Nixpert: Docker : Getting Started

Running the first docker container with image : hello-world. This is nothing but just to check your docker setup.

-bash-4.2$ sudo docker run hello-world

Unable to find image 'hello-world:latest' locally

latest: Pulling from library/hello-world

1b930d010525: Pull complete

Digest: sha256:4df8ca8a7e309c256d60d7971ea14c27672fc0d10c5f303856d7bc48f8cc17ff

Status: Downloaded newer image for hello-world:latest

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.

To try something more ambitious, you can run an Ubuntu container with:

$ docker run -it ubuntu bash

Share images, automate workflows, and more with a free Docker ID:

https://hub.docker.com/

For more examples and ideas, visit:

https://docs.docker.com/get-started/

-bash-4.2$ sudo docker images

REPOSITORY TAG IMAGE ID CREATED SIZE

hello-world latest fce289e99eb9 11 months ago 1.84kB

-bash-4.2$ sudo docker ps

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES

Once your setup gets completed, please add the newly created docker user(in this case it is dockmgr) to docker group.

-bash-4.2$ sudo usermod -aG docker dockmgr

-bash-4.2$ id dockmgr

uid=1000(dockmgr) gid=1000(manager) groups=1000(manager),10(wheel),994(docker)

-bash-4.2$

docker run comamnd will check locally for the mentioned image if available it will run a new container upon it, else it will pull the image from docker hub. In this example, We are running a container on ubuntu image and requested docker to provide bash shell.

-bash-4.2$ sudo docker run -it ubuntu /bin/bash

[sudo] password for dockmgr:

Unable to find image 'ubuntu:latest' locally

latest: Pulling from library/ubuntu

7ddbc47eeb70: Pull complete

c1bbdc448b72: Pull complete

8c3b70e39044: Pull complete

45d437916d57: Pull complete

Digest: sha256:6e9f67fa63b0323e9a1e587fd71c561ba48a034504fb804fd26fd8800039835d

Status: Downloaded newer image for ubuntu:latest

root@19f979a29591:/# ls -lrt

total 4

drwxr-xr-x. 8 root root 96 May 23 2017 lib

drwxr-xr-x. 2 root root 6 Apr 24 2018 home

drwxr-xr-x. 2 root root 6 Apr 24 2018 boot

drwxr-xr-x. 1 root root 18 Oct 29 21:25 usr

drwxr-xr-x. 2 root root 6 Oct 29 21:25 srv

drwxr-xr-x. 2 root root 6 Oct 29 21:25 opt

drwxr-xr-x. 2 root root 6 Oct 29 21:25 mnt

drwxr-xr-x. 2 root root 6 Oct 29 21:25 media

drwxr-xr-x. 2 root root 34 Oct 29 21:25 lib64

drwxr-xr-x. 1 root root 17 Oct 29 21:25 var

drwx------. 2 root root 37 Oct 29 21:25 root

drwxr-xr-x. 2 root root 4096 Oct 29 21:25 bin

drwxrwxrwt. 2 root root 6 Oct 29 21:25 tmp

drwxr-xr-x. 1 root root 21 Oct 31 22:20 sbin

drwxr-xr-x. 1 root root 21 Oct 31 22:20 run

dr-xr-xr-x. 13 root root 0 Nov 29 03:30 sys

drwxr-xr-x. 1 root root 66 Nov 29 05:02 etc

dr-xr-xr-x. 122 root root 0 Nov 29 05:02 proc

drwxr-xr-x. 5 root root 360 Nov 29 05:02 dev

To find the docker images available/downloaded locally:

-bash-4.2$ sudo docker images

REPOSITORY TAG IMAGE ID CREATED SIZE

ubuntu latest 775349758637 4 weeks ago 64.2MB

hello-world latest fce289e99eb9 11 months ago 1.84kB

Below command will create a container of ubuntu image as daemon and will print "Hello World" every second.

-bash-4.2$ sudo docker run -d ubuntu /bin/sh -c "while true; do echo Hello World; sleep 1; done"

ad7625e2a5cb886bc40b9e784d0848c2a13c305c27217525405aa6aad06f1959

-bash-4.2$

-bash-4.2$ sudo docker ps

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES

ad7625e2a5cb ubuntu "/bin/sh -c 'while tâ€¦" 9 seconds ago Up 8 seconds objective_diffie

When we create a container a fancy name got allocated to it by docker. Here it is "objective_diffie". If we need to check the logs of the above container running as daemon, we can run:

-bash-4.2$ sudo docker logs objective_diffie

Hello World

To stop a container:

-bash-4.2$ sudo docker stop objective_diffie

objective_diffie

-bash-4.2$ sudo docker ps

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES

-bash-4.2$

Below command is reponsible to download the "training/webapp" image and execute the python code "app.py". As it is a web app, we need to do host-to-container port mapping. So, that we can hit the container port TCP 5000 through host machine web browser at port TCP 80.

