Docker by Example - Basics

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Docker by Example
Ganesh & Hari
ganesh@codeops.tech
hari@codeops.tech
Using a Visual Approach

What is Docker?
Docker is an open-source project that automates the deployment of
applications inside software containers.

What is Docker?
“an open platform for developers and sysadmins to build, ship, and run
distributed applications”

What is Docker?
Source: https://en.wikipedia.org/wiki/Docker_(software)

Pop quiz
Docker is written in:
A. Java language
B. C language
C. D language
D. Go language

Pop quiz: answer
Docker is written in
Go language
Good read: Why Did We Decide to Write Docker in Go?

VMs vs. containers
Simulates a physical machine
Provides a local ﬁle system
Can be accessed over a network
Full and independent guest operating system
Virtualized device drivers
Strong resource and memory management
Huge memory foot-print
Needs a hypervisor

Docker accesses virtualisation features of Linux

Native Docker support on Windows
Source: https://i2.wp.com/blog.docker.com/wp-content/uploads/windows.png?w=975&ssl=1
https://i2.wp.com/blog.docker.com/wp-content/uploads/windows.png?w=975&ssl=1

Docker becoming popular over time
Google Trends: https://www.google.co.uk/trends/explore?q=%2Fm%2F0wkcjgj&hl=en-US

What’s covered in this session?

Installing Docker
Install it from “https://www.docker.com/products/overview"

Official Docker images?
From “https://hub.docker.com/explore/"

How to find my Docker version?
$ docker -v
Docker version 1.12.0-rc4, build e4a0dbc, experimental

Finding details of a Docker installation

Can I install Docker from commandline?
Yes! from get.docker.com
# This script is meant for quick & easy install via:
# 'curl -sSL https://get.docker.com/ | sh'
# or:
# 'wget -qO- https://get.docker.com/ | sh'

How to do “hello world” in Docker?
$ docker run docker/whalesay cowsay Hello world

$ docker run docker/whalesay cowsay "Hello world"
Runs a command
in a new container
Base image for
creating the container
Command name to
run within the container
Argument to the
“cowsay” command

$ docker run -it hello-world
$ docker run -it hello-world
Hello from Docker!
This message shows that your installation appears to be working correctly.
To generate this message, Docker took the following steps:
1. The Docker client contacted the Docker daemon.
2. The Docker daemon pulled the "hello-world" image from the Docker Hub.
3. The Docker daemon created a new container from that image which runs the
executable that produces the output you are currently reading.
4. The Docker daemon streamed that output to the Docker client, which sent it
to your terminal.
To try something more ambitious, you can run an Ubuntu container with:
$ docker run -it ubuntu bash
Share images, automate workflows, and more with a free Docker Hub account:
https://hub.docker.com
For more examples and ideas, visit:
https://docs.docker.com/engine/userguide/

How to get help on commands to use?
Use “docker -h” command, as in:
$ docker -h
Usage: docker [OPTIONS] COMMAND [arg...]
docker [ --help | -v | --version ]
A self-sufficient runtime for containers.
Options:
--config=~/.docker Location of client config files
-D, --debug Enable debug mode
-H, --host=[] Daemon socket(s) to connect to
-h, --help Print usage
-l, --log-level=info Set the logging level
…
Commands:
attach Attach to a running container

Docker commands look like Linux commands - so
familiarity with Linux commands can really help to
get up to speed quickly with Docker.

How to get an image?
Use “docker pull <image_name>” command
In my case debian image was
already pulled. If it were not there,
Docker would have pulled it afresh

Choose smaller images
❖ Example: Choose Alpine vs. Fedora (5 MB vs. 205 MB)
alpine latest 4e38e38c8ce0 4 weeks ago 4.799 MB
fedora latest f9873d530588 4 weeks ago 204.4 MB
❖ Prefer choosing a smaller base image that provides
equivalent functionality (for your requirement) instead of
choosing a larger one

How to get details of an image?
Use “docker inspect <image_name>” command
docker inspect debian
[
{
"Id": "sha256:1b088884749bd93867ddb48ff404d4bbff09a17af8d95bc863efa5d133f87b78",
"RepoTags": [
"debian:latest"
],
"RepoDigests": [
"debian@sha256:8b1fc3a7a55c42e3445155b2f8f40c55de5f8bc8012992b26b570530c4bded9e"
],
"Parent": "",
"Comment": "",
"Created": "2016-06-09T21:28:43.776404816Z",
"Container": "2f3dcd897cf758418389d50784c73b43b1fd7db09a80826329496f05eef7b377",
"ContainerConfig": {
"Hostname": "6250540837a8",
"Domainname": "",
"User": "",
"AttachStdin": false,
"AttachStdout": false,
"AttachStderr": false,
"Tty": false,
"OpenStdin": false,
// ...

How to see “layers” in an image?
Use “docker history <image_name>” command
Each of these lines are layers and the
size column shows the exact size of
each layer in the image

Use tools to visualise layers
❖ You can use the online tool imagelayers.io to visualise the
layers of an image

How can I load and store images?
Use “docker save” and “docker load” commands

How do I delete an image?
Use “docker rmi <image-tag>”
$ docker images alpine
REPOSITORY TAG IMAGE ID CREATED SIZE
alpine latest 4e38e38c8ce0 4 weeks ago 4.799 MB
$ docker rmi alpine
Untagged: alpine:latest
Untagged: alpine@sha256:3dcdb92d7432d56604d4545cbd324b14e647b313626d99b889d0626de158f73a
$ docker images alpine

How to delete all docker images?
Use “$docker rmi $(docker images -q)”
docker images -q
lists all image ids

Avoid “image sprawl”
// output from the docker bench security tool
[INFO] 6.4 - Avoid image sprawl
[INFO] * There are currently: 60 images
❖ Remove unused images and release disk space

How to find “dangling images”?
Use “docker images -f "dangling=true"”
$ docker images -f "dangling=true"
<none> <none> 777f9424d24d 7 minutes ago 125.2 MB
<none> <none> 3d02168f00fc 12 days ago 34.22 MB
<none> <none> 0f192147631d 3 weeks ago 132.8 MB

