In continuation of my  previous session on :”11. DevOps: How to Launch a container as a daemon ?”, in this session I would like to demonstrate the exercises on:

“How to build docker images using dockerfile ?:”

These images are basic operating environments, such as ubuntu.
We found these while doing the other lab exercises.
The docker images can craft advanced application stacks for the enterprise and cloud IT environments.
Currently let us craft an image manually by launching a container from a base image.
A best practices is, we can build an automated approach of crafting the images using Dockerfile.
The dockerfile is a a text-based build script which contains special instructions in a sequence for building the correct and the relevant images from the base images.

Please note; we will explore all these combinations in different sessions.

Now, let us understand this automated approach from the below steps:
1. The sequential instructions inside Dockerfile can include selecting the base image as 1st statement.
2. And in the later statements; installing the required application, adding the configuration and the data files, and automatically running the services as well as exposing those services to the external world.

This way the dockerfile based automated build approach has simplified the image building process.

It also offers a great deal of flexibility in organizing the build instructions and in visualizing the complete build process, while running the script instructions.

The Docker Engine tightly integrates this build process with the help of the docker ‘build’ subcommand.

This process involes the below steps:
1. Let us imagine; in the client server scenario of Docker, the Docker server (or daemon) is responsible towards complete build process.
2. And the Docker command-line interface is responsible for transferring the build context, including transferring Dockerfile to the daemon.
Now, let us list our existing images as below, in continuation of previous exercise:
=============>
vskumar@ubuntu:~$
vskumar@ubuntu:~$ sudo docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
docker-exercise/ubuntu-wgetinstall latest e34304119838 7 days ago 169MB
<none> <none> fc7e4564eb92 7 days ago 169MB
hello-world latest f2a91732366c 12 days ago 1.85kB
ubuntu 16.04 20c44cd7596f 2 weeks ago 123MB
ubuntu latest 20c44cd7596f 2 weeks ago 123MB
busybox latest 6ad733544a63 4 weeks ago 1.13MB
busybox 1.24 47bcc53f74dc 20 months ago 1.11MB
vskumar@ubuntu:~$
====================>
Now,  let us create a simple container from the ubuntu base image.
To create it, we can create ‘dockerfile’ without extension using vi in the current pwd.

