Category Archives: Agile Practices

8. DevOps:How to control and operate docker containers

Docker-logo

In  continuation of my previous blog on “7. DevOps: How to track changes in a container”, in this blog I would like to show some lab practice “How to control and operate docker containers”.

Controlling/operating Docker container:

In this exercise initially, we can see on how to start/stop/restart the containers.

The Docker Engine enables us to start, stop, and restart a container with a set of docker subcommands.

Let me display the docker images:

=======================>

vskumar@ubuntu:~$ sudo service docker status

docker.service – Docker Application Container Engine

Loaded: loaded (/lib/systemd/system/docker.service; enabled; vendor preset: e

Active: active (running) since Sat 2017-11-25 15:09:35 PST; 2min 24s ago

Docs: https://docs.docker.com

Main PID: 1356 (dockerd)

Tasks: 30

Memory: 95.2M

CPU: 3.998s

=========================>

vskumar@ubuntu:~$ sudo docker images

REPOSITORY TAG IMAGE ID CREATED SIZE

hello-world latest f2a91732366c 4 days ago 1.85kB

ubuntu 16.04 20c44cd7596f 8 days ago 123MB

ubuntu latest 20c44cd7596f 8 days ago 123MB

busybox latest 6ad733544a63 3 weeks ago 1.13MB

busybox 1.24 47bcc53f74dc 20 months ago 1.11MB

vskumar@ubuntu:~$

=======================>

Now, I want to launch our container ubuntu 16.04 with start subcommand and experiment with the docker stop subcommand, as given below:

$ sudo docker run -i -t ubuntu:16.04 /bin/bash

======================>
vskumar@ubuntu:~$ 
vskumar@ubuntu:~$ sudo docker run -i -t ubuntu:16.04 /bin/bash
root@d10ad2bd62f7:/# 
======================>
Now, we are with this container in interactive mode.
Let us apply some linux commands as below:
========================>
root@d10ad2bd62f7:/# pwd
/
root@d10ad2bd62f7:/# ls
bin   dev  home  lib64  mnt  proc  run   srv  tmp  var
boot  etc  lib   media  opt  root  sbin  sys  usr
root@d10ad2bd62f7:/# cd home
root@d10ad2bd62f7:/home# ls
root@d10ad2bd62f7:/home# cd ../var
root@d10ad2bd62f7:/var# ls
backups  cache  lib  local  lock  log  mail  opt  run  spool  tmp
root@d10ad2bd62f7:/var# cd tmp
root@d10ad2bd62f7:/var/tmp# pwd
/var/tmp
root@d10ad2bd62f7:/var/tmp# ls
root@d10ad2bd62f7:/var/tmp# cd ../lib
root@d10ad2bd62f7:/var/lib# ls
apt  dpkg  initscripts  insserv  misc  pam  systemd  update-rc.d  urandom
root@d10ad2bd62f7:/var/lib# 
================================>

Now I want to create a file as below in this container:
==================>

root@d10ad2bd62f7:/var/lib# pwd
/var/lib
root@d10ad2bd62f7:/var/lib# cd ../../home
root@d10ad2bd62f7:/home# ls
root@d10ad2bd62f7:/home# touch file1.txt
===================>

Let me add some text into this file as below:
==========>
root@d10ad2bd62f7:/home# echo " Testing containers " > file1.txt
root@d10ad2bd62f7:/home# echo " Applying stop command on containers " > file1.txt
root@d10ad2bd62f7:/home# cat file1.txt
 Applying stop command on containers 
root@d10ad2bd62f7:/home# echo " Testing containers " > file1.txtroot@d10ad2bd62f7:/home# echo " Applying stop command on containers " >> file1.txt
root@d10ad2bd62f7:/home# ls
file1.txt
root@d10ad2bd62f7:/home# ls -l
total 4
-rw-r--r-- 1 root root 59 Nov 25 23:20 file1.txt
root@d10ad2bd62f7:/home# cat file1.txt 
Testing containers 
Applying stop command on containers 
root@d10ad2bd62f7:/home# 
===============>