-bash-4.2$ sudo docker run -d -p 80:5000 training/webapp python app.py

Unable to find image 'training/webapp:latest' locally

latest: Pulling from training/webapp

Image docker.io/training/webapp:latest uses outdated schema1 manifest format. Please upgrade to a schema2 image for better future compatibility. More information at https://docs.docker.com/registry/spec/deprecated-schema-v1/

e190868d63f8: Pull complete

909cd34c6fd7: Pull complete

0b9bfabab7c1: Pull complete

a3ed95caeb02: Pull complete

10bbbc0fc0ff: Pull complete

fca59b508e9f: Pull complete

e7ae2541b15b: Pull complete

9dd97ef58ce9: Pull complete

a4c1b0cb7af7: Pull complete

Digest: sha256:06e9c1983bd6d5db5fba376ccd63bfa529e8d02f23d5079b8f74a616308fb11d

Status: Downloaded newer image for training/webapp:latest

d78aba119faea05d5feecf2b9a047a36f442c361c832e0311f7770cf7c7bbcf4

-bash-4.2$ sudo docker images

REPOSITORY TAG IMAGE ID CREATED SIZE

ubuntu latest 775349758637 4 weeks ago 64.2MB

hello-world latest fce289e99eb9 11 months ago 1.84kB

training/webapp latest 6fae60ef3446 4 years ago 349MB

-bash-4.2$ sudo docker ps

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES

d78aba119fae training/webapp "python app.py" 27 seconds ago Up 25 seconds 0.0.0.0:80->5000/tcp inspiring_thompson

To view the webpage:

-bash-4.2$ curl http://0.0.0.0:80/

Hello world!-bash-4.2$

From base machine:

http://192.168.29.10:80

To view the container-to-host mapped ports:

-bash-4.2$ sudo docker port d78aba119fae

[sudo] password for dockmgr:

5000/tcp -> 0.0.0.0:80

-bash-4.2$ id

uid=1000(dockmgr) gid=1000(manager) groups=1000(manager),10(wheel) context=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023

-bash-4.2$ sudo docker port d78aba119fae 5000

0.0.0.0:80

-bash-4.2$ sudo docker port inspiring_thompson 5000

0.0.0.0:80

-bash-4.2$

-bash-4.2$ sudo docker stop inspiring_thompson

inspiring_thompson

-bash-4.2$ sudo docker ps

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES

-bash-4.2$

-bash-4.2$ sudo docker run ubuntu /bin/echo "Hello World"

Hello World

-bash-4.2$ sudo docker ps

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES

-bash-4.2$ sudo docker images

REPOSITORY TAG IMAGE ID CREATED SIZE

ubuntu latest 775349758637 4 weeks ago 64.2MB

hello-world latest fce289e99eb9 11 months ago 1.84kB

training/webapp latest 6fae60ef3446 4 years ago 349MB

--name keyword is used to name a container without using the docker defined names:

-bash-4.2$ sudo docker run --name Shantanu ubuntu /bin/echo "Hello World"

Hello World

-bash-4.2$ sudo docker ps

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES

To view the container attributes, docker inspect command has been used. you can get the information about driver, network, etc.

-bash-4.2$ sudo docker inspect Shantanu

[

{

"Id": "3dd11a45ea66efd0e31b7b6495f365b71847262e4b4aea393d8831ff0d88aa91",

"Created": "2019-11-29T05:33:04.274948048Z",

"Path": "/bin/echo",

"Args": [

"Hello World"

"State": {

"Status": "exited",

"Running": false,

"Paused": false,

"Restarting": false,

"OOMKilled": false,

"Dead": false,

"Pid": 0,

"ExitCode": 0,

"Error": "",

"StartedAt": "2019-11-29T05:33:04.903288236Z",

"FinishedAt": "2019-11-29T05:33:04.845752218Z"

"Image": "sha256:775349758637aff77bf85e2ff0597e86e3e859183ef0baba8b3e8fc8d3cba51c",

"ResolvConfPath": "/var/lib/docker/containers/3dd11a45ea66efd0e31b7b6495f365b71847262e4b4aea393d8831ff0d88aa91/resolv.conf",

"HostnamePath": "/var/lib/docker/containers/3dd11a45ea66efd0e31b7b6495f365b71847262e4b4aea393d8831ff0d88aa91/hostname",

