1.You need to create docker file first.Below is example of small test docker file.
root@deb-VirtualBox:~# cat test_docker.file FROM centos:latest RUN yum update -y
Here please note that FROM clause denotes first we need to pull centos image and RUN clause will run yum update on top of it.
2.Now I will build the docker image .
-t option is used to provide tag name
-f option is used to provide docker file name.
You need to run the following command from same path where your docker file resides.
root@deb-VirtualBox:~# docker build -t customimage:v1 -f test_docker.file .
Sending build context to Docker daemon 8.704kB
Step 1/2 : FROM centos:latest
latest: Pulling from library/centos
469cfcc7a4b3: Pull complete
Digest: sha256:989b936d56b1ace20ddf855a301741e52abca38286382cba7f44443210e96d16
Status: Downloaded newer image for centos:latest
---> e934aafc2206
Step 2/2 : RUN yum update -y
---> Running in 21686d3260e4
Loaded plugins: fastestmirror, ovl
http://ftp.iitm.ac.in/centos/7.4.1708/updates/x86_64/repodata/repomd.xml: [Errno 12] Timeout on http://ftp.iitm.ac.in/centos/7.4.1708/updates/x86_64/repodata/repomd.xml: (28, 'Connection timed out after 30001 milliseconds')
Trying other mirror.
Determining fastest mirrors
* base: mirror.nbrc.ac.in
* extras: mirror.nbrc.ac.in
* updates: mirror.nbrc.ac.in
No packages marked for update
Removing intermediate container 21686d3260e4
---> 9528f83769a3
Successfully built 9528f83769a3
Successfully tagged customimage:v1
3.Now let me run the docker image command to check details of our latest build
root@deb-VirtualBox:~# docker images
Please note centos image has been pulled and on top of it our customimage has been built.
4.Now you can use no-cache during pull the image
root@deb-VirtualBox:~# docker build --pull --no-cache -t optimized:v1 -f test_docker.file .
Sending build context to Docker daemon 8.704kB
Step 1/2 : FROM centos:latest
latest: Pulling from library/centos
Digest: sha256:989b936d56b1ace20ddf855a301741e52abca38286382cba7f44443210e96d16
Status: Image is up to date for centos:latest
---> e934aafc2206
Step 2/2 : RUN yum update -y
---> Running in b2319a7d1d89
Loaded plugins: fastestmirror, ovl
http://ftp.iitm.ac.in/centos/7.4.1708/updates/x86_64/repodata/repomd.xml: [Errno 12] Timeout on http://ftp.iitm.ac.in/centos/7.4.1708/updates/x86_64/repodata/repomd.xml: (28, 'Connection timed out after 30001 milliseconds')
Trying other mirror.
Determining fastest mirrors
* base: del-mirrors.extreme-ix.org
* extras: del-mirrors.extreme-ix.org
* updates: del-mirrors.extreme-ix.org
No packages marked for update
Removing intermediate container b2319a7d1d89
---> dd055168eb91
Successfully built dd055168eb91
Successfully tagged optimized:v1
5.Now let me write complex docker file
root@deb-VirtualBox:~# cat mycomplexdockerfile.file
FROM centos:6
LABEL maintainer="debasis.tcs@gmail.com"
RUN yum update -y && yum install -y httpd net-tools
RUN mkdir -p /run/httpd
RUN rm -rf /run/http/* /tmp/httpd*
CMD echo "Remember to check your container IP address"
ENV ENVIRONMENT="production"
EXPOSE 80
ENTRYPOINT apachectl "-DFOREGROUND"
6.Let me explain the syntex which we used above
FROM centos:6 (This will pull centos image as base)
LABEL maintainer=”debasis.tcs@gmail.com” (This is deprecated)
RUN yum update -y && yum install -y httpd net-tools(It will run all yum package install command)
RUN mkdir -p /run/httpd (Create directory)
RUN rm -rf /run/http/* /tmp/httpd* (Remove directory)
CMD echo “Remember to check your container IP address” (Echo something important)
ENV ENVIRONMENT=”production” (Setting env variable)
EXPOSE 80 (The apache service will listener to port 80)
ENTRYPOINT apachectl “-DFOREGROUND”
7.Building docker image
docker build -t mywebserver:v1 -f mycomplexdockerfile.file .
8.Please check the image again
root@deb-VirtualBox:~# docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
mywebserver v1 a23dab42b0ee 7 minutes ago 321MB
optimized v1 dd055168eb91 11 hours ago 301MB
customimage v1 9528f83769a3 11 hours ago 301MB
hello-world latest e38bc07ac18e 2 weeks ago 1.85kB
centos 6 70b5d81549ec 3 weeks ago 195MB
centos latest e934aafc2206 3 weeks ago 199MB
root@deb-VirtualBox:~# docker run -d --name mytestweb --rm mywebserver:v1
c0d3e30d1ab22523e7be4958f15cad6dca122a368306a23dd1573a958adabebd
9.Please check that docker is running now
root@deb-VirtualBox:~# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
c0d3e30d1ab2 mywebserver:v1 "/bin/sh -c 'apachec…" 45 seconds ago Up 44 seconds 80/tcp mytestweb
10.Let me check IP address of the docker
root@deb-VirtualBox:~# docker inspect mytestweb | grep -i ipaddress
"SecondaryIPAddresses": null,
"IPAddress": "172.17.0.2",
"IPAddress": "172.17.0.2",
11.Let me check using elinks
root@deb-VirtualBox:~# elinks http://172.17.0.2
12.Now we can use argument in docker file
root@deb-VirtualBox:~# cat mycomplexdockerfile_arg.file
ARG TARGETVERSION=6
FROM centos:${TARGETVERSION}
LABEL maintainer="debasis.tcs@gmail.com"
RUN yum update -y && yum install -y httpd net-tools
RUN mkdir -p /run/httpd
RUN rm -rf /run/http/* /tmp/httpd*
CMD echo "Remember to check your container IP address"
ENV ENVIRONMENT="production"
EXPOSE 80
ENTRYPOINT apachectl "-DFOREGROUND"
13.I will again re-build the docker
root@deb-VirtualBox:~# docker build -t mywebserver1:v1 -f mycomplexdockerfile_arg.file .
14.We can check history of command executed in docker build
root@deb-VirtualBox:~# docker image history mywebserver1:v1
15.You may use no-trunc option to see full command line used in docker run