I have applied some more linux file operations on this container as below:
=================>
root@d10ad2bd62f7:/home#      
root@d10ad2bd62f7:/home# cat file1.txt >> file2.txt
root@d10ad2bd62f7:/home# ls
file1.txt  file2.txt
root@d10ad2bd62f7:/home# ls -l
total 8
-rw-r--r-- 1 root root 59 Nov 25 23:20 file1.txt
-rw-r--r-- 1 root root 59 Nov 25 23:22 file2.txt
root@d10ad2bd62f7:/home# diff file1.txt file2.txt
root@d10ad2bd62f7:/home# echo " Applying restart command also on containers " >> file1.txt
root@d10ad2bd62f7:/home# ls -l
total 8
-rw-r--r-- 1 root root 105 Nov 25 23:23 file1.txt
-rw-r--r-- 1 root root  59 Nov 25 23:22 file2.txt
root@d10ad2bd62f7:/home# diff file1.txt file2.txt3d2
<  Applying restart command also on containers 
root@d10ad2bd62f7:/home# 
====================>
Now, let me apply a stop command on this container and see as 
below by using exit to come out and stop:
=====================>
root@155f4b0764b1:/# 
root@155f4b0764b1:/# exit
exit
vskumar@ubuntu:~$ sudo docker images
REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
hello-world         latest              f2a91732366c        4 days ago          1.85kB
ubuntu              16.04               20c44cd7596f        8 days ago          123MB
ubuntu              latest              20c44cd7596f        8 days ago          123MB
busybox             latest              6ad733544a63        3 weeks ago         1.13MB
busybox             1.24                47bcc53f74dc        20 months ago       1.11MB
vskumar@ubuntu:~$ sudo docker stop  d10ad2bd62f7
d10ad2bd62f7
vskumar@ubuntu:~$ 
=============>
Now, I want to check the containers status using ps -a command as below:
==============>
vskumar@ubuntu:~$ sudo docker ps -a
CONTAINER ID        IMAGE               COMMAND                 CREATED             STATUS                     PORTS               NAMES
155f4b0764b1        ubuntu:16.04        "/bin/bash"             2 minutes ago       Exited (0) 2 minutes ago                       zen_volhard
cb1ff260d48e        ubuntu              "ls /usr/src"           10 hours ago        Exited (0) 10 hours ago                        wonderful_hawking
b20691fd8fb5        ubuntu              "ls /usr"               10 hours ago        Exited (0) 10 hours ago                        friendly_mirzakhani
431ba4c53028        ubuntu              "ls"                    10 hours ago        Exited (0) 10 hours ago                        affectionate_nobel
2c31684bb1f4        ubuntu              "ls -la"                10 hours ago        Exited (0) 10 hours ago                        zealous_meitner
fe2e3b449daf        ubuntu              "ls -la /home/."        10 hours ago        Exited (0) 10 hours ago                        dreamy_shirley
c44bdd05b94d        ubuntu              "ls -la home."          10 hours ago        Exited (2) 10 hours ago                        elastic_pasteur
8b8afa82859a        ubuntu              "ls -la"                10 hours ago        Exited (0) 10 hours ago                        festive_panini
2811eb37af61        ubuntu              "ls -la 604831dbce2a"   10 hours ago        Exited (2) 10 hours ago                        jolly_swartz
604831dbce2a        ubuntu:16.04        "/bin/bash"             10 hours ago        Exited (0) 10 hours ago                        vibrant_ride
718636415a7f        ubuntu:16.04        "/bin/bash"             11 hours ago        Exited (0) 10 hours ago                        reverent_noyce
53a7751d4673        ubuntu:16.04        "/bin/bash"             12 hours ago        Exited (0) 12 hours ago                        musing_chandrasekhar
32bc16b508d4        ubuntu              "bash"                  13 hours ago        Exited (0) 13 hours ago                        eager_goldberg
1dd55efde43f        hello-world         "/hello"                13 hours ago        Exited (0) 13 hours ago                        peaceful_pasteur
a744246ffb8e        hello-world         "/hello"                15 hours ago        Exited (0) 15 hours ago                        naughty_wing
1ba71598b7b8        hello-world         "/hello"                15 hours ago        Exited (0) 15 hours ago                        musing_kare
vskumar@ubuntu:~$ 
===================>
you can see the latest status of our container;
155f4b0764b1        ubuntu:16.04        "/bin/bash"             2 minutes ago       Exited (0) 2 minutes ago                       zen_volhard
It means Docker  maintains in the logs on the usage of containers also.
Now, I want to start the previously stopped container using the docker start subcommand 
by specifying the container ID as an argument, as follows:
$ sudo docker start 155f4b0764b1
===============>
vskumar@ubuntu:~$ sudo docker start 155f4b0764b1
155f4b0764b1
vskumar@ubuntu:~$ 
===============>
Let us check the images status also as below:
==================> Copied the 1st two lines only ----->
vskumar@ubuntu:~$ sudo docker ps -a |more
CONTAINER ID        IMAGE               COMMAND                 CREATED         
    STATUS                      PORTS               NAMES
155f4b0764b1        ubuntu:16.04        "/bin/bash"             10 minutes ago  
    Up About a minute                               zen_volhard
11e293722c64        ubuntu:16.04        "/bin/bash"             12 minutes ago  
    Exited (0) 12 minutes ago  
====================>
It means it shows the current status of the container id:155f4b0764b1 
We need to notice one thing here.

By default, the docker start subcommand will not attach to the container.

We can attach it to the container either using the -a option in the docker start subcommand or by explicitly using the docker attach subcommand.

Now let us try these options.

We will see attach command

$ sudo docker attach 155f4b0764b1
=================>
vskumar@ubuntu:~$ 
vskumar@ubuntu:~$ sudo docker attach 155f4b0764b1
root@155f4b0764b1:/# 
root@155f4b0764b1:/#
=================>
So the attach command brought the container into interactive mode.
Now let me exit it and try the -a option with docker start command:
==================>
root@155f4b0764b1:/home# 
root@155f4b0764b1:/home# exit
exit
===============>
with start -a option:
=============>
vskumar@ubuntu:~$ sudo docker start -a 155f4b0764b1
root@155f4b0764b1:/# 
=================>
After exit, I have tried ps command:
=====================>
vskumar@ubuntu:~$ sudo docker ps
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
155f4b0764b1        ubuntu:16.04        "/bin/bash"         21 minutes ago      Up 3 minutes                            zen_volhard
vskumar@ubuntu:~$ 
======================>
From the above display you can see that its start and current status.
It means the container is active and running.
Now, I want to make another [below] container active.
1dd55efde43f        hello-world         "/hello"                13 hours ago Exited (0) 13 hours ago                        peaceful_pasteur
Let us see the ps command after these 2 containers are in active state.
I want to use the below command:
$ sudo docker start -a 1dd55efde43f
===================>
vskumar@ubuntu:~$ sudo docker start -a 1dd55efde43f

Hello from Docker!
This message shows that your installation appears to be working correctly.

To generate this message, Docker took the following steps:
 1. The Docker client contacted the Docker daemon.
 2. The Docker daemon pulled the "hello-world" image from the Docker Hub.
    (amd64)
 3. The Docker daemon created a new container from that image which runs the
    executable that produces the output you are currently reading.
 4. The Docker daemon streamed that output to the Docker client, which sent it
    to your terminal.

Let us  try something more ambitious, we can run an Ubuntu container with:
 $ docker run -it ubuntu bash

If you want to;
Share images, automate workflows, and more with a free Docker ID:
visit: https://cloud.docker.com/
For more examples and ideas, visit:
https://docs.docker.com/engine/userguide/

vskumar@ubuntu:~$ 
===================>
Please note the above container doesn't have a any os related process to 
keep running continuously. 
Just it displays the message only. Hence 
in the list it will not appear. 
Now, let me list the current processes using docker ps command:
===========>
vskumar@ubuntu:~$ sudo docker ps
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
155f4b0764b1        ubuntu:16.04        "/bin/bash"         32 minutes ago      Up 14 minutes                           zen_volhard
vskumar@ubuntu:~$ 
==============>
So as on now one container is running.