Remove “dangling images”
❖ Remove “dangling images” using the command “$docker
rmi $(docker images -f "dangling=true" -q)”

How to push my image to Docker Hub?
$ docker tag myjavaapp gsamarthyam/myfirstjavaprog:latest
$ docker push gsamarthyam/myfirstjavaprog:latest
The push refers to a repository [docker.io/gsamarthyam/myfirstjavaprog]
a97e2e0314bc: Pushed
3b9964bc9417: Pushed
de174b528b56: Pushed
// elided the output
latest: digest: sha256:1618981552efb12afa4e348b9c0e6d28f0ac4496979ad0c0a821b43547e13c13 size: 2414
$

How to pull my image from Docker Hub?
$ docker pull gsamarthyam/myfirstjavaprog:latest
latest: Pulling from gsamarthyam/myfirstjavaprog
Digest: sha256:1618981552efb12afa4e348b9c0e6d28f0ac4496979ad0c0a821b43547e13c13
// output elided …
$ docker images
myjavaapp latest 0d7a3a12ba9d About an hour ago 669.2 MB
gsamarthyam/myfirstjavaprog latest 0d7a3a12ba9d About an hour ago 669.2 MB
// output elided …
$ docker run gsamarthyam/myfirstjavaprog
hello world
$

How do I create and use my own registry?
$ docker pull registry
Using default tag: latest
latest: Pulling from library/registry
e110a4a17941: Already exists
2ee5ed28ffa7: Pull complete
d1562c23a8aa: Pull complete
06ba8e23299f: Pull complete
802d2a9c64e8: Pull complete
Digest: sha256:1b68f0d54837c356e353efb04472bc0c9a60ae1c8178c9ce076b01d2930bcc5d
Status: Downloaded newer image for registry:latest
$ docker run -d -p5000:5000 registry
7768bed98a5e1916a820c84906e1f21cfc84888a934c140ad22e19cee5e2541d
Pull the “registry” image and run the container
You can now push/pull
images from this private
registry

How to get list of containers?

How to run a container?
Use “docker run OPTIONS <<image-tag>> CMD ARGS”
docker run fedora /bin/echo 'Hello world'
Command name
Image name
Command
argument
$ docker run fedora /bin/echo 'Hello world'
Hello world
$

How to run a container interactively?
$ docker run -t -i fedora /bin/bash
[root@00eef5289c91 /]# pwd
/
[root@00eef5289c91 /]# whoami
root
[root@00eef5289c91 /]# ls
bin boot dev etc home lib lib64 lost+found media mnt opt proc root run sbin srv
sys tmp usr var
[root@00eef5289c91 /]# cc
bash: cc: command not found
[root@00eef5289c91 /]# gcc
bash: gcc: command not found
[root@00eef5289c91 /]# java
bash: java: command not found
[root@00eef5289c91 /]# tar
bash: tar: command not found
[root@00eef5289c91 /]# exit
exit
$
docker run -t -i fedora /bin/bash
Create a terminal
to interact with
short for “—interactive"

Running a container - Totem?
$ hostname
ganesh
$ docker run -it alpine /bin/sh
/ # hostname
b4ebae46b156
/ # ps -a
PID USER TIME COMMAND
1 root 0:00 /bin/sh
6 root 0:00 ps -a
/ # exit
$ ps -a
PID TTY TIME CMD
15327 ttys001 0:00.02 login -pf gsamarthyam
15328 ttys001 0:00.27 -bash

How to run a container in the background?
$ docker run -d ubuntu /bin/sh -c "while true; do echo current date and time is: $(date); sleep
10; done"
9128bf57e03c3b32f0bf784a92332953996236d7e358a77c62c10bdec95fd5b9
$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS
PORTS NAMES
9128bf57e03c ubuntu "/bin/sh -c 'while tr" About a minute ago Up About a
minute lonely_einstein
$ docker logs 9128bf57e03c3b32f0bf784a92332953996236d7e358a77c62c10bdec95fd5b9
current date and time is: Fri Jul 22 15:42:49 IST 2016
// output elided
short for “—detach” and it runs
container in the background

How to expose a port?
$ docker run -d -p 80:80 nginx
host port (machine on
which this command is run)
mapped port -
nginx
"PortBindings": {
"80/tcp": [
{
"HostIp": "",
"HostPort": "80"
}
]
},
$ docker inspect 9128bf57e03c3b32f0bf784a92332953996236d7e358a77c62c10bdec95fd5b9

Using Nginx
Type http://localhost:80 in your browser window

How to expose a port?
$ docker run -d -p 80 --name minenginx nginx
host port (machine on which this command is run); since no explicit
mapped port number is provided, a random port number is assigned
$ docker inspect minenginx
"Ports": {
"443/tcp": null,
"80/tcp": [
{
"HostIp": "0.0.0.0",
"HostPort": "32770"
}
]
},
randomly assigned and mapped
port number (by docker)

How to expose all exposed ports?
$ docker run -d -P --name minenginx nginx
6b873116f198f4235e3eee1b2085e0312eaa0067217da614c62e2ce55a8c8d4e
$ docker port minenginx
443/tcp -> 0.0.0.0:32771
80/tcp -> 0.0.0.0:32772
-P publishes all exposed ports to random ports; in this case, ports
443 and 80 are respectively mapped to 32771 and 32772

How to attach to a running container?
$ docker run -d ubuntu /bin/sh -c "while true; do echo current date and time is: $
(date); sleep 10; done"
acc349675098a0133366076f2082db6171ee4a0cd2e1e45ada9a485684ea4c01
$ docker attach acc349675098a0133366076f2082db6171ee4a0cd2e1e45ada9a485684ea4c01
current date and time is: Mon Aug 1 10:30:13 IST 2016
current date and time is: Mon Aug 1 10:30:13 IST 2016
short for “—detach” and it runs
container in the background
The “attach” command attaches
to a running container

How to detach from a running container (without exiting)?
From docker documentation
# To detach the tty without exiting the shell,
# use the escape sequence Ctrl-p + Ctrl-q
# note: This will continue to exist in a stopped state once exited (see "docker ps -a")
$ docker run -it alpine /bin/sh
/ # echo "hello"
hello
/ # $ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS
NAMES
99d946d9b4e0 alpine "/bin/sh" 15 seconds ago Up 14 seconds
gloomy_mcclintock
$

