Slide 1
Slide 1 text
Introduction to containers and Docker
By Santiago Lizardo
Slide 2
Slide 2 text
2
2
whoami
Santiago Lizardo
• Manager
• Software engineer at heart
• +4 years at SolarWinds
We want YOU! https://solarwinds.jobs/gbr/jobs/
• Some years playing with Docker...
Slide 3
Slide 3 text
Introduction to containers and Docker
Agenda
• History
• Using Docker containers
Demo: Hello world, Ubuntu, MySQL, Apache
• Building Docker images
Demo: Creation of “solarwinds/webapp” image containining Apache + PHP + MySQL connector
• Multi-container apps with Docker
Demo: MySQL + “solarwinds/webapp”
Bonus content
• Docker under the hood
Slide 4
Slide 4 text
History
4
Slide 5
Slide 5 text
5
5
In the beginning there was only darkness…
Slide 6
Slide 6 text
6
In the beginning there was only darkness…
Slide 7
Slide 7 text
7
In the beginning there was only darkness…
Slide 8
Slide 8 text
8
8
Slide 9
Slide 9 text
9
9
Slide 10
Slide 10 text
10
10
Slide 11
Slide 11 text
11
11
Slide 12
Slide 12 text
12
12
Slide 13
Slide 13 text
13
13
PHP 5.6
PHP 7.2
Slide 14
Slide 14 text
14
14
PHP 5.6
PHP 7.2
Slide 15
Slide 15 text
15
System diversity matrix
Slide 16
Slide 16 text
16
Transportation metaphor matrix
Slide 17
Slide 17 text
17
Invention of the shipping container
Slide 18
Slide 18 text
18
Transportation metaphor applied to software
distribution
Slide 19
Slide 19 text
19
Docker history
Slide 20
Slide 20 text
20
Docker alternatives
Slide 21
Slide 21 text
Docker popularity stats
Since it started in March 2013...
Slide 22
Slide 22 text
22
Docker and Kubernetes trends
https://trends.google.com/trends/explore?date=today%205-y&q=docker,kubernetes,xen,virtualbox,vmware
Slide 23
Slide 23 text
23
Docker elevator pitch
Docker is an open platform for developing,
shipping, and running applications.
Docker allows you to package an application with
all of its dependencies into a standardized unit for
software development.
Slide 24
Slide 24 text
Docker containers
24
Slide 25
Slide 25 text
25
Slide 26
Slide 26 text
26
What is a container?
• Standardized packaging for software and
dependencies
• Isolate apps from each other
• Share the same OS kernel
• Works for all major Linux distributions
• Containers native to Windows Server 2016
Slide 27
Slide 27 text
27
Docker vs virtualization
• Lighter than virtual machines
Size of docker images are very small
Containers have less startup time
More efficiency without the OS overhead
We can run more docker containers than VMs
on a same box
•Deploying and scaling is relatively easy
Slide 28
Slide 28 text
28
What is a container?
Slide 29
Slide 29 text
29
Worries
Slide 30
Slide 30 text
30
Key benefits of Docker containers
Devs
Predictability: Build once, run
anywhere
o Consistent between environments
Portable: Bundled dependencies
Isolation: No application clashing
Scriptable
Efficiency:
o Setup dev environments in seconds
Testability
o Images are snapshots
o Automation
o Integration
o Packaing
Continuous integration
Ops
Flexibility: Configure once, run
anything
Consistency: Identical environments
o Test, staging, production, …
Efficiency:
o Better resources (disk, CPU, RAM) utilisation –
compared to VMs-
o Faster restarts and deployments
Easy to scale
Slide 31
Slide 31 text
31
Basic terminology
Image
The basis of a Docker container. The content at rest
Container
The image when it's running. The standard unit for app service
Engine
The software that executes commands for containers. Networking and volumes are part of
the Engine. Can be clustered together.