The next set of container controlling subcommands are docker pause and docker unpause.

The docker pause subcommand will freeze the execution of all the processes within the container.

The docker unpause subcommand will unfreeze the execution of all the processes within the container and resume the execution from the point where it was frozen.

Let us try the below command 
$sudo docker pause 155f4b0764b1
========================>
vskumar@ubuntu:~$ 
vskumar@ubuntu:~$ sudo docker pause 155f4b0764b1
155f4b0764b1
vskumar@ubuntu:~$ sudo docker ps
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS                   PORTS               NAMES
155f4b0764b1        ubuntu:16.04        "/bin/bash"         About an hour ago   Up 30 minutes (Paused)                       zen_volhard
vskumar@ubuntu:~$ 
==========================>
You can see the current status as Paused.
Now let me try unpause command also.
$ sudo docker unpause 155f4b0764b1
You can see the total output of this container with pause and unpause statuses:
===================>
vskumar@ubuntu:~$ 
vskumar@ubuntu:~$ sudo docker pause 155f4b0764b1
155f4b0764b1
vskumar@ubuntu:~$ sudo docker ps
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS                   PORTS               NAMES
155f4b0764b1        ubuntu:16.04        "/bin/bash"         About an hour ago   Up 30 minutes (Paused)                       zen_volhard
vskumar@ubuntu:~$ ^C
vskumar@ubuntu:~$ sudo docker unpause 155f4b0764b1
155f4b0764b1
vskumar@ubuntu:~$ sudo docker ps
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
155f4b0764b1        ubuntu:16.04        "/bin/bash"         About an hour ago   Up 32 minutes                           zen_volhard
vskumar@ubuntu:~$ 
======================>
Now, in this lab session finally we will use the stop command:

The container and the script running within it can be stopped using the docker stop subcommand, as shown below:

$ sudo docker stop 155f4b0764b1
=====================> 
vskumar@ubuntu:~$ sudo docker stop 155f4b0764b1
155f4b0764b1
vskumar@ubuntu:~$ sudo docker ps
CONTAINER ID        IMAGE               COMMAND             CREATED STATUS              PORTS               NAMES
=============== It shows there is no active container =============>
Now, let me try with -a and more options.
=========== Partial display is shown here upto the container ===========>
vskumar@ubuntu:~$ sudo docker ps -a |more
CONTAINER ID        IMAGE               COMMAND                 CREATED         
    STATUS                         PORTS               NAMES
f123dbd09116        ubuntu:16.04        "/bin/bash"             6 minutes ago   
    Exited (0) 5 minutes ago                           elastic_nightingale
3cfdea29ce6e        ubuntu              "bash"                  14 minutes ago  
    Exited (0) 14 minutes ago                          gallant_nobel
155f4b0764b1        ubuntu:16.04        "/bin/bash"             About an hour ag
o   Exited (0) 17 seconds ago  
================================>

So far in this lab session, we have seen the differences of different commands to operate and control the containers. I would like to break this session for now. In the next blog we will see on how to manage “Housekeeping containers“.

 Vcard-Shanthi Kumar V

 

DevOps Practices & FAQs -1

Do you think Agile practices are mandatory to implement DevOps Practices ?

Yes, Agile practices bring Continuous delivery [CD] of business requirements through SPRINT. Then these will be converted into different software code and infrastructure. These will be verified and deployed into the production systems.

Fundamental process of SPRINT is; if user gives a requirement to product owner; it will

be decomposed into small chunks of requirements and they will be considered into different SPRINTs [a set of Small technical requirements, where these can be fixed or enhanced in few hours; ex: include or update a formula] and will be presented for verification.

When the DevOps practices are getting implemented; these SPRINTs can be considered to deploy into different technical environments for validating the build and in turn they will be qualified to move into production. This  is an ongoing process by following Continuous Delivery integration [CDI] of Agile. If many developers are there in a Business unit there can be many builds and the users do not need to wait for all of them to complete. The CD can happen. So whichever is completed first it should be delivered. During the CDI the DevOps engineers role is to package the software code and deploy the builds for verification and later on to production. In their activity journey  many tasks can be repeatable. This repeatable activity can be automated with the So called DevOps tools to save manual efforts. This can reduce the deployment cycle time and at the same time total SPRINT delivery time reduction can happen. So the business benefit can be achieved, by pushing the build of specific user requirement faster.

With all the above, without having Agile practices, you can not jump into DevOps practices right away. The people practices on Agile is also very essential.

So if your organization is not having Agile practices in place there is no point of thinking DevOps practices. This can come under old IT tradition.

Look into the below videos on the importance and advantages of DevOps conversion to an IT Company:

 

Below image can denote the transition of IT development cycles till DevOps practice with continuous operation [automated]:

 

DevOps Movement

 

Visit for next series of DevOps FAQs: https://wordpress.com/post/vskumar.blog/1684

Visit for series of Agile interview questions:

https://vskumar.blog/2017/09/04/sdlc-agile-interview-questions-for-freshers-1/

 

Also, Look into some more FAQs:

https://vskumar.blog/2018/12/29/devops-practices-faqs-2-devops-practices-faqs/

https://vskumar.blog/2019/02/01/devops-practices-faqs-3-domain-area/

7. DevOps: How to track changes in a container

Docker-logo

In  continuation of my previous blog on “6. DevOps: How to work with interactive docker containers”, in this blog I would like to show some lab practice “How to track changes in a container”.

Tracking changes inside containers:

Now, let us see the container operations and tracking them.

Let’s launch a container in interactive mode, as we have done in previous session, we can use the below command.