How do I create an image from a running container?
Use “docker commit” command
$ docker run -d alpine echo "hello world"
9884347880f62f7c5d43702c3d701e3b87a49f9bdde5843380af1479f4dc0755
$ docker logs 9884347880f62f7c5d43702c3d701e3b87a49f9bdde5843380af1479f4dc0755
hello world
$ docker commit -m "my first image from container"
9884347880f62f7c5d43702c3d701e3b87a49f9bdde5843380af1479f4dc0755 myalpine:latest
sha256:b707ef35394c365bece70240213942e43da7f882107d30482ad6bec6b4bacfb7
$ docker images
REPOSITORY TAG IMAGE ID CREATED
SIZE
myalpine latest b707ef35394c 18 hours ago
4.799 MB
$ docker run -it b707ef35394c365bece70240213942e43da7f882107d30482ad6bec6b4bacfb7
hello world
$

Avoid “docker commit”
❖ Avoid creating docker images manually (e.g., using
“docker commit”); rather automate the image build
process (using Dockerﬁle and “docker build”)

How to get list of containers?
Use “docker ps” command
$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
3651758ff308 wordpress:latest "/entrypoint.sh apach" 2 days ago Up 2 days 0.0.0.0:8000->80/tcp mywordpress_wordpress_1
b95388054539 mysql:5.7 "docker-entrypoint.sh" 2 days ago Up 2 days 3306/tcp mywordpress_db_1

How do I see all the containers?
Use “docker ps -a” command
$ docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
2c378c6b84b1 fedora "/bin/echo 'Hello wor" 4 minutes ago Exited (0) 4 minutes ago grave_thompson
c4b2db95f268 hello-world "/hello" 5 minutes ago Exited (0) 5 minutes ago amazing_jones
2dcd9d0caf6f 777f9424d24d "/bin/bash" 42 minutes ago Exited (0) 42 minutes ago prickly_khorana
3651758ff308 wordpress:latest "/entrypoint.sh apach" 2 days ago Up 2 days 0.0.0.0:8000->80/tcp mywordpress_wordpress_1
b95388054539 mysql:5.7 "docker-entrypoint.sh" 2 days ago Up 2 days 3306/tcp mywordpress_db_1
4b984664f9aa golang:latest "go run myapp.go" 2 days ago Exited (1) 2 days ago mydocker_app_1
63cd7661a8ad hello-world "/hello" 2 days ago Exited (0) 2 days ago adoring_sammet
c191fbeae884 ubuntu "/bin/bash" 2 days ago Exited (0) 2 days ago clever_mcclintock
08e173332d46 docker/whalesay "cowsay Hello world" 2 days ago Exited (0) 2 days ago tender_joliot
6322b8204a5d 0f192147631d "/bin/bash" 9 days ago Exited (0) 9 days ago desperate_aryabhata
...

Explicitly remove exited containers
❖ Explicitly use --rm to remove the container from the ﬁle
system - otherwise, even if the container exits, it is not
cleaned up yet (and will hog memory).

How do I remove a container?
Use “docker rm” command
$ docker stop mywordpress_db_1
mywordpress_db_1
$ docker rm mywordpress_db_1
mywordpress_db_1
You have to ﬁrst stop a
container before trying
to remove it

How do I remove all the containers?
Use “docker stop $(docker ps -a -q)” and
“docker rm $(docker ps -a -q)” commands
$ docker stop $(docker ps -a -q)
00eef5289c91
8553eebfab94
696a04db91db
// rest of the output elided
$ docker rm $(docker ps -a -q)
00eef5289c91
8553eebfab94
696a04db91db
$ docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS
PORTS NAMES
Note how the output
shows no containers

Using nginx
$ docker run --name mynginx -P -d nginx
561e15ac1848cf481f89bb161c23dd644f176b8f142fe617947e06f095e0953f
$ docker ps
CONTAINER ID IMAGE COMMAND CREATED
STATUS PORTS NAMES
561e15ac1848 nginx "nginx -g 'daemon off" 18 hours ago
Up About a minute 0.0.0.0:32771->80/tcp, 0.0.0.0:32770->443/tcp mynginx
$ curl localhost:32771
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
body {
width: 35em;
margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif;
}
</style>
</head>
// rest of the output elided ...
Nginx exposes ports 80 and 443; -P maps them
randomly in the ports range 49153 and 65535

Using nginx
$ cat Dockerfile
FROM nginx:latest
MAINTAINER Ganesh Samarthyam
ADD ./index.html /usr/share/nginx/html/index.html
EXPOSE 80
$ cat index.html
<h1> welcome to Dockerizing apps! <h1>
$ docker build .
Sending build context to Docker daemon 3.072 kB
// output elided ...
Removing intermediate container b043a75a4e1c
Successfully built 1aae04309f8b
$ docker images
<none> <none> 1aae04309f8b 6 seconds ago 182.8 MB
$ docker run -p 80:80 -d 1aae04309f8b
984c179231188445289e70d854250e4e981b77a899208360db4466e73930be42
$ curl localhost:80
<h1> welcome to Dockerizing apps! <h1>
$
Type “localhost:80” in
the browser address bar

How do I run a C program?
$ docker pull gcc
Using default tag: latest
latest: Pulling from library/gcc
5c90d4a2d1a8: Already exists
ab30c63719b1: Already exists
c6072700a242: Already exists
abb742d515b4: Already exists
d32a4c04e369: Pull complete
276c31cf0a4c: Pull complete
a455d29f9189: Pull complete
dcfe5869552b: Pull complete
Digest: sha256:35256b5f4e4d5643c9631c92e3505154cd2ea666d2f83812b418cfdb1d5866e8
Status: Downloaded newer image for gcc:latest
$