Please note we do not have vim utility in this Ubuntu base image.
=================>
vskumar@ubuntu:~$ pwd
/home/vskumar
vskumar@ubuntu:~$ vi dockerfile
============>
Now, let us cat the dockerfile as below:
=============>
vskumar@ubuntu:~$ ls -l
total 48
drwxr-xr-x 3 vskumar vskumar 4096 Nov 24 23:32 Desktop
-rw-rw-r– 1 vskumar vskumar 86 Dec 3 04:29 dockerfile
drwxr-xr-x 2 vskumar vskumar 4096 Nov 22 21:23 Documents
drwxr-xr-x 2 vskumar vskumar 4096 Nov 25 06:33 Downloads
-rw-r–r– 1 vskumar vskumar 8980 Nov 22 21:03 examples.desktop
drwxr-xr-x 2 vskumar vskumar 4096 Nov 22 21:23 Music
drwxr-xr-x 2 vskumar vskumar 4096 Nov 25 06:02 Pictures
drwxr-xr-x 2 vskumar vskumar 4096 Nov 22 21:23 Public
drwxr-xr-x 2 vskumar vskumar 4096 Nov 22 21:23 Templates
drwxr-xr-x 2 vskumar vskumar 4096 Nov 22 21:23 Videos
vskumar@ubuntu:~$
vskumar@ubuntu:~$ cat dockerfile
FROM ubuntu
CMD [“echo”, “This is done by vskumar for a lab practice of dockerfile”]
vskumar@ubuntu:~$
================>
From the above dockerfile contents:
1st line FROM ubuntu – denotes it is using the buntu as the base image to create the container.
2nd line: CMD [“echo”, “This is done by vskumar for a lab practice of dockerfile”]
denotes using CMD echo command is executed to print the message “This is done by vskumar for a lab practice of dockerfile”.
Now let us run this file through the below command:
$ sudo docker build .
We can see the output as below:
===============>
vskumar@ubuntu:~$ sudo docker build .
Sending build context to Docker daemon 112MB
Step 1/2 : FROM ubuntu
—> 20c44cd7596f
Step 2/2 : CMD [“echo”, “This is done by vskumar for a lab practice of dockerfile”]
—> Running in 1de59a4799fa
Removing intermediate container 1de59a4799fa
—> 8de083612fef
Successfully built 8de083612fef
vskumar@ubuntu:~$
===================>
Now, let us list the images:
==================>
vskumar@ubuntu:~$
vskumar@ubuntu:~$ sudo docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
<none> <none> 8de083612fef About a minute ago 123MB
docker-exercise/ubuntu-wgetinstall latest e34304119838 7 days ago 169MB
<none> <none> fc7e4564eb92 7 days ago 169MB
hello-world latest f2a91732366c 12 days ago 1.85kB
ubuntu 16.04 20c44cd7596f 2 weeks ago 123MB
ubuntu latest 20c44cd7596f 2 weeks ago 123MB
busybox latest 6ad733544a63 4 weeks ago 1.13MB
busybox 1.24 47bcc53f74dc 20 months ago 1.11MB
vskumar@ubuntu:~$
==========================>
We can see Imgae id: 8de083612fef is created just now.
Look into that line there is no tag given.
Now let us tag it as below:
$ sudo docker tag 8de083612fef ubuntu-testbox1
================>
vskumar@ubuntu:~$
vskumar@ubuntu:~$ sudo docker tag 8de083612fef ubuntu-testbox1
vskumar@ubuntu:~$ sudo docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
ubuntu-testbox1 latest 8de083612fef 4 minutes ago 123MB
docker-exercise/ubuntu-wgetinstall latest e34304119838 7 days ago 169MB
<none> <none> fc7e4564eb92 7 days ago 169MB
hello-world latest f2a91732366c 12 days ago 1.85kB
ubuntu 16.04 20c44cd7596f 2 weeks ago 123MB
ubuntu latest 20c44cd7596f 2 weeks ago 123MB
busybox latest 6ad733544a63 4 weeks ago 1.13MB
busybox 1.24 47bcc53f74dc 20 months ago 1.11MB
vskumar@ubuntu:~$
====================>
Now, let us do some housekeeping on these containers.
Let us list the containers using ps -a command
====================>
vskumar@ubuntu:~$ sudo docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
0fe495fc93ed ubuntu “/bin/bash -c ‘while…” 8 hours ago Exited (137) 4 hours ago hungry_engelbart
10ffea6140f9 ubuntu “bash” 7 days ago Exited (0) 7 days ago quizzical_lalande
b2a79f8d2fe6 ubuntu “/bin/bash -c ‘while…” 7 days ago Exited (255) 7 days ago goofy_borg
155f4b0764b1 ubuntu:16.04 “/bin/bash” 7 days ago Exited (0) 7 days ago zen_volhard
vskumar@ubuntu:~$
=====================>
I want to remove all of them. We can recreate with the dockerfile as an exercise.
$ Sudo docker containers prune
=======================================>
vskumar@ubuntu:~$ sudo docker ps -aq
0fe495fc93ed
10ffea6140f9
b2a79f8d2fe6
155f4b0764b1
vskumar@ubuntu:~$ sudo docker container prune
WARNING! This will remove all stopped containers.
Are you sure you want to continue? [y/N] y
Deleted Containers:
0fe495fc93edee3aaadc7fc0fbf21997f0ca3cde4d7e563aa8c61352a43957dd
10ffea6140f9c93b37bad2f9d159ad53aa121c0de69a9d145f07cc12f9591324
b2a79f8d2fe65453fce19f00d7adf03ed6dcced69ae68fba94ad0c416545263e
155f4b0764b16f1c8776a101cced6ea95c55eeabe69aeab8520cbe925bedc456