$ sudo docker run -i -t ubuntu:16.04 /bin/bash 
=================>
vskumar@ubuntu:/var/log$ sudo docker run -i -t ubuntu:16.04 /bin/bash  
root@718636415a7f:/# ps
   PID TTY          TIME CMD
     1 pts/0    00:00:00 bash
     9 pts/0    00:00:00 ps
root@718636415a7f:/# ps -ef
UID         PID   PPID  C STIME TTY          TIME CMD
root          1      0  0 12:39 pts/0    00:00:00 /bin/bash
root         10      1  0 12:53 pts/0    00:00:00 ps -ef
root@718636415a7f:/# ls
bin  boot  dev  etc  home  lib  lib64  media  mnt  opt  proc  root  run  sbin  srv  sys  tmp  usr  var
root@718636415a7f:/# 
======================>
Now, let us go to home directory:
========>
root@718636415a7f:/# pwd
/
root@718636415a7f:/# cd home
root@718636415a7f:/home# pwd
/home
root@718636415a7f:/home# ls
root@718636415a7f:/home# 
==============>
Now, as a standalone machine of this docker container, 
I want to create 4 text files using touch command as below:
==============>
root@718636415a7f:/home# ls
root@718636415a7f:/home# ls -l
total 0
root@718636415a7f:/home# touch {vsk1,vsk2,vsk3,vsk4}
root@718636415a7f:/home# ls -l
total 0
-rw-r--r-- 1 root root 0 Nov 25 12:57 vsk1
-rw-r--r-- 1 root root 0 Nov 25 12:57 vsk2
-rw-r--r-- 1 root root 0 Nov 25 12:57 vsk3
-rw-r--r-- 1 root root 0 Nov 25 12:57 vsk4
root@718636415a7f:/home# 
======================>

I am adding some text to each of them as below:

====================>

root@718636415a7f:/home# pwd

/home

root@718636415a7f:/home# echo ‘Testing vsk1’ > vsk1

root@718636415a7f:/home# ls -l

total 4

-rw-r–r– 1 root root 13 Nov 25 13:02 vsk1

-rw-r–r– 1 root root 0 Nov 25 12:57 vsk2

-rw-r–r– 1 root root 0 Nov 25 12:57 vsk3

-rw-r–r– 1 root root 0 Nov 25 12:57 vsk4

root@718636415a7f:/home# echo ‘Testing vsk2’ > vsk2

root@718636415a7f:/home# echo ‘Testing vsk3’ > vsk3

root@718636415a7f:/home# echo ‘NOT Testing vsk4’ > vsk4

root@718636415a7f:/home# ls -l

total 16

-rw-r–r– 1 root root 13 Nov 25 13:02 vsk1

-rw-r–r– 1 root root 13 Nov 25 13:02 vsk2

-rw-r–r– 1 root root 13 Nov 25 13:02 vsk3

-rw-r–r– 1 root root 17 Nov 25 13:02 vsk4

root@718636415a7f:/home#

=====================>

I have created 4 files and added some text into them.

Now, I want to execute a diff command on them:

==========================>

root@718636415a7f:/home# diff vsk1 vsk2

1c1

< Testing vsk1

> Testing vsk2

root@718636415a7f:/home# diff vsk2 vsk3

1c1

< Testing vsk2

> Testing vsk3

root@718636415a7f:/home# echo ‘NOT Testing vsk4’ > vsk1

root@718636415a7f:/home# diff vsk1 vsk4

root@718636415a7f:/home# diff vsk2 vsk4

1c1

< Testing vsk2

> NOT Testing vsk4

root@718636415a7f:/home#

===========================>

Now, I want to exit this container and go back to docker host.

I have detached it using exit.

And back to docker host.

Now, I want to use the diff command as below from host machine to the container:

===========================>

root@718636415a7f:/home# ls -l

total 16

-rw-r–r– 1 root root 17 Nov 25 13:05 vsk1

-rw-r–r– 1 root root 13 Nov 25 13:02 vsk2

-rw-r–r– 1 root root 13 Nov 25 13:02 vsk3

-rw-r–r– 1 root root 17 Nov 25 13:02 vsk4

root@718636415a7f:/home# exit

exit

vskumar@ubuntu:/var/log$ sudo docker diff 718636415a7f

[sudo] password for vskumar:

C /home

A /home/vsk1

A /home/vsk2

A /home/vsk3

A /home/vsk4

C /root

A /root/.bash_history

vskumar@ubuntu:/var/log$

=====================>

The 1st line ‘C /home’ shows; the home directory is modified by showing ‘C’ as changed.

The ‘A’ shows;  before each line denotes the file is added.

If you have a deleted file, it can show as ‘D’ before the file.

Also please let us note here on how docker engine picks up the image with the below priority;

When we work with an image and if we don’t specify that image name, then the latest image (recently generated) will be identified and used by the Docker Engine.

We can check the status of the containers as below using ps -a:

You can see a detailed output from this command from the below display:

==================================>

vskumar@ubuntu:/var/log$ ls

alternatives.log bootstrap.log dmesg fsck kern.log speech-dispatcher unattended-upgrades wtmp

apport.log btmp dpkg.log gpu-manager.log lastlog syslog upstart Xorg.0.log

apt cups faillog hp lightdm syslog.1 vmware Xorg.0.log.old

auth.log dist-upgrade fontconfig.log installer samba syslog.2.gz vmware-vmsvc.log

vskumar@ubuntu:/var/log$ sudo docker ps -a

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES

cb1ff260d48e ubuntu “ls /usr/src” 3 minutes ago Exited (0) 3 minutes ago wonderful_hawking

b20691fd8fb5 ubuntu “ls /usr” 3 minutes ago Exited (0) 3 minutes ago friendly_mirzakhani

431ba4c53028 ubuntu “ls” 3 minutes ago Exited (0) 3 minutes ago affectionate_nobel

2c31684bb1f4 ubuntu “ls -la” 3 minutes ago Exited (0) 3 minutes ago zealous_meitner

fe2e3b449daf ubuntu “ls -la /home/.” 4 minutes ago Exited (0) 4 minutes ago dreamy_shirley

c44bdd05b94d ubuntu “ls -la home.” 4 minutes ago Exited (2) 4 minutes ago elastic_pasteur