$ docker pull ubuntu:latest
latest: Pulling from library/ubuntu
43db9dbdcb30: Pull complete
85a9cd1fcca2: Pull complete
c23af8496102: Pull complete
e88c36ca55d8: Pull complete
Digest: sha256:7ce82491d6e35d3aa7458a56e470a821baecee651fba76957111402591d20fc1
Status: Downloaded newer image for ubuntu:latest
$ docker run -i -t ubuntu /bin/bash
root@c191fbeae884:/# gcc
bash: gcc: command not found
root@c191fbeae884:/# apt-get update
root@c191fbeae884:/# apt-get install gcc
root@c191fbeae884:/# cat > hello.c
int main() { printf("hello worldn”); }
root@c191fbeae884:/# gcc -w hello.c
root@c191fbeae884:/# ./a.out
hello world
root@c191fbeae884:/#

$ cat Dockerfile
FROM gcc:latest
MAINTAINER Ganesh Samarthyam version: 0.1
COPY . /usr/src/mycapp
WORKDIR /usr/src/mycapp
RUN gcc -o first first.c
CMD ["./first"]
$ cat first.c
#include <stdio.h>
int main() { printf("hello worldn"); }
$ docker build . -t"mycapp:latest"
Step 1 : FROM gcc:latest
---> a0b516dc1799
// .. steps elided ...
Step 6 : CMD ./first
---> Using cache
---> f99e7f18fa42
Successfully built f99e7f18fa42
$ docker run -it mycapp
hello world

How do I run a Java program?
$ cat Dockerfile
FROM java:latest
COPY . /usr/src/
WORKDIR /usr/src/
RUN javac hello.java
CMD ["java", "hello"]
$ cat hello.java
class hello {
public static void main(String []args) {
System.out.println("hello world");
}
}
$ docker build . -t"myjavaapp:latest"
Step 1 : FROM java:latest
---> 264282a59a95
// intermediate steps elided
Successfully built 0d7a3a12ba9d
$ docker images
$ docker images
<none> <none> 7cfb4bdf47a7 About an hour ago 669.2 MB
$ docker run myjavaapp
hello world

Beware of “container sprawl”
❖ Application broken to run in “too many containers”can
be difﬁcult to deal with!
“Breaking deployments into more functional discrete
parts is smart, but that means we have MORE
PARTS to manage. There's an inﬂection point
between separation of concerns and sprawl.”
-- Rob Hirschfeld
(CEO of RackN and OpenStack Foundation board member)

Pop quiz
What happens when you execute this on the command-
line?
docker run debian /bin/sh
A. A prompt from the shell of created container will be thrown to you
B. A container is created and then exited immediately
C. A container is created and executes in the detached mode; you can
attach to it later using the container id
D. Docker CLI issues the error: Error response from daemon: No
command speciﬁed.

Pop quiz: answer
When you execute this command,
docker run debian /bin/sh
A container is created and then exited immediately.
$ docker ps -a
CONTAINER ID IMAGE COMMAND
CREATED STATUS PORTS NAMES
4c12998fd392 debian "/bin/bash"
6 seconds ago Exited (0) 5 seconds ago sick_panini

Pop quiz
What happens when you execute this on the command-
line?
docker run -itd debian
A. You get “Error response from daemon: No command speciﬁed.”
B. The created container runs in the detached mode
C. You get “unknown shorthand ﬂag: -itd”
D. A shell from the created container is returned to you

Pop quiz: answer
When you execute
docker run -itd debian
the created container runs in the detached mode!
$ docker ps
STATUS PORTS NAMES
a53779a74904 debian "/bin/bash" 2 minutes ago
Up 2 minutes agitated_aryabhata

Building images using Dockerfile

Different ways to create images
docker commit Build an image from a container
docker build
Create an image from a Dockerfile by executing the
build steps given in the file
docker import
Create a base image by importing from a tarball.
[import is mainly used for creating base-images; first
two options are widely used]

Dockerfile - key instructions
FROM
The base image for building the new docker image; provide “FROM scratch”
if it is a base image itself
MAINTAINER The author of the Dockerfile and the email
RUN Any OS command to build the image
CMD
Specify the command to be started when the container is run; can be
overridden by the explicit argument when providing docker run command
ADD Copies files or directories from the host to the container in the given path
EXPOSE Exposes the specified port to the host machine

How can I create an image from a Dockerfile?
Use docker build command
“Dockerfile” - its like Makefile for Docker
$ cat myimage/Dockerfile
FROM ubuntu
RUN echo "my first image" > /tmp/first.txt
$ docker build myimage
Step 1 : FROM ubuntu
---> ac526a356ca4
Step 2 : RUN echo "my first image" > /tmp/first.txt
---> Running in 18f62f47d2c8
---> 777f9424d24d
Removing intermediate container 18f62f47d2c8
Successfully built 777f9424d24d
$ docker images | grep 777f9424d24d
<none> <none> 777f9424d24d 4 minutes ago 125.2 MB
$ docker run -it 777f9424d24d
root@2dcd9d0caf6f:/# ls
bin boot core dev etc home lib lib64 media mnt opt proc root run sbin srv
sys tmp usr var
root@2dcd9d0caf6f:/# cat /tmp/first.txt
my first image
root@2dcd9d0caf6f:/# exit
exit
$

How to name/tag an image when building?
Use “docker build <<dirname>> -t"imagename:tag"” command
$ docker build myimage -t"myfirstimage:latest"
Step 1 : FROM ubuntu
---> ac526a356ca4
Step 2 : RUN echo "my first image" > /tmp/first.txt
---> Using cache
---> 777f9424d24d
Successfully built 777f9424d24d
$ docker images myfirstimage
myfirstimage latest 777f9424d24d 58 minutes ago 125.2 MB
$

Dockerfile for running a Java program
$ cat HiHello.java
import java.io.*;
import java.net.InetSocketAddress;
import com.sun.net.httpserver.*;
public class HiHello {
public static void main(String[] args) throws Exception {
HttpServer server = HttpServer.create(new InetSocketAddress(8080), 0);
server.createContext("/hi", (HttpExchange t) ->
{
try {
String response = "hellon";
t.sendResponseHeaders(200, response.length());
try(OutputStream os = t.getResponseBody()) {
os.write(response.getBytes());
}
} catch (IOException ioe) {
System.err.println("Error writing to outputstream: " + ioe);
System.exit(-1);
}
}
);
server.start();
}
}
$ curl localhost:8080/hi
hello