Total reclaimed space: 186B
vskumar@ubuntu:~$ sudo docker ps -aq
vskumar@ubuntu:~$
============== so now there are no containers =========>
Let us build the container.
Before building let us check the available images:
==================>
vskumar@ubuntu:~$ sudo docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
ubuntu-testbox1 latest 8de083612fef 24 minutes ago 123MB
docker-exercise/ubuntu-wgetinstall latest e34304119838 7 days ago 169MB
<none> <none> fc7e4564eb92 7 days ago 169MB
hello-world latest f2a91732366c 12 days ago 1.85kB
ubuntu 16.04 20c44cd7596f 2 weeks ago 123MB
ubuntu latest 20c44cd7596f 2 weeks ago 123MB
busybox latest 6ad733544a63 4 weeks ago 1.13MB
busybox 1.24 47bcc53f74dc 20 months ago 1.11MB
vskumar@ubuntu:~$
====================>
Let us remove some more images also.
We need to use the below commands:
=========== Let us try one image removal =========>
vskumar@ubuntu:~$ sudo docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
ubuntu-testbox1 latest 8de083612fef 33 minutes ago 123MB
docker-exercise/ubuntu-wgetinstall latest e34304119838 7 days ago 169MB
<none> <none> fc7e4564eb92 7 days ago 169MB
hello-world latest f2a91732366c 12 days ago 1.85kB
ubuntu 16.04 20c44cd7596f 2 weeks ago 123MB
ubuntu latest 20c44cd7596f 2 weeks ago 123MB
busybox latest 6ad733544a63 4 weeks ago 1.13MB
busybox 1.24 47bcc53f74dc 20 months ago 1.11MB
vskumar@ubuntu:~$ sudo docker rmi image 47bcc53f74dc
Untagged: busybox:1.24
Untagged: busybox@sha256:8ea3273d79b47a8b6d018be398c17590a4b5ec604515f416c5b797db9dde3ad8
Deleted: sha256:47bcc53f74dc94b1920f0b34f6036096526296767650f223433fe65c35f149eb
Deleted: sha256:f6075681a244e9df4ab126bce921292673c9f37f71b20f6be1dd3bb99b4fdd72
Deleted: sha256:1834950e52ce4d5a88a1bbd131c537f4d0e56d10ff0dd69e66be3b7dfa9df7e6
Error: No such image: image
vskumar@ubuntu:~$
=================================>
So, by using :
sudo docker rmi image [image id], we can remove the image.