"HostsPath": "/var/lib/docker/containers/3dd11a45ea66efd0e31b7b6495f365b71847262e4b4aea393d8831ff0d88aa91/hosts",

"LogPath": "/var/lib/docker/containers/3dd11a45ea66efd0e31b7b6495f365b71847262e4b4aea393d8831ff0d88aa91/3dd11a45ea66efd0e31b7b6495f365b71847262e4b4aea393d8831ff0d88aa91-json.log",

"Name": "/Shantanu",

"RestartCount": 0,

"Driver": "overlay2",

"Platform": "linux",

"MountLabel": "",

"ProcessLabel": "",

"AppArmorProfile": "",

"ExecIDs": null,

"Networks": {

"bridge": {

"IPAMConfig": null,

"Links": null,

"Aliases": null,

"NetworkID": "967757ddd2efc9649725da1708c4c24631d5dc2e9486fcebded5b392d14d3b77",

"EndpointID": "",

"Gateway": "",

"IPAddress": "",

"IPPrefixLen": 0,

"IPv6Gateway": "",

"GlobalIPv6Address": "",

"GlobalIPv6PrefixLen": 0,

"MacAddress": "",

"DriverOpts": null

}

]

docker pull command is used to pull a image from docker hub to your local machine without starting/creating a container:

-bash-4.2$ sudo docker pull centos

Using default tag: latest

latest: Pulling from library/centos

729ec3a6ada3: Pull complete

Digest: sha256:f94c1d992c193b3dc09e297ffd54d8a4f1dc946c37cbeceb26d35ce1647f88d9

Status: Downloaded newer image for centos:latest

docker.io/library/centos:latest

-bash-4.2$ sudo docker ps

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES

-bash-4.2$ sudo docker images

REPOSITORY TAG IMAGE ID CREATED SIZE

ubuntu latest 775349758637 4 weeks ago 64.2MB

centos latest 0f3e07c0138f 8 weeks ago 220MB

hello-world latest fce289e99eb9 11 months ago 1.84kB

training/webapp latest 6fae60ef3446 4 years ago 349MB

-bash-4.2$

The same image can be used to run a container. Here, the centos image which was pulled in the previous step has been used to run a container with /bin/bash shell.

-bash-4.2$ sudo docker run -it centos:latest /bin/bash

[root@2b3c4f44d979 /]# ls -lrt

total 0

drwxr-xr-x. 2 root root 6 May 11 2019 srv

lrwxrwxrwx. 1 root root 8 May 11 2019 sbin -> usr/sbin

drwxr-xr-x. 2 root root 6 May 11 2019 opt

drwxr-xr-x. 2 root root 6 May 11 2019 mnt

drwxr-xr-x. 2 root root 6 May 11 2019 media

lrwxrwxrwx. 1 root root 9 May 11 2019 lib64 -> usr/lib64

lrwxrwxrwx. 1 root root 7 May 11 2019 lib -> usr/lib

drwxr-xr-x. 2 root root 6 May 11 2019 home

lrwxrwxrwx. 1 root root 7 May 11 2019 bin -> usr/bin

drwx------. 2 root root 6 Sep 27 17:13 lost+found

drwxr-xr-x. 12 root root 144 Sep 27 17:13 usr

drwxr-xr-x. 20 root root 262 Sep 27 17:13 var

drwxrwxrwt. 7 root root 145 Sep 27 17:13 tmp

drwxr-xr-x. 11 root root 163 Sep 27 17:13 run

dr-xr-x---. 2 root root 162 Sep 27 17:13 root

dr-xr-xr-x. 13 root root 0 Nov 29 03:30 sys

drwxr-xr-x. 1 root root 66 Nov 29 05:38 etc

dr-xr-xr-x. 122 root root 0 Nov 29 05:38 proc

drwxr-xr-x. 5 root root 360 Nov 29 05:38 dev

[root@2b3c4f44d979 /]# hostname

2b3c4f44d979

[root@2b3c4f44d979 /]# uptime

05:39:02 up 2:08, 0 users, load average: 0.56, 0.22, 0.12

[root@2b3c4f44d979 /]# exit

exit

docker search command is used to search for an image locally & in docker hub.