Dockerfile for running a Java program
$ cat Dockerfile
FROM java:latest
COPY HiHello.class /
EXPOSE 8080
ENTRYPOINT ["java"]
CMD ["HiHello"]
$ docker build .
Step 1 : FROM java:latest
---> 264282a59a95
// ... Successfully built 60a14f519720
$ docker run -d -p 8080:8080 60a14f519720
16f6d7eca560c96b995be9f0c6d68167930ab7501451a452818e04ce29ec177f
$ curl localhost:8080/hi
hello

Pop quiz
Which command do you use “to ﬁnd layers and their
sizes” in an image using Docker CLI?
A. Use “docker images -layers <<imageid>>” command
B. Use “docker layers <<imageid>> command
C. Use “docker history <<imageid>> command
D. There is no way you can ﬁnd layers and their sizes using Docker CLI
- you need to use external tools

Pop quiz: answer
To ﬁnd layers and their sizes in an image using Docker
CLI, use“docker history <<imageid>> command.
$ docker history google/cadvisor
IMAGE CREATED CREATED BY SIZE
COMMENT
106e303be3a4 2 weeks ago /bin/sh -c #(nop) ENTRYPOINT ["/usr/bin/cadvi 0 B
<missing> 2 weeks ago /bin/sh -c #(nop) EXPOSE 8080/tcp 0 B
<missing> 2 weeks ago /bin/sh -c #(nop) ADD file:1bde294f31142b3dee 25.87 MB
<missing> 2 weeks ago /bin/sh -c apk --no-cache add ca-certificates 17.13 MB
<missing> 2 weeks ago /bin/sh -c #(nop) ENV GLIBC_VERSION=2.23-r3 0 B
<missing> 2 weeks ago /bin/sh -c #(nop) MAINTAINER dengnan@google.c 0 B
<missing> 3 months ago /bin/sh -c #(nop) ADD file:852e9d0cb9d906535a 4.799 MB

Pop quiz
Which command do you use “recreate the Dockerfile
that was used to build that image” from a given image
id/tag using Docker CLI?
A. Use “docker images -dockerfile <<imageid>>” command
B. Use “docker build -reverse <<imageid>> command
C. Use “docker history --no-trunc --out:<filename> <<imageid>>
command
D. There is no way to recreate the Dockerfile that was used to build
that image from a given image id/tag using Docker CLI

Pop quiz: answer
There is NO way to recreate the Dockerfile that was used to build that
image from a given image id/tag using Docker CLI.
Think about Makefile: can you recreate the Makefile that was used to
build that executable file? No.
However, you can see the commands used to create the layers in the
image. Pass “—no-trunc” option to “docker history” command.
Example: “docker history --no-trunc google/cadvisor"
Try it now!

Docker volume commands
Command Description
docker volume create Create a volume
docker volume inspect
Display detailed information on one
or more volumes
docker volume ls List the available volumes
docker volume rm Remove one or more volumes

Commands for Docker volumes
$ docker volume create --name myvolume
myvolume
$ docker volume ls
local myvolume
$ docker volume inspect myvolume
[
{
"Name": "myvolume",
"Driver": "local",
"Mountpoint": "/var/lib/docker/volumes/myvolume/_data",
"Labels": {},
"Scope": "local"
}
]
$ docker volume rm myvolume
myvolume

How to persist data?
$ docker run -v /volumetesting --name="persistdata" alpine /bin/sh -c
"echo testing persistence with volumes > /volumetesting/textfile.txt”
$ docker run --volumes-from=persistdata alpine /bin/sh -c "cat /
volumetesting/textfile.txt"
testing persistence with volumes
Use -v option to “mount volumes”

How to get info on volumes?
$ docker volume ls
DRIVER VOLUME NAME
local 081bf425dd953c6b13f8e36f24540d191792e51dbd9c327eadae131ded5da432
local 3357f5522da19b47c3996db5e129b52d4be420ccec25d60d4473602cd25f473b
$ docker volume inspect
081bf425dd953c6b13f8e36f24540d191792e51dbd9c327eadae131ded5da432
[
{
"Name": "081bf425dd953c6b13f8e36f24540d191792e51dbd9c327eadae131ded5da432",
"Driver": "local",
"Mountpoint": "/var/lib/docker/volumes/
081bf425dd953c6b13f8e36f24540d191792e51dbd9c327eadae131ded5da432/_data",
"Labels": null,
"Scope": "local"
}
]
Use “docker volume ls and inspect” options

Removing volumes
$ docker volume rm 081bf425dd953c6b13f8e36f24540d191792e51dbd9c327eadae131ded5da432
081bf425dd953c6b13f8e36f24540d191792e51dbd9c327eadae131ded5da432
Use “docker volume rm” option

Removing containers with volumes
❖ When the container is removed, the volumes will not be
removed. If the volumes also need to be removed, you
have to use the -v option, as in: docker rm -v <<sha>>

Clean up volumes
❖ You can “clean up” the volumes if you aren't using them.
Use the command “docker volume rm $(docker volume
ls -q)“ to remove all the volumes.

Use Flocker (data volume manager)
source: https://clusterhq.com/assets/images/diagrams/diagram-1.jpg
See: https://clusterhq.com/ﬂocker/

Docker Machine
$ docker-machine create --driver=virtualbox myhost
Running pre-create checks...
(myhost) Default Boot2Docker ISO is out-of-date, downloading the latest release...
(myhost) Latest release for github.com/boot2docker/boot2docker is v1.12.2
(myhost) Downloading /Users/gsamarthyam/.docker/machine/cache/boot2docker.iso from https://github.com/
boot2docker/boot2docker/releases/download/v1.12.2/boot2docker.iso...
// ...
Setting Docker configuration on the remote daemon...
Checking connection to Docker...
Docker is up and running!
To see how to connect your Docker Client to the Docker Engine running on this virtual machine, run:
docker-machine env myhost
$ docker-machine env myhost
export DOCKER_TLS_VERIFY="1"
export DOCKER_HOST="tcp://192.168.99.100:2376"
export DOCKER_CERT_PATH="/Users/gsamarthyam/.docker/machine/machines/myhost"
export DOCKER_MACHINE_NAME="myhost"
# Run this command to configure your shell:
# eval $(docker-machine env myhost
$ docker-machine ls
NAME ACTIVE DRIVER STATE URL SWARM DOCKER ERRORS
myhost - virtualbox Running tcp://192.168.99.100:2376 v1.12.2
Create and manage machines running Docker (cloud or on your computer)

docker-compose commands
Command Description
docker-compose up (Re)build services
docker-compose kill Kill the containers
docker-compose logs Show the logs of the containers
docker-compose down
Stop and remove images, containers, volumes
and networks
docker-compose rm Remove stopped containers