Now, further continuation of our dockerfile exercise;
We can create a container from ubuntu base image and install vim package on it with the help of dockerfile.
To do this we need to have following dockerfile script.
——————>
FROM ubuntu
RUN apt-get update
RUN apt-get -y install vim
CMD [“echo”, “This is done by vskumar for a lab demo on dockerfile”]
—————–>
Before doing it, let me do some housekeeping.
I have removed the below image:
==================>
vskumar@ubuntu:~$
vskumar@ubuntu:~$ sudo docker rmi image 6ad733544a63
Untagged: busybox:latest
Untagged: busybox@sha256:bbc3a03235220b170ba48a157dd097dd1379299370e1ed99ce976df0355d24f0
Deleted: sha256:6ad733544a6317992a6fac4eb19fe1df577d4dec7529efec28a5bd0edad0fd30
Deleted: sha256:0271b8eebde3fa9a6126b1f2335e170f902731ab4942f9f1914e77016540c7bb
Error: No such image: image
=====================>
See the current status:
===================>
vskumar@ubuntu:~$ ls
Desktop dockerfile Documents Downloads examples.desktop Music Pictures Public Templates Videos
vskumar@ubuntu:~$ sudo docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
ubuntu-testbox1 latest 8de083612fef About an hour ago 123MB
docker-exercise/ubuntu-wgetinstall latest e34304119838 7 days ago 169MB
<none> <none> fc7e4564eb92 7 days ago 169MB
hello-world latest f2a91732366c 12 days ago 1.85kB
ubuntu 16.04 20c44cd7596f 2 weeks ago 123MB
vskumar@ubuntu:~$
======================>
Now let me update the dockerfile through vi and cat that file:
====================>
vskumar@ubuntu:~$
vskumar@ubuntu:~$ pwd
/home/vskumar
vskumar@ubuntu:~$ vi dockerfile
vskumar@ubuntu:~$ cat dockerfile
FROM ubuntu
RUN apt-get update
RUN apt-get -y install vim
CMD [“echo”, “This is done by vskumar for a lab practice of dockerfile”]
vskumar@ubuntu:~$
====================>
Now let me run the below command:
$ sudo docker build -t ubuntu-vmbox .
This time; I have added the tag name as ‘ ubuntu-vmbox’.
We need to understand; there are below tasks it involves:
1. Updating the ubuntu libraries – it takes some time by displaying lot of output.
2. Installing vim utility. — This also takes some time.
3. Displaying the message.
We can see this large size output:
=========== Update the packages and install the vim in a conatiner ==========>
vskumar@ubuntu:~$ pwd
/home/vskumar
vskumar@ubuntu:~$ sudo docker build -t ubuntu-vmbox .
Sending build context to Docker daemon 112MB
Step 1/4 : FROM ubuntu
latest: Pulling from library/ubuntu
Digest: sha256:7c67a2206d3c04703e5c23518707bdd4916c057562dd51c74b99b2ba26af0f79
Status: Downloaded newer image for ubuntu:latest
—> 20c44cd7596f
Step 2/4 : RUN apt-get update
—> Running in df81eaef9437
Get:1 http://archive.ubuntu.com/ubuntu xenial InRelease [247 kB]
Get:2 http://security.ubuntu.com/ubuntu xenial-security InRelease [102 kB]
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Get:7 http://archive.ubuntu.com/ubuntu xenial/main amd64 Packages [1558 kB]
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Get:21 http://security.ubuntu.com/ubuntu xenial-security/multiverse amd64 Packages [3479 B]
Fetched 24.6 MB in 2min 5s (196 kB/s)
Reading package lists…
Removing intermediate container df81eaef9437
—> 13cd766374bc