Registry
Stores, distributes and manages Docker images
Control panel
Management plane for container and cluster orchestration
Slide 32
Slide 32 text
32
Docker volumes
Slide 33
Slide 33 text
33
Docker volumes
• Volumes mount a directory on the host into the container at a specific
location
$ docker volume create world_volume
world_volume
$ docker run -d -v world_volume :/world busybox ls /world
• Can be used to share (and persist) data between containers
• Directory persists after the container is deleted
• Unless you explicitly delete it
• Can be created in a Dockerfile or via CLI
Slide 34
Slide 34 text
34
34
Basic information
Version
Info
Stats
Help (help run)
Running
Run
• Interactive mode
• Detached
• Port mapping
• Volume mapping
Inspecting
Logs
Port
Inspect (--format )
Top
container ls
Image ls (-all)
Stopping
stop (SIGTERM + SIGKILL)
kill (SIGKILL)
container rm
Slide 35
Slide 35 text
Docker images
35
Slide 36
Slide 36 text
36
Base images and commits
• Connect to the box
• Make changes
• Commit
docker pull nginx
docker run --name nginx-template-base -p 8080:80 -e TERM=xterm -d nginx
docker exec -it CONTAINER_ID bash
$ apt-get install nano
$ exit
docker commit CONTAINER_ID nginx-template
- Better use Dockerfile
Slide 37
Slide 37 text
37
Dockerfile
• Instructions on how to build
a Docker image
• Similar to native commands
• It can be version controlled
Slide 38
Slide 38 text
38
Dockerfile (windows)
Slide 39
Slide 39 text
39
Docker layers
Slide 40
Slide 40 text
40
Docker layers
Slide 41
Slide 41 text
41
Copy on Write
• Super efficient:
Sub second instantiation times for containers
New container can take <1 Mb of space
• Containers appears to be a copy of the original image
• But, it is really just a link to the original shared image
• If someone writes a change to the file system, a copy
of the affected file/directory is “copied up”
Slide 42
Slide 42 text
42
Dockerfile commands
•FROM — set base image
•RUN — execute command in container
•ENV — set environment variable
•WORKDIR — set working directory
•COPY – Copies files from host to image
•VOLUME — create mount-point for a volume
•CMD — set executable for container
Slide 43
Slide 43 text
43
43
Registries
Pull
Push
Building
Build –t .
Tagging
Tag sourcetag targettag
Removing
image rm ![]()
Slide 44
Slide 44 text
Demo:
Slide 45
Slide 45 text
Multi-container apps with Docker
45
Slide 46
Slide 46 text
46
Multi-container apps
Without compose
• Build and run one container at a time
• Manually connect containers together
• Must be careful with dependencies and
startup order
With compose
• Define multi container app in compose.yml
file
• Single command to deploy entire app
• Handles container dependencies
• Works with Docker Swarm, Networking,
Volumes, Universal Control Plane
Slide 47
Slide 47 text
47
Multi-container apps
Slide 48
Slide 48 text
Docker under the hood
48
Slide 49
Slide 49 text
49
49
Technology behind Docker
• Linux x86-64
• Go language
• Client - Server (deamon) architecture
• Union file systems (UnionFS: AUFS, btrfs, vfs etc)
• Namespaces (pid, net, ipc, mnt, uts)
• Control Groups (cgroups)
• Container format (libcontainer)
Slide 50
Slide 50 text
50
50
•High level: a lightweight VM
•Own process space
•Own network interface
•Can run stuff as root
•Can have its own /sbin/init (different from host)
<>
•Low level: chroot on steroids
•Can also not have its own /sbin/init
•Container = isolated processes
•Share kernel with host
<>
Slide 51
Slide 51 text
51
Technology behind Docker
• Control groups
Key component of Linux Containers
Implement resource accounting and limiting
Ensure each container gets its fair share of memory, CPU, disk I/O
Cgroup ensures a single container cannot bring the system down by
exhausting resources
• Union file systems
Layered file system so you can have a read only part and a write part,
and merge those together
Docker images made up with are layers
Slide 52
Slide 52 text
52
Technology behind Docker
• Namespaces
It helps to create isolated workspace for each process
Namespaces are created every time you run a container
• SELinux
SELinux provides secure separation of containers by applying SELinux
policy and label
Slide 53
Slide 53 text
Q&A