8b8afa82859a ubuntu “ls -la” 4 minutes ago Exited (0) 4 minutes ago festive_panini

2811eb37af61 ubuntu “ls -la 604831dbce2a” 4 minutes ago Exited (2) 4 minutes ago jolly_swartz

604831dbce2a ubuntu:16.04 “/bin/bash” 8 minutes ago Exited (0) 6 minutes ago vibrant_ride

718636415a7f ubuntu:16.04 “/bin/bash” 45 minutes ago Exited (0) 18 minutes ago reverent_noyce

53a7751d4673 ubuntu:16.04 “/bin/bash” 2 hours ago Exited (0) 2 hours ago musing_chandrasekhar

32bc16b508d4 ubuntu “bash” 3 hours ago Exited (0) 3 hours ago eager_goldberg

1dd55efde43f hello-world “/hello” 3 hours ago Exited (0) 3 hours ago peaceful_pasteur

a744246ffb8e hello-world “/hello” 5 hours ago Exited (0) 5 hours ago naughty_wing

1ba71598b7b8 hello-world “/hello” 5 hours ago Exited (0) 5 hours ago musing_kare

vskumar@ubuntu:/var/log$

============================>

I would like to terminate the session at this point. In the next blog I would like to present “How to control and operate docker containers”.

Vcard-Shanthi Kumar V-v3

6. DevOps: How to work with interactive Docker containers

Docker-logo

In  continuation of my previous blog on “5. DevOps: How to work with Docker Images”, in this blog I would like to show some lab practice on Interactive Docker containers.

Working with an interactive Docker container:

In the previous lab session, we worked with first Hello World container. And we came to know how the containerization works. Now, we are going to run a container in interactive mode.

What is docker run command ?:

The docker run subcommand takes an image as an input and launches it as a container.

What flags we need to use ?:

We have to pass the -t and -i flags to the docker run subcommand in order to make the container interactive.

The -i flag is the key driver, it makes the container interactive by grabbing the standard input (STDIN) of the container into the terminal.

The -t flag allocates a pseudo-TTY or a pseudo Terminal (Terminal emulator) and then assigns that to the container.

Note: Please note in the earlier session we have executed a container on unbuntu name.

But now, we will explore completely the interactive container operations.

In the below example, we are going to launch an interactive container using the ubuntu:16.04 image and /bin/bash as the command:

$ sudo docker run -i -t ubuntu:16.04 /bin/bash 

=========== Output ============>

vskumar@ubuntu:/var/log$ sudo docker run -i -t ubuntu:16.04 /bin/bash

Unable to find image ‘ubuntu:16.04’ locally

16.04: Pulling from library/ubuntu

Digest: sha256:7c67a2206d3c04703e5c23518707bdd4916c057562dd51c74b99b2ba26af0f79

Status: Downloaded newer image for ubuntu:16.04

root@53a7751d4673:/#

===================>

Why the error messages [Unable to find image] appear ?:

As the ubuntu 16.04 image is not downloaded yet, we get the above message and with the docker run command it will start pulling the ubuntu 16.04 image automatically with following message:

Unable to find image 'ubuntu:16.04' locally
16.04: Pulling from library/ubuntu

When the download is completed, the container will get launched along with the ubuntu:16.04 image.

It will also launch a Bash shell within the container, because we have specified /bin/bash as the command to be executed. This landed us in a Bash prompt, as shown below:

root@53a7751d4673:/#

What is ’53a7751d4673′?:

It is the hostname of the container. In Docker, the hostname is the same as the container ID.

Now, let us run a few commands interactively and confirm what we mentioned about the prompt is correct, as shown below:

To check the hostname below commands need to be executed:

root@53a7751d4673:/# hostname

root@53a7751d4673:/# id

root@53a7751d4673:/# echo $PS1

When we execute them, can see the below output:

==============>

root@53a7751d4673:/#

root@53a7751d4673:/# hostname

53a7751d4673

root@53a7751d4673:/# id

uid=0(root) gid=0(root) groups=0(root)

root@53a7751d4673:/# echo $PS1

\[\e]0;\u@\h: \w\a\]${debian_chroot:+($debian_chroot)}\u@\h:\w\$

root@53a7751d4673:/#

=====================>

So, we have seen the Host name as ’53a7751d4673′.

Id as ‘root ‘

Using ‘PS1’, —>Displays username, hostname and current working directory in the prompt.

PS1 in this example displays the following three information in the prompt:

\[\e]0;\u@\h: \w\a\]${debian_chroot:+($debian_chroot)}\u@\h:\w\$

  • \u – Username
  • \h – Hostname
  • \w – Full path of the current working directory

==============>

root@53a7751d4673:/# pwd

/

root@53a7751d4673:/#

==========>

Note, we are within the ubuntu 16.04 container and it works as Linux machine. So we can try some Linux commands also:

===============>

root@53a7751d4673:/# ps

PID TTY TIME CMD

1 pts/0 00:00:00 bash

26 pts/0 00:00:00 ps

root@53a7751d4673:/# ps -ef

UID PID PPID C STIME TTY TIME CMD

root 1 0 0 11:28 pts/0 00:00:00 /bin/bash

root 27 1 0 11:48 pts/0 00:00:00 ps -ef

root@53a7751d4673:/#

root@53a7751d4673:/# ls

bin boot dev etc home lib lib64 media mnt opt proc root run sbin srv sys tmp usr var