Creating multiple Docker
containers
Step 1. Create a docker-compose.yml ﬁle (or docker-compose.yaml ﬁle)
Step 2. Execute “docker-compose up -d”
Step 3. Execute “docker-compose logs” from another shell (but from same dir)
Step 4. Execute “docker-compose down”

Docker voting app
Step 1. Download .zip or clone: https://github.com/docker/example-voting-app
Step 2. Unzip the ﬁle and go to that directory from your shell
Step 3. Type “docker-compose up -d”
Step 4. From another shell, go to the same directory & type “docker-compose logs”
Step 5. In browser address bar, type “http://localhost:5000"
Step 6. In browser address bar, type “http://localhost:5001"
Step 7. From the shell, in that directory, type “docker-compose down”

Getting the ip address of a container
$ docker inspect --format '{{ .NetworkSettings.IPAddress }}' fervent_sinoussi
172.17.0.6
$ docker attach fervent_sinoussi
root@856aed6a92f1:/# ip addr
// ...
92: eth0@if93: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group
default
link/ether 02:42:ac:11:00:06 brd ff:ff:ff:ff:ff:ff
inet 172.17.0.6/16 scope global eth0
valid_lft forever preferred_lft forever
inet6 fe80::42:acff:fe11:6/64 scope link
valid_lft forever preferred_lft forever
root@856aed6a92f1:/# cat /etc/hosts
// ...
172.17.0.6 856aed6a92f1
root@856aed6a92f1:/#
There are many ways to get the IP address of a
container:
1. Use the docker inspect command
2. Use ip addr command from the container’s shell
3. Use “cat /etc/hosts” and check the entry for the
container

How to get port mappings of a container?
$ docker run -d -p5000:5000 registry
c51b984b4d64a05e924c7677f20e8c5c386e8bb53f5de0369337d31f73a7cf7e
$ docker port
c51b984b4d64a05e924c7677f20e8c5c386e8bb53f5de0369337d31f73a7cf7e
5000/tcp -> 0.0.0.0:5000
$ docker run -P -d nginx
de6e17ededc8223c9a5ac9fee4f9493929a22a78fe88c60b643b545078c60648
$ docker port
de6e17ededc8223c9a5ac9fee4f9493929a22a78fe88c60b643b545078c60648
443/tcp -> 0.0.0.0:32768
80/tcp -> 0.0.0.0:32769
$ docker ps
STATUS PORTS NAMES
de6e17ededc8 nginx "nginx -g 'daemon off" 21 seconds
ago Up 20 seconds 0.0.0.0:32769->80/tcp, 0.0.0.0:32768->443/tcp
reverent_wright

Three kinds of networks
$ docker network ls
NETWORK ID NAME DRIVER SCOPE
a3bb9a40c8e3 bridge bridge local
399711fd0635 host host local
790ae8b43d9b none null local
Default, single-host driver

Docker network commands
Command Description
docker network connect Connect a container to a network
docker network create Create a network
docker network disconnect
Disconnect a container from a
network
docker network inspect
Display detailed information on one
or more networks
docker network ls List networks
docker network rm Remove one or more networks

Bridge network
$ docker network inspect bridge
[
{
"Name": "bridge",
"Id": "39457e56e7c0d172a239745e10ebf24f9e5046e9bc98f978f4e759f1f4e486c3",
"Scope": "local",
"Driver": "bridge",
"EnableIPv6": false,
"IPAM": {
"Driver": "default",
"Options": null,
"Config": [
{
"Subnet": "172.17.0.0/16",
"Gateway": "172.17.0.1"
}
]
},
"Internal": false,
"Containers": {
"19857aa228f7ba76fc10d1e992e9fe49a0d361b5daab3a0a2703267aab862c58": {
"Name": "furious_mcnulty",
"EndpointID": "e2a7423a9108fa7bb18ea9893e299e1bceb73fa13c3123c5b0d515790be477d3",
"MacAddress": "02:42:ac:11:00:03",
"IPv4Address": "172.17.0.3/16",
"IPv6Address": ""
},
"eaf4697b9989666e0c79cce6dc03697c8226aea37157d97bce1d08e250fb3c36": {
"Name": "cadvisor",
"EndpointID": "f907c7510aaf7196e6419733b64da689330948ca0f3c88bd4dd41258a4503e42",
"MacAddress": "02:42:ac:11:00:02",
"IPv4Address": "172.17.0.2/16",
"IPv6Address": ""
}
},
"Options": {
"com.docker.network.bridge.default_bridge": "true",
"com.docker.network.bridge.enable_icc": "true",
"com.docker.network.bridge.enable_ip_masquerade": "true",
"com.docker.network.bridge.host_binding_ipv4": "0.0.0.0",
"com.docker.network.bridge.name": "docker0",
"com.docker.network.driver.mtu": "1500"
},
"Labels": {}
}
]
By default, containers are
added to the bridge network.
You can see the containers in
bridge network here

Pop quiz
You are creating a new container with this command:
docker run -d --name myubuntu ubuntu /bin/sh -c "while true; do echo current date and
time is: $(date); sleep 10; done”
Which network is the “myubuntu” container attached
to?
A. Bridge
B. Overlay
C. Custom
D. None