Step 3/4 : RUN apt-get -y install vim
—> Running in d37783a8cb7d
Reading package lists…
Building dependency tree…
Reading state information…
The following additional packages will be installed:
file libexpat1 libgpm2 libmagic1 libmpdec2 libpython3.5 libpython3.5-minimal
libpython3.5-stdlib libsqlite3-0 libssl1.0.0 mime-support vim-common
vim-runtime
Suggested packages:
gpm ctags vim-doc vim-scripts vim-gnome-py2 | vim-gtk-py2 | vim-gtk3-py2
| vim-athena-py2 | vim-nox-py2
The following NEW packages will be installed:
file libexpat1 libgpm2 libmagic1 libmpdec2 libpython3.5 libpython3.5-minimal
libpython3.5-stdlib libsqlite3-0 libssl1.0.0 mime-support vim vim-common
vim-runtime
0 upgraded, 14 newly installed, 0 to remove and 2 not upgraded.
Need to get 12.2 MB of archives.
After this operation, 58.3 MB of additional disk space will be used.
Get:1 http://archive.ubuntu.com/ubuntu xenial/main amd64 libgpm2 amd64 1.20.4-6.1 [16.5 kB]
Get:2 http://archive.ubuntu.com/ubuntu xenial/main amd64 libmagic1 amd64 1:5.25-2ubuntu1 [216 kB]
Get:3 http://archive.ubuntu.com/ubuntu xenial/main amd64 file amd64 1:5.25-2ubuntu1 [21.2 kB]
Get:4 http://archive.ubuntu.com/ubuntu xenial-updates/main amd64 libexpat1 amd64 2.1.0-7ubuntu0.16.04.3 [71.2 kB]
Get:5 http://archive.ubuntu.com/ubuntu xenial/main amd64 libmpdec2 amd64 2.4.2-1 [82.6 kB]
Get:6 http://archive.ubuntu.com/ubuntu xenial-updates/main amd64 libssl1.0.0 amd64 1.0.2g-1ubuntu4.9 [1085 kB]
Get:7 http://archive.ubuntu.com/ubuntu xenial-updates/main amd64 libpython3.5-minimal amd64 3.5.2-2ubuntu0~16.04.4 [523 kB]
Get:8 http://archive.ubuntu.com/ubuntu xenial/main amd64 mime-support all 3.59ubuntu1 [31.0 kB]
Get:9 http://archive.ubuntu.com/ubuntu xenial/main amd64 libsqlite3-0 amd64 3.11.0-1ubuntu1 [396 kB]
Get:10 http://archive.ubuntu.com/ubuntu xenial-updates/main amd64 libpython3.5-stdlib amd64 3.5.2-2ubuntu0~16.04.4 [2132 kB]
Get:11 http://archive.ubuntu.com/ubuntu xenial-updates/main amd64 vim-common amd64 2:7.4.1689-3ubuntu1.2 [103 kB]
Get:12 http://archive.ubuntu.com/ubuntu xenial-updates/main amd64 libpython3.5 amd64 3.5.2-2ubuntu0~16.04.4 [1360 kB]
Get:13 http://archive.ubuntu.com/ubuntu xenial-updates/main amd64 vim-runtime all 2:7.4.1689-3ubuntu1.2 [5164 kB]
Get:14 http://archive.ubuntu.com/ubuntu xenial-updates/main amd64 vim amd64 2:7.4.1689-3ubuntu1.2 [1036 kB]
debconf: delaying package configuration, since apt-utils is not installed
Fetched 12.2 MB in 12s (949 kB/s)
Selecting previously unselected package libgpm2:amd64.
(Reading database … 4768 files and directories currently installed.)
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Adding ‘diversion of /usr/share/vim/vim74/doc/help.txt to /usr/share/vim/vim74/doc/help.txt.vim-tiny by vim-runtime’
Adding ‘diversion of /usr/share/vim/vim74/doc/tags to /usr/share/vim/vim74/doc/tags.vim-tiny by vim-runtime’
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Unpacking vim (2:7.4.1689-3ubuntu1.2) …
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Setting up libgpm2:amd64 (1.20.4-6.1) …
Setting up libmagic1:amd64 (1:5.25-2ubuntu1) …
Setting up file (1:5.25-2ubuntu1) …
Setting up libexpat1:amd64 (2.1.0-7ubuntu0.16.04.3) …