root@53a7751d4673:/# ls -l

total 64

drwxr-xr-x 2 root root 4096 Nov 14 13:49 bin

drwxr-xr-x 2 root root 4096 Apr 12 2016 boot

drwxr-xr-x 5 root root 360 Nov 25 11:28 dev

drwxr-xr-x 45 root root 4096 Nov 25 11:28 etc

drwxr-xr-x 2 root root 4096 Apr 12 2016 home

drwxr-xr-x 8 root root 4096 Sep 13 2015 lib

drwxr-xr-x 2 root root 4096 Nov 14 13:49 lib64

drwxr-xr-x 2 root root 4096 Nov 14 13:48 media

drwxr-xr-x 2 root root 4096 Nov 14 13:48 mnt

drwxr-xr-x 2 root root 4096 Nov 14 13:48 opt

dr-xr-xr-x 250 root root 0 Nov 25 11:28 proc

drwx—— 2 root root 4096 Nov 14 13:49 root

drwxr-xr-x 6 root root 4096 Nov 14 13:49 run

drwxr-xr-x 2 root root 4096 Nov 17 21:59 sbin

drwxr-xr-x 2 root root 4096 Nov 14 13:48 srv

dr-xr-xr-x 13 root root 0 Nov 25 11:28 sys

drwxrwxrwt 2 root root 4096 Nov 14 13:49 tmp

drwxr-xr-x 11 root root 4096 Nov 14 13:48 usr

drwxr-xr-x 13 root root 4096 Nov 14 13:49 var

root@53a7751d4673:/#

================>

So, ubuntu 16.04 container is nothing but a linux machine and we executed the above commands.

Now, I want to change the root permissions as below:

==============>

root@53a7751d4673:/# chmod +777 root

root@53a7751d4673:/# ls -l

total 64

drwxr-xr-x 2 root root 4096 Nov 14 13:49 bin

drwxr-xr-x 2 root root 4096 Apr 12 2016 boot

drwxr-xr-x 5 root root 360 Nov 25 11:28 dev

drwxr-xr-x 45 root root 4096 Nov 25 11:28 etc

drwxr-xr-x 2 root root 4096 Apr 12 2016 home

drwxr-xr-x 8 root root 4096 Sep 13 2015 lib

drwxr-xr-x 2 root root 4096 Nov 14 13:49 lib64

drwxr-xr-x 2 root root 4096 Nov 14 13:48 media

drwxr-xr-x 2 root root 4096 Nov 14 13:48 mnt

drwxr-xr-x 2 root root 4096 Nov 14 13:48 opt

dr-xr-xr-x 255 root root 0 Nov 25 11:28 proc

drwxrwxrwx 2 root root 4096 Nov 14 13:49 root

drwxr-xr-x 6 root root 4096 Nov 14 13:49 run

drwxr-xr-x 2 root root 4096 Nov 17 21:59 sbin

drwxr-xr-x 2 root root 4096 Nov 14 13:48 srv

dr-xr-xr-x 13 root root 0 Nov 25 11:48 sys

drwxrwxrwt 2 root root 4096 Nov 14 13:49 tmp

drwxr-xr-x 11 root root 4096 Nov 14 13:48 usr

drwxr-xr-x 13 root root 4096 Nov 14 13:49 var

root@53a7751d4673:/#

================>

Now, I want to exit from container and come back to host machine.

==================>

root@53a7751d4673:/#

root@53a7751d4673:/# exit

exit

vskumar@ubuntu:/var/log$

===============>

Whenever the Bash exit command is used in the interactive container, it will terminate the Bash shell process.

In turn it will stop the container and returns to the docker host machine.

As a result, we can see the Docker host’s prompt $


You can see the status of docker images as below when I used ‘sudo docker images’ :

==================>

vskumar@ubuntu:/var/log$

vskumar@ubuntu:/var/log$ sudo docker images

REPOSITORY TAG IMAGE ID CREATED SIZE

hello-world latest f2a91732366c 4 days ago 1.85kB

ubuntu 16.04 20c44cd7596f 7 days ago 123MB

ubuntu latest 20c44cd7596f 7 days ago 123MB

busybox latest 6ad733544a63 3 weeks ago 1.13MB

busybox 1.24 47bcc53f74dc 20 months ago 1.11MB

vskumar@ubuntu:/var/log$

=====================>

You can see whatever containers; we have have used in the past exercises.

At this point, I would like to stop this lab session. And in the next blog we can see on “How to track changes in a container?”.

 

Vcard-Shanthi Kumar V

 

 

4. DevOps: How to create and work with Docker Containers

Docker-logo

In continuation of my previous blog on 2. DevOps: How to install Docker 17.03.0 community edition and start working with it on Ubuntu 16.x VM [https://vskumar.blog/2017/11/25/2-devops-how-to-install-docker-17-03-0-community-edition-and-start-working-with-it-on-ubuntu-16-x-vm/], in this blog I would like to cover the lab practice on Docker containers.

Assuming you have the same setup as we did in the previous lab session,

using the below subcommand, you can view the current image hello-world

Use the below command:

sudo docker run -it hello-world

$docker history hello-world

You can run this image and see:

======================>

vskumar@ubuntu:~$ sudo docker history hello-world

[sudo]

password for vskumar:
IMAGE CREATED CREATED BY SIZE COMMENT
f2a91732366c 5 days ago /bin/sh -c #(nop) CMD [“/hello”] 0B
<missing> 5 days ago /bin/sh -c #(nop) COPY file:f3dac9d5b1b0307f… 1.85kB
vskumar@ubuntu:~$

======================>

Check the current docker information:

sudo docker info |more

======================================>

vskumar@ubuntu:~$ sudo docker info |more
Containers: 2
Running: 1
Paused: 0
Stopped: 1
Images: 6
Server Version: 17.11.0-ce
Storage Driver: aufs
Root Dir: /var/lib/docker/aufs
Backing Filesystem: extfs
Dirs: 14
Dirperm1 Supported: true
Logging Driver: json-file
Cgroup Driver: cgroupfs
Plugins:
Volume: local
Network: bridge host macvlan null overlay
Log: awslogs fluentd gcplogs gelf journald json-file logentries splunk syslog
Swarm: inactive
Runtimes: runc
Default Runtime: runc
Init Binary: docker-init
containerd version: 992280e8e265f491f7a624ab82f3e238be086e49
runc version: 0351df1c5a66838d0c392b4ac4cf9450de844e2d
–More–WARNING: No swap limit support
init version: 949e6fa
Security Options:
apparmor
seccomp
Profile: default
Kernel Version: 4.10.0-40-generic
Operating System: Ubuntu 16.04.3 LTS
OSType: linux
Architecture: x86_64
CPUs: 1
Total Memory: 1.933GiB
Name: ubuntu
ID: KH7E:PWA2:EJGE:MZCA:3RVJ:LU2W:BA7S:DTIQ:32HP:XXO7:RXBR:4XQI
Docker Root Dir: /var/lib/docker
Debug Mode (client): false
Debug Mode (server): false
Registry: https://index.docker.io/v1/
Experimental: false
Insecure Registries:
127.0.0.0/8
Live Restore Enabled: false

vskumar@ubuntu:~$

=============================>

Now, let us work on the Docker images operations:

In the previous session, we demonstrated the typical Hello World example using the
hello-world image.

you can run an Ubuntu container with:

$ sudo docker run -it ubuntu bash

you can run an Ubuntu container with:

======= We are in Docker container =====>

vskumar@ubuntu:~$ sudo docker run -it ubuntu bash
root@10ffea6140f9:/#

============>

Now, let us apply some Linux commands as below:

==================>

root@10ffea6140f9:/# ls
bin dev home lib64 mnt proc run srv tmp var
boot etc lib media opt root sbin sys usr
root@10ffea6140f9:/# ps -a
PID TTY TIME CMD
11 pts/0 00:00:00 ps
root@10ffea6140f9:/# ps -ef
UID PID PPID C STIME TTY TIME CMD
root 1 0 0 05:36 pts/0 00:00:00 bash
root 12 1 0 05:38 pts/0 00:00:00 ps -ef
root@10ffea6140f9:/# cd lib
root@10ffea6140f9:/lib# ls
init lsb systemd terminfo udev x86_64-linux-gnu
root@10ffea6140f9:/lib# cd ..
root@10ffea6140f9:/# cd var
root@10ffea6140f9:/var# pwd
/var
root@10ffea6140f9:/var# ls
backups cache lib local lock log mail opt run spool tmp
root@10ffea6140f9:/var# cd log
root@10ffea6140f9:/var/log# ls
alternatives.log bootstrap.log dmesg faillog lastlog
apt btmp dpkg.log fsck wtmp

root@10ffea6140f9:/var/log# cat dpkg.log |more
2017-11-14 13:48:30 startup archives install
2017-11-14 13:48:30 install base-passwd:amd64 <none> 3.5.39
2017-11-14 13:48:30 status half-installed base-passwd:amd64 3.5.39
2017-11-14 13:48:30 status unpacked base-passwd:amd64 3.5.39
2017-11-14 13:48:30 status unpacked base-passwd:amd64 3.5.39
2017-11-14 13:48:30 configure base-passwd:amd64 3.5.39 3.5.39
2017-11-14 13:48:30 status unpacked base-passwd:amd64 3.5.39
2017-11-14 13:48:30 status half-configured base-passwd:amd64 3.5.39
2017-11-14 13:48:30 status installed base-passwd:amd64 3.5.39
2017-11-14 13:48:30 startup archives install
2017-11-14 13:48:30 install base-files:amd64 <none> 9.4ubuntu4
2017-11-14 13:48:30 status half-installed base-files:amd64 9.4ubuntu4
2017-11-14 13:48:30 status unpacked base-files:amd64 9.4ubuntu4
2017-11-14 13:48:30 status unpacked base-files:amd64 9.4ubuntu4
2017-11-14 13:48:30 configure base-files:amd64 9.4ubuntu4 9.4ubuntu4
2017-11-14 13:48:30 status unpacked base-files:amd64 9.4ubuntu4
2017-11-14 13:48:30 status unpacked base-files:amd64 9.4ubuntu4
2017-11-14 13:48:30 status unpacked base-files:amd64 9.4ubuntu4
2017-11-14 13:48:30 status unpacked base-files:amd64 9.4ubuntu4
2017-11-14 13:48:30 status unpacked base-files:amd64 9.4ubuntu4
2017-11-14 13:48:30 status unpacked base-files:amd64 9.4ubuntu4
2017-11-14 13:48:30 status unpacked base-files:amd64 9.4ubuntu4
2017-11-14 13:48:30 status unpacked base-files:amd64 9.4ubuntu4

root@10ffea6140f9:/var/log#

==================================>

WE have seen this container like a Linux machine only.

Now, to come out into Docker use ‘exit’ command.

====================>

root@10ffea6140f9:/var/log#
root@10ffea6140f9:/var/log# exit
exit
vskumar@ubuntu:~$

vskumar@ubuntu:~$ sudo docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
docker-exercise/ubuntu-wgetinstall latest e34304119838 4 hours ago 169MB
<none> <none> fc7e4564eb92 4 hours ago 169MB
hello-world latest f2a91732366c 5 days ago 1.85kB
ubuntu 16.04 20c44cd7596f 8 days ago 123MB
ubuntu latest 20c44cd7596f 8 days ago 123MB
busybox latest 6ad733544a63 3 weeks ago 1.13MB
busybox 1.24 47bcc53f74dc 20 months ago 1.11MB
vskumar@ubuntu:~$

======================>

It means earlier when we run the command ‘$ sudo docker run -it ubuntu bash’ it went into terminal interactive mode of unbuntu container. When we applied ‘exit’ it came out from that container to ‘docker’ . Now through docker we have seen the list of docker images.

So, we have seen from the above session the container usage and the docker images.

Now, let us check the docker services status as below:

$sudo service docker status

vskumar@ubuntu:/var/tmp$ sudo service docker status

================================>

docker.service – Docker Application Container Engine

Loaded: loaded (/lib/systemd/system/docker.service; enabled; vendor preset: e

Active: active (running) since Sat 2017-11-25 02:07:54 PST; 25min ago

Docs: https://docs.docker.com

Main PID: 1224 (dockerd)

Tasks: 18

Memory: 255.2M

CPU: 35.334s

CGroup: /system.slice/docker.service

├─1224 /usr/bin/dockerd -H fd://

└─1415 docker-containerd –config /var/run/docker/containerd/containe

================================>

Now, we will stop this session at this point in the next block we will learn how to download public docker image and work with images and containers.