Pop quiz: answer
Bridge network. By default, a newly created container is attached to the
bridge network (unless a different network is speciﬁed, for example, using
the “—network” option with the docker run command).
$ docker network inspect bridge
[
{
"Name": “bridge",
// ...
"Containers": {
"04579b88a74c981ae854261dffc7ab17328c28bb6fafec0f9c1e9431e77b3b27": {
"Name": "myubuntu",
"EndpointID":
"8a0e7a2559eac35eb60a90e85554679de276bd1ba39ff3a4083301d08e9ee384",
"MacAddress": "02:42:ac:11:00:03",
"IPv4Address": "172.17.0.3/16",
"IPv6Address": ""
},
// ...
},
// ...
}
]

Orchestration
Docker swarm provides
“clustering capabilities”, i.e.,
be able to treat group of
Docker engines into a single
virtual Docker engine

Docker Swarm
“swap, plug, and play”

Docker Swarm
$ docker swarm init
Swarm initialized: current node (81snul7czu9pg42h3qnm2v5hr) is now a manager.
To add a worker to this swarm, run the following command:
docker swarm join --token
SWMTKN-1-2tn8fic07uivk29ith095me3r6cro7bkrfnbtv6va3qvf6urew-6olc37m9ljymly3fcb6rig2nu
192.168.65.2:2377
To add a manager to this swarm, run 'docker swarm join-token manager' and follow the
instructions.

Clustering for Docker
“batteries included but swappable”

Docker workbench for security
docker run -it --net host --pid host --cap-add audit_control
-v /var/lib:/var/lib
-v /var/run/docker.sock:/var/run/docker.sock
-v /usr/lib/systemd:/usr/lib/systemd
-v /etc:/etc --label docker_bench_security
docker/docker-bench-security
git clone https://github.com/docker/docker-bench-security.git
cd docker-bench-security
sh docker-bench-security.sh
git clone https://github.com/docker/docker-bench-security.git
cd docker-bench-security
docker-compose run --rm docker-bench-security
OR
OR
Source: https://github.com/docker/docker-bench-security

$ sh docker-bench-security.sh
# ------------------------------------------------------------------------------
# Docker Bench for Security v1.1.0
#
# Docker, Inc. (c) 2015-
#
# Checks for dozens of common best-practices around deploying Docker containers in production.
# Inspired by the CIS Docker 1.11 Benchmark:
# https://benchmarks.cisecurity.org/downloads/show-single/index.cfm?file=docker16.110
# ------------------------------------------------------------------------------
[WARN] Some tests might require root to run
[INFO] 1 - Host Configuration
[WARN] 1.1 - Create a separate partition for containers
[PASS] 1.2 - Use an updated Linux Kernel
[WARN] 1.4 - Remove all non-essential services from the host - Network
[WARN] * Host listening on: 7 ports
[PASS] 1.5 - Keep Docker up to date
[INFO] * Using 1.12.1 which is current as of 2016-08-16
[INFO] * Check with your operating system vendor for support and security maintenance for docker
[INFO] 1.6 - Only allow trusted users to control Docker daemon
[WARN] 1.7 - Failed to inspect: auditctl command not found.
[INFO] 1.8 - Audit Docker files and directories - /var/lib/docker
[INFO] * Directory not found
[INFO] 1.9 - Audit Docker files and directories - /etc/docker
[INFO] * Directory not found
...
[INFO] 2 - Docker Daemon Configuration
[WARN] 2.1 - Restrict network traffic between containers
[PASS] 2.2 - Set the logging level
[PASS] 2.3 - Allow Docker to make changes to iptables
[PASS] 2.4 - Do not use insecure registries
[WARN] 2.5 - Do not use the aufs storage driver
[INFO] 2.6 - Configure TLS authentication for Docker daemon
[INFO] * Docker daemon not listening on TCP
[INFO] 2.7 - Set default ulimit as appropriate
[INFO] * Default ulimit doesn't appear to be set
[WARN] 2.8 - Enable user namespace support
[PASS] 2.9 - Confirm default cgroup usage
[PASS] 2.10 - Do not change base device size until needed
[WARN] 2.11 - Use authorization plugin
[WARN] 2.12 - Configure centralized and remote logging
[WARN] 2.13 - Disable operations on legacy registry (v1)
...

❖ Use the free Docker Workbench For Security (https://
github.com/docker/docker-bench-security) to check for
violations of security best practices

Stats for all running containers
Use “docker stats” command
$ docker stats
Displays resource utilisation (cpu,
memory, etc) details; automatically
updated when details change

Stats for a specific Docker
Use “docker stats <<CONTAINTER_ID>>” command
$ docker stats sleepy_wescoff
CONTAINER CPU % MEM USAGE / LIMIT MEM % NET I/O BLOCK I/O PIDS
sleepy_wescoff 0.00% 1.031 MiB / 4 MiB 25.78% 648 B / 648 B 0 B / 0 B 1

Printing containers names in stat
$ docker stats $(docker ps --format={{.Names}})

Monitoring Docker
Use the free cAdvisor tool
(https://github.com/google/cadvisor)
Now open localhost:8080 in your browser
docker run --volume=/:/rootfs:ro --volume=/var/run:/var/run:rw —volume=/
sys:/sys:ro --volume=/var/lib/docker/:/var/lib/docker:ro --publish=8080:8080
--detach=true --name=cadvisor google/cadvisor:latest

Monitoring Docker
localhost:8080

Monitoring Docker
❖ datadog (https://www.datadoghq.com/)
❖ sysdig (http://www.sysdig.org/)
❖ prometheus (https://prometheus.io/)

How do debug on a running container?
$ docker ps -a
STATUS PORTS NAMES
9128bf57e03c ubuntu "/bin/sh -c 'while tr" 24 minutes ago Up
24 minutes lonely_einstein
$ docker exec -ti lonely_einstein /bin/bash
root@9128bf57e03c:/#
Use “docker exec” command

Can I use GUI instead of command-line?
Use “kitematic” (https://github.com/docker/kitematic)

Different ways to access Docker
Command-Line
Interface (CLI)
Graphical User
Interface (Kitematic)
Representational State
Transfer (REST) API

Crazy stuff: Docker in Docker!!
Use “docker run --privileged -d docker:dind"
“docker:dind” is the official “Docker in Docker base image”
See: https://github.com/jpetazzo/dind

Docker *completely* replaces
VMs

Docker is *completely* portable
There are limitations to portability with Docker (depending on
what you mean by “portable”).
For example, you can run a Windows Docker container only on
Windows and run a Linux Docker container only on Linux
(and not vice versa).
Build once, run anywhere - but conditions apply!