Setting up libmpdec2:amd64 (2.4.2-1) …
Setting up libssl1.0.0:amd64 (1.0.2g-1ubuntu4.9) …
debconf: unable to initialize frontend: Dialog
debconf: (TERM is not set, so the dialog frontend is not usable.)
debconf: falling back to frontend: Readline
debconf: unable to initialize frontend: Readline
debconf: (Can’t locate Term/ReadLine.pm in @INC (you may need to install the Term::ReadLine module) (@INC contains: /etc/perl /usr/local/lib/x86_64-linux-gnu/perl/5.22.1 /usr/local/share/perl/5.22.1 /usr/lib/x86_64-linux-gnu/perl5/5.22 /usr/share/perl5 /usr/lib/x86_64-linux-gnu/perl/5.22 /usr/share/perl/5.22 /usr/local/lib/site_perl /usr/lib/x86_64-linux-gnu/perl-base .) at /usr/share/perl5/Debconf/FrontEnd/Readline.pm line 7.)
debconf: falling back to frontend: Teletype
Setting up libpython3.5-minimal:amd64 (3.5.2-2ubuntu0~16.04.4) …
Setting up mime-support (3.59ubuntu1) …
Setting up libsqlite3-0:amd64 (3.11.0-1ubuntu1) …
Setting up libpython3.5-stdlib:amd64 (3.5.2-2ubuntu0~16.04.4) …
Setting up vim-common (2:7.4.1689-3ubuntu1.2) …
Setting up libpython3.5:amd64 (3.5.2-2ubuntu0~16.04.4) …
Setting up vim-runtime (2:7.4.1689-3ubuntu1.2) …
Setting up vim (2:7.4.1689-3ubuntu1.2) …
update-alternatives: using /usr/bin/vim.basic to provide /usr/bin/vim (vim) in auto mode
update-alternatives: using /usr/bin/vim.basic to provide /usr/bin/vimdiff (vimdiff) in auto mode
update-alternatives: using /usr/bin/vim.basic to provide /usr/bin/rvim (rvim) in auto mode
update-alternatives: using /usr/bin/vim.basic to provide /usr/bin/rview (rview) in auto mode
update-alternatives: using /usr/bin/vim.basic to provide /usr/bin/vi (vi) in auto mode
update-alternatives: using /usr/bin/vim.basic to provide /usr/bin/view (view) in auto mode
update-alternatives: using /usr/bin/vim.basic to provide /usr/bin/ex (ex) in auto mode
update-alternatives: using /usr/bin/vim.basic to provide /usr/bin/editor (editor) in auto mode
Processing triggers for libc-bin (2.23-0ubuntu9) …
Removing intermediate container d37783a8cb7d
—> c07c6f2d2c65
Step 4/4 : CMD [“echo”, “This is done by vskumar for a lab practice of dockerfile”]
—> Running in f7e85f87b578
Removing intermediate container f7e85f87b578
—> f6675f4738b7
Successfully built f6675f4738b7
Successfully tagged ubuntu-vmbox:latest
vskumar@ubuntu:~$
=== Finally you can see the ‘ubuntu-vmbox’ tagged conatiner ======>
We can see the latest image from the below images:
===== Current images list =====>
vskumar@ubuntu:~$ sudo docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
ubuntu-vmbox latest f6675f4738b7 3 minutes ago 220MB
ubuntu-testbox1 latest 8de083612fef About an hour ago 123MB
docker-exercise/ubuntu-wgetinstall latest e34304119838 7 days ago 169MB
<none> <none> fc7e4564eb92 7 days ago 169MB
hello-world latest f2a91732366c 12 days ago 1.85kB
ubuntu 16.04 20c44cd7596f 2 weeks ago 123MB
ubuntu latest 20c44cd7596f 2 weeks ago 123MB
vskumar@ubuntu:~$
=======================>
Now, I want to work with this newly created container. Please recollect my blog “https://vskumar.blog/2017/11/29/6-devops-how-to-work-with-interactive-docker-containers/”.
As we did practice in it; we can use the below command to work with this new container:

sudo docker run -i -t ubuntu-vmbox /bin/bash
I want to test the vim is working on it. See the below output:
==================>
vskumar@ubuntu:~$ sudo docker run -i -t ubuntu-vmbox /bin/bash

root@1169bb1285cf:/#
root@1169bb1285cf:/# pwd
/
root@1169bb1285cf:/# ls
bin boot dev etc home lib lib64 media mnt opt proc root run sbin srv sys tmp usr var
root@1169bb1285cf:/# vim test1
===== I have created the file with vim successfully ====>
Now let me use cat command and see its output:

================>
root@1169bb1285cf:/#
root@1169bb1285cf:/# ls
bin boot dev etc home lib lib64 media mnt opt proc root run sbin srv sys test1 tmp usr var
root@1169bb1285cf:/# cat test1
testing this vim box……
root@1169bb1285cf:/#
=================>

So, in this exercise we have updated the ubuntu libraries and installed vim utility.
And tested the container for vim usage by using interactive mode.

=========== Now let me exit and check the list of images =====>
root@1169bb1285cf:/#
root@1169bb1285cf:/# exit
exit
vskumar@ubuntu:~$ sudo docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
ubuntu-vmbox latest f6675f4738b7 13 minutes ago 220MB
ubuntu-testbox1 latest 8de083612fef About an hour ago 123MB
docker-exercise/ubuntu-wgetinstall latest e34304119838 7 days ago 169MB
<none> <none> fc7e4564eb92 7 days ago 169MB
hello-world latest f2a91732366c 12 days ago 1.85kB
ubuntu 16.04 20c44cd7596f 2 weeks ago 123MB
ubuntu latest 20c44cd7596f 2 weeks ago 123MB
vskumar@ubuntu:~$
=============================>
So, the new container ‘ubuntu-vmbox’ is existing.

