Austin - Container Days - Docker 101

© 2015 Rancher Labs, Inc.© 2016 Rancher Labs, Inc .
Container Days: Docker
101
October 13

© 2015 Rancher Labs, Inc.© 2016 Rancher Labs, Inc .2
Bill Maxwell
Principal Eng. @ Rancher Labs
@cloudnautique
bill@rancher.com
#ranchermeetup

Agenda
Docker Intro
Container Basics
Building
Storage
Networking

STOP
Docker Install Time
https://docs.docker.com/engine/installation/

VM vs Containers

Note: Containers ≠ microservices
…but containers are a good way of packaging and delivering microservices
[PS: you can still use VMs]

Our Goal: A Production Container Service
7
Develop Build Containerize Test Deploy/Upgrade Operate

Runtimes
runC
lxc/lxd
openVZ
rkt
docker

Docker Containers
Mantra: Build once, run anywhere
• A clean and portable runtime environment for your application (or service)
• No worries about missing dependencies, packages, etc during subsequent
deployments
• Automate testing, integration, and packaging…anything you can script
• Reduce concerns around compatibility on different platforms (either your own,
or your customers
• Instant replay and reset of image snapshots
Docker containers are helping organizations achieve agility and efficiency

© 2015 Rancher Labs, Inc.© 2016 Rancher Labs, Inc .10
Docker is helping organizations
achieve agility and efficiency
1
2
Improve the speed and reliability of
software development organizations
Operate that software reliably
at a reasonable cost

Isolation Mechanisms
• Cgroups – Metering and Limiting
• Namespaces
• Pid
• User
• Net
• Mnt
• Ipc
• User
• Layered Copy On Write Filesystems

Docker flow
Docker
file
Push
Build Registry
Pull
Host
Run

Building Images
FROM alpine
RUN apk add --update bash
mysql-client
openssl
vim &&
rm -rf /var/cache/apk/*
CMD /bin/echo hello
Dockerfile
Base Image
Install Software
Default Command

Anatomy of an Image
Base Image
Layer 1
Layer 2
Layer 3

What Happens?
• Base image is pulled from
registry.
• A container is created and the
next command is executed.
• The result is committed to a
layer in the image.

Demo Images/Building

Building Images Cont.
FROM alpine
RUN apk add --update bash
mysql-client
openssl
vim &&
ADD ./script.sh /
CMD /bin/echo hello
Add a file from the local build context

Exercise
Build a Docker image from Alpine that executes:
script.sh:
#!/bin/bash
echo “hello world”

Exercise Solution
#!/bin/bash
echo “hello world”
FROM alpine
RUN apk add --update bash &&
ADD ./script.sh /
CMD /script.sh
script.sh
Dockerfile $ ls ./
Dockerfile script.sh

Demo Docker Push

Notes on Tags
• By default Docker uses
:latest tag.
• Docker checks for image
locally, then checks
registry.
• Always run a versioned tag
in a production system

Docker Run
docker run –d nginx
docker run –it debian bash
docker logs <container id>
See the stdout/stderr from a container:
docker exec –it <container id> /bin/bash
Jump inside a container with a shell:

Exercise
Run the container from previous exercise in both interactive and
Detached mode.
Enter the detached container with docker exec

Docker Run From a Filesystem perspective
Base Image
Layer 1
Layer 2
Layer 3
Container 1
Filesystem
Container 2
Filesystem

Exercise
Run 2 containers from the same image and see that changes
on the local file system do not impact the other.

Docker volumes
Base Image
Layer 1
Layer 2
Layer 3
By Default layered file systems. Keep mapping
table in memory.
AUFS doesn’t do Hard Links… good luck running Tox

Docker volumes
Base Image
Layer 1
Layer 2
Layer 3
Use a VOLUME
Dockerfile:
Volume /path
Runtime:
-v /path
/var/lib/docker
Filesystem
Running
Container
/path

Volume Plugins
Docker plugin binaries that
can mount storage and
attach to containers.

Host Bind Mounts
Directly mount any path on the host file system inside the
container.
docker run –it –v /data:/data alpine sh

Volumes From
Share volumes between containers!
Data
Container
Container 1 Container 2

Volume Exercises
1. Docker volume ls
2. docker run --name some-mysql -e MYSQL_ROOT_PASSWORD=my-secret-pw -d mysql
3. Docker volume ls
4. Docker volume create –name mysql-data
5. docker run --name some-mysql-named-volume -e MYSQL_ROOT_PASSWORD=my-
secret-pw –d –v mysql-data:/var/lib/mysql mysql
6. mkdir ./data
7. docker run --name some-mysql-host-volume -e MYSQL_ROOT_PASSWORD=my-secret-
pw –d –v $(pwd)/data:/var/lib/mysql mysql
8. Create a volume container

Docker networking
• Containers run in their own
network namespace.
• Port mapping to host interface
for outside accessiblity.
Host
Interface
Docker Bridge
Container

Demo Networking Modes
None
Host

Linking
Creates Directional Link
Creates DNS / Host
lookup
Creates ENV variables
Container 1 Container 2

Exposing Ports
Allows traffic from
outside of the Docker
bridged network.
Host
Interface
Docker Bridge
Container
Outside world

Demo
Linking
Setting hostname
Setting host:ip mapping

Exercise
Create Mysql Container and link a mysql client container to it.
Run nginx container and reach port

Pulling it all together
Lets run:
https://github.com/realpython/orchestrating-docker

Advanced Topics
Namespace sharing!
Security Considerations
Daemon settings

Thank you!
Questions?
Contact: mpaluru@rancher.com

Austin - Container Days - Docker 101

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