Docker Containers Crash Course
Docker Crash Course
As Hypervisor is slow to boot and use a lot of resources and needs full installation
the Container Technology not that old we used to use LXC – openVZ extra
but what a cool about Docker is it really lightweight with awesome images build and we can ship many services in one machine
it comes into two parts [DockerClient, DockerServer]
and today i will write the best quick intro i could tell
1 – Introduction [how it will work]
docker run the process inside the container and when it has done it EXIT the container ( by EXIT I mean it STOP the container )
docker has official images [distros] called saved in ( registry ) there is public registry also you can have a private registry, example hub.docker.com
every container you run get id example 915c72318028
2- installation
you can get docker to install from https://get.docker.com
wget https://get.docker.com -O docker_setup.sh
we did download the sh install filer remember to user CAPITAL -O
we run the docker setup via root account
to verify Docker Installation use
$ docker version Version: 1.11.1 API version: 1.23 Go version: go1.5.4 Git commit: 5604cbe Built: Tue Apr 26 23:30:23 2016 OS/Arch: linux/amd64 Server: Version: 1.11.1 API version: 1.23 Go version: go1.5.4 Git commit: 5604cbe Built: Tue Apr 26 23:30:23 2016 OS/Arch: linux/amd64
as you can there is 2 versions for the client and server
3- Basic Usage
to be able to run container First you have to decide what image you want to use
so lets pickup ubuntu for example
so we can search the public hub to find ubuntu by
compiler@ubuntu:~/docker$ sudo docker search ubuntu NAME DESCRIPTION STARS OFFICIAL AUTOMATED ubuntu Ubuntu is a Debian-based Linux operating s... 3999 [OK] ubuntu-upstart Upstart is an event-based replacement for ... 63 [OK] rastasheep/ubuntu-sshd Dockerized SSH service, built on top of of... 28 [OK] torusware/speedus-ubuntu Always updated official Ubuntu docker imag... 26 [OK] ubuntu-debootstrap debootstrap --variant=minbase --components... 24 [OK] ioft/armhf-ubuntu [ABR] Ubuntu Docker images for the ARMv7(a... 12 [OK] nickistre/ubuntu-lamp LAMP server on Ubuntu 7 [OK]
there is a list of Ubuntu images but the most important is the OFFICIAL images ( the one we can trust )
FYI: you and other people can make and upload images easily
so let’s RUN our first ubuntu container via docker
for the first time docker will pull images from the hub and save it locally in your machine for faster boot 😀
to list the current images
$ docker images
REPOSITORY TAG IMAGE ID CREATED SIZE ubuntu latest 2fa927b5cdd3 2 days ago 122 MB nginx latest b1fcb97bc5f6 5 days ago 182.8 MB hello-world latest 94df4f0ce8a4 4 weeks ago 967 B
compiler@ubuntu:~/docker$ docker run ubuntu compiler@ubuntu:~/docker$ echo $? 0 compiler@ubuntu:~/docker$
and here we go.
yes as you see EXACTLY the command passed successfully,
so where is the container!
you can list running containers via docker ps
compiler@ubuntu:~/docker$ sudo docker ps CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES compiler@ubuntu:~/docker$
as you can see it not listed because ps is for running containers only!