Now, I want to remove some images:
sudo docker rmi 20c44cd7596f
================>
vskumar@ubuntu:~$ sudo docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
ubuntu-vmbox latest f6675f4738b7 18 minutes ago 220MB
ubuntu-testbox1 latest 8de083612fef About an hour ago 123MB
docker-exercise/ubuntu-wgetinstall latest e34304119838 7 days ago 169MB
<none> <none> fc7e4564eb92 7 days ago 169MB
hello-world latest f2a91732366c 12 days ago 1.85kB
ubuntu 16.04 20c44cd7596f 2 weeks ago 123MB
ubuntu latest 20c44cd7596f 2 weeks ago 123MB
vskumar@ubuntu:~$ sudo docker rmi 20c44cd7596f
Error response from daemon: conflict: unable to delete 20c44cd7596f (cannot be forced) – image has dependent child images
vskumar@ubuntu:~$
== Please note the last image was the base to build the top tow containers ===>
Hence it has the child and parent relationship.
First we need to remove the child images and later the parent need to be removed.
=== You can see the removal of child one and one more image=====>
vskumar@ubuntu:~$ sudo docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
ubuntu-vmbox latest f6675f4738b7 20 minutes ago 220MB
ubuntu-testbox1 latest 8de083612fef 2 hours ago 123MB
docker-exercise/ubuntu-wgetinstall latest e34304119838 7 days ago 169MB
<none> <none> fc7e4564eb92 7 days ago 169MB
hello-world latest f2a91732366c 12 days ago 1.85kB
ubuntu 16.04 20c44cd7596f 2 weeks ago 123MB
ubuntu latest 20c44cd7596f 2 weeks ago 123MB
vskumar@ubuntu:~$ sudo docker rmi 8de083612fef
Untagged: ubuntu-testbox1:latest
Deleted: sha256:8de083612fefbf9723913748f7db4aba4154b17adc500d011f44df356736f06c
vskumar@ubuntu:~$ sudo docker rmi e34304119838
Untagged: docker-exercise/ubuntu-wgetinstall:latest
Deleted: sha256:e34304119838d79da60e12776529106c350b1972cd517648e8ab90311fad7b1a
vskumar@ubuntu:~$ sudo docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
ubuntu-vmbox latest f6675f4738b7 21 minutes ago 220MB
<none> <none> fc7e4564eb92 7 days ago 169MB
hello-world latest f2a91732366c 12 days ago 1.85kB
ubuntu 16.04 20c44cd7596f 2 weeks ago 123MB
ubuntu latest 20c44cd7596f 2 weeks ago 123MB
vskumar@ubuntu:~$
=================>
Let me do some more exercises on housekeeping.
I would like to present some more dependency issues for the above images. You can clearly see the output:
========= Dependencies =======>
vskumar@ubuntu:~$ sudo docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
ubuntu-vmbox latest f6675f4738b7 22 minutes ago 220MB
<none> <none> fc7e4564eb92 7 days ago 169MB
hello-world latest f2a91732366c 12 days ago 1.85kB
ubuntu 16.04 20c44cd7596f 2 weeks ago 123MB
ubuntu latest 20c44cd7596f 2 weeks ago 123MB
vskumar@ubuntu:~$ sudo docker rmi fc7e4564eb92
Deleted: sha256:fc7e4564eb928ccfe068c789f0d650967e8d5dc42d4e8d92409aab6614364075
Deleted: sha256:b16d78406b12e6dbc174f4e71bedb7b9edc0593cad10458ddf042738694c06db
vskumar@ubuntu:~$ sudo docker rmi 20c44cd7596f
Error response from daemon: conflict: unable to delete 20c44cd7596f (cannot be forced) – image has dependent child images
vskumar@ubuntu:~$ sudo docker rmi f6675f4738b7
Error response from daemon: conflict: unable to delete f6675f4738b7 (must be forced) – image is being used by stopped container 1169bb1285cf
vskumar@ubuntu:~$ sudo docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
1169bb1285cf ubuntu-vmbox “/bin/bash” 15 minutes ago Exited (0) 11 minutes ago heuristic_mayer
vskumar@ubuntu:~$
====================>
It means the container “1169bb1285cf ubuntu-vmbox” is the child to image id:f6675f4738b7.
===========>
vskumar@ubuntu:~$ sudo docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
ubuntu-vmbox latest f6675f4738b7 27 minutes ago 220MB
hello-world latest f2a91732366c 12 days ago 1.85kB
ubuntu 16.04 20c44cd7596f 2 weeks ago 123MB
ubuntu latest 20c44cd7596f 2 weeks ago 123MB
vskumar@ubuntu:~$ sudo docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
1169bb1285cf ubuntu-vmbox “/bin/bash” 19 minutes ago Exited (0) 14 minutes ago heuristic_mayer
vskumar@ubuntu:~$
==============>
So if I want to remove Image id: f6675f4738b7, I need to remove the container id:1169bb1285cf , and later I need to remove this image.
$ sudo docker rm container 1169bb1285cf
And later image removal command need to be used as below.
======================>
vskumar@ubuntu:~$ sudo docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
ubuntu-vmbox latest f6675f4738b7 31 minutes ago 220MB
hello-world latest f2a91732366c 12 days ago 1.85kB
ubuntu 16.04 20c44cd7596f 2 weeks ago 123MB
ubuntu latest 20c44cd7596f 2 weeks ago 123MB
vskumar@ubuntu:~$ sudo docker rmi f6675f4738b7
Untagged: ubuntu-vmbox:latest
Deleted: sha256:f6675f4738b721780721f345906a0c78c13a67ee8239a16f071504b217f41658
Deleted: sha256:c07c6f2d2c651dd406977d42d5504c941d7f975a84c8547abaf3869b50942820
Deleted: sha256:4855cfb7ae6f84279bbbfe87e7691377531a541785c613014f64909e6e0f4528
Deleted: sha256:13cd766374bcb31cc0e8cac971e82754bb8e1bc66780abaff264f847e00a94b2
Deleted: sha256:dc6fab8a33a18a8c840e19612253657c4610ab865a26de5a31260f71bcef5f76
vskumar@ubuntu:~$
========================>
So we have the below images only now:
==== Current images ======>
vskumar@ubuntu:~$ sudo docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
hello-world latest f2a91732366c 12 days ago 1.85kB
ubuntu 16.04 20c44cd7596f 2 weeks ago 123MB
ubuntu latest 20c44cd7596f 2 weeks ago 123MB
vskumar@ubuntu:~$
==========================>
We can try to remove the above images:
========= See it is declined due to it is base image ===========>
vskumar@ubuntu:~$ sudo docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
hello-world latest f2a91732366c 12 days ago 1.85kB
ubuntu 16.04 20c44cd7596f 2 weeks ago 123MB
ubuntu latest 20c44cd7596f 2 weeks ago 123MB
vskumar@ubuntu:~$ sudo docker rmi 20c44cd7596f
Error response from daemon: conflict: unable to delete 20c44cd7596f (must be forced) – image is referenced in multiple repositories
vskumar@ubuntu:~$
=========================>
Both ubuntu images are interlinked and they can not be removed as the base docker engine is working on top of their OS.

We will stop this session at this time.

We will continue some more sessions on “dockerfile”.