“Management says we need
Docker, so let’s use it”

Docker commands
attach Attach to a running container
build Build an image from a Dockerfile
commit Create a new image from a container's changes
cp Copy files/folders between a container and the local filesystem
create Create a new container
deploy Create and update a stack from a Distributed Application Bundle (DAB)
diff Inspect changes on a container's filesystem
events Get real time events from the server
exec Run a command in a running container
export Export a container's filesystem as a tar archive
history Show the history of an image
images List images
import Import the contents from a tarball to create a filesystem image
info Display system-wide information
inspect Return low-level information on a container, image or task
kill Kill one or more running container
load Load an image from a tar archive or STDIN
login Log in to a Docker registry.
logout Log out from a Docker registry.
logs Fetch the logs of a container
network Manage Docker networks
node Manage Docker Swarm nodes
pause Pause all processes within one or more containers
plugin Manage Docker plugins

Docker commands
port List port mappings or a specific mapping for the container
ps List containers
pull Pull an image or a repository from a registry
push Push an image or a repository to a registry
rename Rename a container
restart Restart a container
rm Remove one or more containers
rmi Remove one or more images
run Run a command in a new container
save Save one or more images to a tar archive (streamed to STDOUT by default)
search Search the Docker Hub for images
service Manage Docker services
stack Manage Docker stacks
start Start one or more stopped containers
stats Display a live stream of container(s) resource usage statistics
stop Stop one or more running containers
swarm Manage Docker Swarm
tag Tag an image into a repository
top Display the running processes of a container
unpause Unpause all processes within one or more containers
update Update configuration of one or more containers
version Show the Docker version information
volume Manage Docker volumes
wait Block until a container stops, then print its exit code

Source: http://zeroturnaround.com/wp-content/uploads/2016/03/Docker-cheat-sheet-by-RebelLabs.png

Relevant URLs
❖ Detailed list of resources: https://github.com/hangyan/
docker-resources
❖ Self-learning courses: https://training.docker.com/
❖ Detailed documentation: https://docs.docker.com/
❖ Detailed tutorial (presentation): http://docker.training
❖ SE-Radio Episode 217: James Turnbull on Docker
❖ Docker related presentations in parleys.com
❖ Blog on Docker resource utilisation

DOCKER: UP & RUNNING
➤ Covers how to develop, test,
debug, ship, scale, and
support with Docker from
DevOps perspective
➤ We liked the useful tips;
examples:
➤ “Maximize robustness with fast
startup and graceful shutdown.”
➤ “Explicitly declare and isolate
dependencies.”
➤ “Strictly separate build and run
stages.”
http://amzn.com/1491917571
“Docker: Up & Running”, Karl Matthias, Sean P. Kane, O'Reilly Media; 1 edition (July 3, 2015)

THE DOCKER BOOK
➤ Interesting sub-title:
“Containerization is the new
virtualization”.
➤ From James Turnbull (CTO at
Kickstarter and Advisor at
Docker)
➤ Useful to get comfortable with
core concepts of Docker
➤ Useful for developers,
operations staﬀ (and DevOps),
and SysAdmins
➤ Supporting website: http://
dockerbook.com/http://www.amazon.in/dp/B00LRROTI4
The Docker Book, James Turnbull, Amazon Digital South Asia Services, July 2014

DOCKER COOKBOOK
➤ Contents written in recipe
format (Problem, Solution,
Discussion)
➤ Useful because we can look for
solutions to the problems that
we face when using Docker
➤ What we like: it covers topics
that are not covered well in
other books including
Kubernetes, Docker ecosystem
tools, monitoring Docker, and
application use cases (CI, CD)
http://amzn.com/149191971X
“Docker Cookbook”, Sébastien Goasguen, O'Reilly Media, 2015

DOCKER IN ACTION
➤ Wide coverage from basics to
advanced topics like managing
massive clusters
➤ Book organised into three parts:
➤ Keeping a tidy computer
➤ Packaging software for distribution
➤ Multi-container and multi-host
environments
➤ The third part is more
interesting for us because it is
not covered well in other books
➤ Covers Docker Compose, Machine
and Swarm
Docker in Action, Jeff Nickoloff, Manning Publications, 2016

USING DOCKER
➤ Book organised into three
parts:
➤ Background and Basics
➤ The Software Lifecycle with Docker
➤ Tools and Techniques
➤ Useful example: Walks you
through the steps to develop
and deploy web applications
with Docker
➤ Though the book touches
upon basics, it covers more
advanced topics
Using Docker: Developing and Deploying Software with Containers, Adrian Mouat, O'Reilly Media, 2016

Upcoming bootcamps
AngularJS (22nd Oct)
Modern Software Architecture (5th Nov)
SOLID Principles (19th Nov)

Meetups
h"p://www.meetup.com/JavaScript-Meetup-Bangalore/
h"p://www.meetup.com/Container-Developers-Meetup-Bangalore/
h"p://www.meetup.com/So>ware-Cra>smanship-Bangalore-Meetup/
h"p://www.meetup.com/Core-Java-Meetup-Bangalore/
h"p://www.meetup.com/Technical-Writers-Meetup-Bangalore/
h"p://www.meetup.com/CloudOps-Meetup-Bangalore/
h"p://www.meetup.com/Bangalore-SDN-IoT-NetworkVirtualizaHon-Enthusiasts/
h"p://www.meetup.com/So>wareArchitectsBangalore/

ganesh@codeops.tech @GSamarthyam
www.codeops.tech slideshare.net/sgganesh
+91 98801 64463 bit.ly/ganeshsg

Image credits
❖ https://pbs.twimg.com/media/CH-ISJGUwAAt8hQ.png
❖ http://patg.net/assets/container_vs_vm.jpg
❖ http://static1.businessinsider.com/image/525e9c7669bedd9c3015dc60-1190-625/the-10-funniest-dilbert-comic-strips-about-idiot-bosses.jpg
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