How to install Docker?

In this post we are going to learn about how to install docker in ubuntu 14.04 LTS.Before getting stared , I would like to say all of the items here are mainly from docker documentation. And those who want to know what process will be for windows or Mac, here is the basic difference which we need to know before installation.

docker-concept

That means, you need additionally a VM(usually virtual box) on top of docker if it is not Linux. The virtual box VM will work as boot2Docker. We sill follow the things needed for Linux only. And all of the command here are in command line.

docker needs minimum Kernel version 3.10. To check kernel version :
```
  uname -r  
```

kernel-info-vm

kernel-info

As both cases, they are 3.10+, we are set to go. There are two ways to install , I am including both ways.

Primary Installation:

I have tested in Ubuntu 14.04, 18.04, 19.10 : Preferable method for error free installation.
Check APT work with HTTP : If you dont have https enable for APT, just download certificate
```
  sudo apt-get install apt-transport-https ca-certificates
```

Add public key for server to download :

  sudo apt-key adv --keyserver hkp://p80.pool.sks-keyservers.net:80 --recv-keys 58118E89F3A912897C070ADBF76221572C52609D

Adding docker repository source : Go to this folder (/etc/apt/sources.list.d) and find a file docker.list. If you find, open this as root and delete any entry if you have. If you don’t have this file, create this file.
```
  sudo touch  docker.list 
```

Now , edit this file

    sudo gedit docker.list

and add this following repository name & save it

    deb https://apt.dockerproject.org/repo ubuntu-trusty main

Optional : If you want to use multiple architecture(x64 & x86) , you may specify like this

    deb [arch=amd64,i386] https://apt.dockerproject.org/repo ubuntu-trusty main

This will enable x86 & x64. I am only using x64.

Note : If you go that repository you will see following folders

    debian-jessie/                              
    debian-stretch/                             
    debian-wheezy/                              
    ubuntu-precise/                             
    ubuntu-trusty/                              
    ubuntu-utopic/                              
    ubuntu-vivid/                              
    ubuntu-wily/

If you Ubuntu version is not 14 (trusty), then you may use other destination. On this part is different then other Ubuntu versions.Now, Update APT

    sudo apt-get update

verify APT is pulling from right repository
```
  sudo apt-cache policy docker-engine 
```

docker-engine

To check, if APT is not getting from old repo,
```
  sudo apt-get purge lxc-docker 
```

docker-lxc

Get Linux Image Extra kernel, To do that

  sudo apt-get install linux-image-extra-$(uname -r)

It will update the current extra image kernel. If you are in latest , you don’t need. to run this. You might see something like this.

docker-lxc

We need apparmor, for application security. So, if you dont have apparmor, you can install
```
  sudo apt-get install apparmor
```
By default apparmor used to present in ubuntu 14. So, you may see like this.

apparmor

We need both generic and required kernel. So, Update APT and

  sudo apt-get install -y linux-image-generic-lts-trusty

Reboot PC .

Finally we are in installation step!

  sudo apt-get -y install docker-engine

Validate Installations :

Let’s test installation.

    sudo docker run hello-world

docker-hello-world

Optional Steps :

If you want to run docker as service , run this as service
```
  sudo service docker start
```
If you want to add an user for docker , (I am putting my name)
```
  sudo usermod -aG docker shantonu
```
Reboot PC(or log out) . Now you can use docker without root rights. If you try
```
  docker run hello-world 
```

docker-hello-world2

Finally Installation is complete.

Alternative Installation :

tested in Ubuntu Mate 14, based on LTS
Step 1 : Install CURL (skip if you already have)
```
  sudo apt-get install -y curl
```

Step 2 : Download & install docker

    curl -fsSL https://get.docker.com/ | sh

It will prompt for root credential , you need to provide that.

Optional step : Adding an user (i am adding my username, so that I do not need root rights each time I use docker) :
```
  sudo usermod -aG docker shantonu
```
And now, try hello world : (add sudo if you haven’t add user)
```
  docker run hello-world
```

docker-hello-world2

And, installation is complete.

Configure Docker for development

it will allow to use docker complete for development. These are mainly permission or admin related things.
Using swap memory if you have less Ram : Edit grub as root etc/default/grub
```
  sudo gedit /etc/default/grub
```

And add this line

  GRUB_CMDLINE_LINUX="cgroup_enable=memory swapaccount=1"

grab

Now , save & update grub
```
  sudo update-grub
```

UFW firewall entry :

To know the status of you PC of UFW, type this (you may avoid verbose)
```
  sudo ufw status verbose
```

fw-init

I am not using after by default , so inactive.if you are using firewall(you should) , Change DEFAULT_FORWARD_POLICY, DROP to ACCEPT
```
  sudo gedit /etc/default/ufw
```

fw-setup

Save & close file. And, now Reload UFT
```
  sudo ufw reload
```
Add Docker port for incoming container request.
```
  sudo ufw allow 2375/tcp
```

fw-setup-done

Configure DNS :

We need to add DNS entry for our Docker outgoing calls. Usually /etc/resolv.conf shortcut used to have local host entry.
```
  gedit /etc/resolv.conf 
```

dns

So, Docker access this & when try to use, it cant as it is used by our Ubuntu. So, Docker try using default Google Public DNS servers 8.8.8.8 8.8.4.4 . We need to make this DNS entry to our Local host IP address. So, know your IP address by ifconfig and use that. In my case it is 192.168.0.19. So,
```
  sudo gedit /etc/default/docker
```

dns-config

And add your local address. Now, as you can see we can add multiple DNS address, so, if your PC connected to multiple network (wifi, lan etc) , you should add those address so that each time you change network, you dont need to add dns.
Save & close file.
restart docker
```
  sudo restart docker
```

We are ready to use docker in Ubuntu.

Thanks.. :)