the answer for the next question, simple yes your container finished work and stopped as we mentioned in the introduction
Docker will keep your container running as long as you keep it busy ( this is the cool thing about Docker and Resource Save )
so let’s list all containers even the stopped one
compiler@ubuntu:~/docker$ docker ps -a CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 915c72318028 ubuntu "/bin/bash" 14 minutes ago Exited (0) 14 minutes ago elegant_snyder compiler@ubuntu:~/docker$
the status of the container is Exited (0)
so next time we need run container with a command to see it working
compiler@ubuntu:~/docker$ sudo docker run ubuntu id uid=0(root) gid=0(root) groups=0(root) compiler@ubuntu:~/docker$ compiler@ubuntu:~/docker$ sudo docker run ubuntu uname -a Linux 4a27417f50b9 3.13.0-86-generic #131-Ubuntu SMP Thu May 12 23:33:13 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux compiler@ubuntu:~/docker$
and this means we run 2 containers and the status of them stopped
as you can see the container started in less than a second
jump in container shell
but this time we will add 2 parameters to run -i -t
-i, –interactive Keep STDIN open even if not attached
-t, –tty Allocate a pseudo-TTY
this both to keep us connected to a container
compiler@ubuntu:~$ sudo docker run -it ubuntu /bin/bash root@75907b371305:/# hostname 75907b371305 root@75907b371305:/# id uid=0(root) gid=0(root) groups=0(root) root@75907b371305:/# uptime 01:03:48 up 1 day, 9:13, 0 users, load average: 0.00, 0.01, 0.05 root@75907b371305:/#
docker in detached mode
compiler@ubuntu:~/docker$ sudo docker run -itd ubuntu /bin/bash 96d3c78ab0f8927693e448444445781b45e61796b914990ef4acd0986aca096d compiler@ubuntu:~/docker$ docker ps CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 96d3c78ab0f8 ubuntu "/bin/bash" 2 seconds ago Up 2 seconds stupefied_morse
no we have the container up and running
using port forward with docker in detached mode
docker come with awesome port mapping, for example, we want to run nginx container and by
image default it listens to 80,443
compiler@ubuntu:~/docker$ docker run -d -P nginx 1c0c6bc0c34fc6648a426b6c9d58eb079c86471c1bea521a720b3f3204f76059 compiler@ubuntu:~/docker$
compiler@ubuntu:~/docker$ sudo docker ps CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 1c0c6bc0c34f nginx "nginx -g 'daemon off" About a minute ago Up About a minute 0.0.0.0:32775->80/tcp, 0.0.0.0:32774->443/tcp gigantic_noether
there is 2 port forwards here
0.0.0.0:32775->80/tcp, 0.0.0.0:32774->443/tcp
localhost:32775 to nginx container:80
localhost:32774 to nginx container:443/tcp
4- Building Docker Images
building a docker image is like create an ( OS Template ) for reuse, you don’t have to setup all your dependencies each time you decide to run container, you build image once and you use it as mass production.
Docker Images
first, we need to understand how is images looks like
images
compiler@ubuntu:~/docker$ sudo docker images REPOSITORY TAG IMAGE ID CREATED SIZE ubuntu latest 2fa927b5cdd3 2 days ago 122 MB nginx latest b1fcb97bc5f6 5 days ago 182.8 MB
images come with repository and tag
each repository can have many apps
for example:
privterepo/webserver
privterepo/db
privterepo/logs
and each app could have a tag name example
privterepo/webserver:2.5.1
privterepo/webserver:2.6.1
Docker Commit ( save container changes as a template )
so we need to install some packages inside one of our containers let’s say we want to install python Django
and all our app dependencies once you did finish with installing your packages
let’s save the status of this container as image
first, we need 3 things
1 – Container ID
2- Registry Name ( you can write anything you want depends if you will upload it or not )
3- modification name
4- Tag name ( Version )
let’s assume we build a container for development and we installed our needed libs
we will use the container id to commit it docker commit 505815e27433 private/app:1.0
compiler@ubuntu:~/docker$ docker commit 505815e27433 private/app:1.0 sha256:3c7881fe969f5be91f8b766910a7d5dea94db7900b1d31dd2ded259d73fec2b6 compiler@ubuntu:~/docker$ docker images REPOSITORY TAG IMAGE ID CREATED SIZE privte/app 1.0 3c7881fe969f 3 seconds ago 129.3 MB nginx latest b1fcb97bc5f6 5 days ago 182.8 MB
as you can see in our images there is a new one with id: 3c7881fe969f
also, you can create an image without specifying a version
$ docker commit 505815e27433 private/app
and an image will be versioned as the latest
private/app latest b2f06fe9a07d 2 seconds ago 129.3 MB
so we can use our new image to build as many as containers on it
keep in mind you can make multi commits for the same modification you made in a container
running Docker container from a self-made image
docker run -it private/app:1.0 /bin/bash
or use the latest version ( the default tag name )
docker run -it private/app /bin/bash
Destroy all containers
docker rm -f `docker ps -a|awk '{print $1}'|grep -v CONTAINER`
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