockerfile_myapp

@@ -2,10 +2,13 @@ FROM ubuntu
 RUN apt-get -y update 
 RUN apt-get -y install openjdk-8-jdk wget
 RUN mkdir /opt/tomcat
-COPY tomcat-8.5.37.tar.gz /tmp 
-RUN cd /tmp && tar xvfz tomcat-8.5.37.tar.gz
-RUN cp -Rv /tmp/apache-tomcat-8.5.37/* /opt/tomcat/
-RUN rm /tmp/tomcat-8.5.37.tar.gz
+# COPY tomcat-8.5.37.tar.gz /tmp
+# RUN cd /tmp && tar xvfz tomcat-8.5.37.tar.gz
+# RUN mv /tmp/apache-tomcat-8.5.37/* /opt/tomcat/
+# RUN rm /tmp/tomcat-8.5.37.tar.gz
+ADD tomcat-8.5.37.tar.gz /tmp
+RUN mv /tmp/apache-tomcat-8.5.37/* /opt/tomcat/
 COPY myapp.war /opt/tomcat/webapps
 EXPOSE 8080
-CMD /opt/tomcat/bin/catalina.sh run
+ENTRYPOINT ["/opt/tomcat/bin/catalina.sh", "run"]  ## JSON Format
+# ENTRYPOINT /opt/tomcat/bin/catalina.sh run  ## Shell Format

docker/images/dockerfile_nginx2

@@ -1,4 +1,2 @@
 FROM nginx 
 COPY index.html /var/www/html
-EXPOSE 80
-ENTRYPOINT /usr/sbin/nginx -g 'daemon off;'

kube/pods/pod.yml

@@ -4,6 +4,7 @@ metadata:
   name: tomcatpod
   labels:
     app: MyApp
+  namespace: dev
 spec:
   containers:
   - name: tomcat