Vcard-Shanthi Kumar V-v3

2. DevOps: How to install Docker 17.03.0 community edition and start working with it on Ubuntu 16.x VM

Docker-logo.png

In this blog, I would like to demonstrate the Docker 17.03.0  CE edition installation on Ubuntu 16.0.4 VM machine. And later on little practice can be shown  using containers in a series of blogs. Please keep visiting for weekly new blogs or subscribe it. If you are interested to follow this site blogs, please send e-mail [with your linkedin message ] to approve with authentication.

Assume you have an unbuntu machine or a Virtual machine [VM] configured. And in this blog you can see on how to install the Docker 17.03.0  CE [as on this blog’s date] with screen display outputs:

$ sudo service docker restart

However, if the Active column shows inactive or maintenance as the status, your Docker service is not running. In such cases, restart the Docker service, as shown here:

$ sudo service docker restart 
 
Install Docker on Unbuntu:

1.Add the Docker package repository path for Ubuntu 16.04 to your APT sources, as shown below:
 $ sudo sh -c "echo deb https://apt.dockerproject.org/repo \
 ubuntu-xenial main > /etc/apt/sources.list.d/docker.list"

2.Add the GNU Privacy Guard (GPG) key by  running the following command:
 $ sudo apt-key adv --keyserver \
 hkp://p80.pool.sks-keyservers.net:80 --recv-keys \ 
 
If the above format is expired; you can try as below:
==== Alternate method with screen output ====>
$sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 58118E89F3A912897C070ADBF76221572C52609D

Executing: /tmp/apt-key-gpghome.YU0Rk7y5kX/gpg.1.sh --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 58118E89F3A912897C070ADBF76221572C52609D
gpg: key F76221572C52609D: 7 signatures not checked due to missing keys
gpg: key F76221572C52609D: public key "Docker Release Tool (releasedocker) <docker@docker.com>" imported
gpg: Total number processed: 1
gpg:               imported: 1
=========================================>
The above format should work. Even if that is not working, please google the same keys for the latest validated keys.

3.Resynchronize with the package repository using the below command:
 $ sudo apt-get update
Now docker software is in your unbuntu machine.

4. Now, you can Install Docker and start  Docker service:
 $ sudo apt-get install -y docker-engine

5.Now you have  installed the Docker Engine, we need to  verify our installation by running docker --version as shown below:
 $ docker --version

We have successfully installed Docker version 17.03.0 community edition.
Other options is; in a single script by avoiding the above steps you can install it:

If you are working on Ubuntu, follow the below command:

==================== Screen output ==========>
vskumar@ubuntu:/var/log$ sudo wget -qO- https://get.docker.io/ | sh |more
[sudo] password for vskumar: 
# Executing docker install script, commit: 11aa13e
Warning: the "docker" command appears to already exist on this system.
If you already have  installed Docker, this script can cause trouble, which is
why we're displaying this warning and provide the opportunity to cancel the
installation.
If you installed the current Docker package using this script and are using it
again to update Docker, you can safely ignore this message.
You may press Ctrl+C now to abort this script.
+ sleep 20
+ sudo -E sh -c apt-get update -qq >/dev/null
============== Since I have already installed, I have breaked this process ====>
But, if you try this script; it takes some time to download and install docker for the whole process. 
Be patient to see the final result.  Later check the docker version to reconfirm. Using the below command.
$docker --version

It is very easy to install docker with the above step(s) in your Ubuntu machine.

Assuming you have studied the theory part of docker usage I am moving forward to lab practice.

Now, let us do some practice with docker images/containers.

We will do the below steps:

1. Downloading the first Docker image:
we will download a sample hello-world docker image using the following command:
$ sudo docker pull hello-world

2. Once the image is downloaded, 
they can be verified using the docker images subcommand, as given below:
To check the image run the below command:
$sudo docker run hello-world
It displays the message “Hello from Docker!”
You have set up your first Docker container and it is running now.

3. How to Troubleshoot with Docker containers?:
If you want to troubleshoot with container, the first step is  to check the Docker's running status by using the below command:
$ sudo service docker status 
It displays the status and shows as Docker 'Active running' message on the screen along with other messages.
Press ctrl+C to come out from the display.

=========== Partial content from the above command =====>
vskumar@ubuntu:/var/log$ sudo service docker status 
● docker.service - Docker Application Container Engine
Loaded: loaded (/lib/systemd/system/docker.service; enabled; vendor preset: enabled)
Active: active (running) since Sat 2017-11-25 02:54:42 PST; 3h 56min ago
Docs: https://docs.docker.com
Main PID: 3769 (dockerd)
Tasks: 19
Memory: 43.6M
CPU: 1min 21.184s
CGroup: /system.slice/docker.service
├─3769 /usr/bin/dockerd -H fd://
└─3778 docker-containerd --config /var/run/docker/containerd/containerd.toml
===============================>
For some reasons, if the Active column shows inactive or maintenance as the status, it means your Docker service is not running. 
In that case to restart the Docker service, use the below command:

$ sudo service docker restart

We will see in the next blog, some more exercises on Docker containers and images.

Vcard-Shanthi Kumar V-v3

 

 

 

 

 

 

 

 

 

 

Did you check the Agile entry criteria before your initiation ?

Agile Entry Critera - Check-Page1 Agile Entry Critera-Code refactor-simulation-chart-Page2Agile Entry Critera - Check-Page3 I have made videos on this blog and  posted in the below youtube  channel URL with further elaboration: http://www.youtube.com/channel/UCR1qBu2xUiypGDa2UaNQr8A/videos

If you are keen in getting my support on these practices implementation for your Agile programmes/projects/teams, please contact me.

I support the organizations globally.

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