-bash-4.2$ sudo docker search sinatra

NAME DESCRIPTION STARS OFFICIAL AUTOMATED

training/sinatra 18

tongueroo/sinatra 1

mcansky/sinatra_hello A simple, hello worldly sinatra app in a conâ€¦ 0

gruntwork/sinatra-backend 0

pranay/sinatra FROM ubuntu:14.04 RUN apt-get update && apt-â€¦ 0

marceldegraaf/sinatra Sinatra test app 0

convox/sinatra Convox base image for Sinatra 0 [OK]

franklinyu/sinatra-hello This is a hello-world server built with Sinaâ€¦ 0 [OK]

thoom/sinatra-mock Used to build a Sinatra-backed mock web servâ€¦ 0 [OK]

capttofu/sinatra-with-logstash 0

glazziq/sinatra-ok A simple Sinatra application that will respoâ€¦ 0

gitresolve/sinatra Simple sinatra app for testing 0

arshiagg/sinatra Sinatra web server running a ruby exporter 0

pmblanco/sinatra 0

torico/sinatra-async port 3001. for AWS 0 [OK]

amireh/sinatra Ruby Sinatra with live-reload for developmenâ€¦ 0 [OK]

eventingmonkey/sinatra 0

dancodes/sinatra-heroku-docker An image used to speed up CI builds of Sinatâ€¦ 0 [OK]

esteveavi/sinatra Sinatra example 0

gwjjeff/sinatra 0 [OK]

zoomix/sinatra-galleria 0 [OK]

carlad/sinatra 0

welldoer/sinatra Sinatra webapp 0 [OK]

nilsc/sinatra 0

marceldegraaf/sinatra-with-logstash Sinatra test app with logstash-forwarder to â€¦ 0

-bash-4.2$

To login to your Docker account and to push and pull images from Docker Hub use your Docker ID.

-bash-4.2$ sudo docker login

Login with your Docker ID to push and pull images from Docker Hub. If you don't have a Docker ID, head over to https://hub.docker.com to create one.

Username: shaan2212

Password:

WARNING! Your password will be stored unencrypted in /root/.docker/config.json.

Configure a credential helper to remove this warning. See

https://docs.docker.com/engine/reference/commandline/login/#credentials-store

Your password will be stored unencrypted in /root/.docker/config.json

-bash-4.2$ sudo cat /root/.docker/config.json

{

"auths": {

"https://index.docker.io/v1/": {

"auth": "c2hhYW4yMjEyOlNoYWFuQDIyMTI="

}

"HttpHeaders": {

"User-Agent": "Docker-Client/19.03.5 (linux)"

}

}-bash-4.2$

Pull an image, run a container using it, modify and push it to dockerhub, so that the updated image can be used directly later on. It will save us the overhead to do the repeated things. Here in a centos image we are adding webserver - httpd and binding it as new image while pushing it to dockerhub.

-bash-4.2$ sudo docker run -ti centos /bin/bash

[root@f3bc073ecc85 /]# yum install httpd

Failed to set locale, defaulting to C

CentOS-8 - AppStream 256 kB/s | 6.3 MB 00:25

CentOS-8 - Base 937 kB/s | 7.9 MB 00:08

CentOS-8 - Extras 392 B/s | 2.1 kB 00:05

Dependencies resolved.

==========================================================================================================================

Package Arch Version Repository Size

==========================================================================================================================

Installing:

httpd x86_64 2.4.37-12.module_el8.0.0+185+5908b0db AppStream 1.7 M

Installing dependencies:

apr x86_64 1.6.3-9.el8 AppStream 125 k

apr-util x86_64 1.6.1-6.el8 AppStream 105 k

centos-logos-httpd noarch 80.5-2.el8 AppStream 24 k

httpd-filesystem noarch 2.4.37-12.module_el8.0.0+185+5908b0db AppStream 35 k

httpd-tools x86_64 2.4.37-12.module_el8.0.0+185+5908b0db AppStream 102 k

mod_http2 x86_64 1.11.3-3.module_el8.0.0+185+5908b0db AppStream 158 k

brotli x86_64 1.0.6-1.el8 BaseOS 323 k

mailcap noarch 2.1.48-3.el8 BaseOS 39 k

Installing weak dependencies:

apr-util-bdb x86_64 1.6.1-6.el8 AppStream 25 k

apr-util-openssl x86_64 1.6.1-6.el8 AppStream 27 k

Enabling module streams:

httpd 2.4

Transaction Summary

==========================================================================================================================

Install 11 Packages

Total download size: 2.6 M

Installed size: 7.6 M

Is this ok [y/N]: y

Downloading Packages:

CentOS-8 - AppStream 195% [===========================================================================(1/11): apr-util-bdb-1.6.1-6.el8.x86_64.rpm 66 kB/s | 25 kB 00:00

(2/11): apr-util-1.6.1-6.el8.x86_64.rpm 118 kB/s | 105 kB 00:00

(3/11): apr-1.6.3-9.el8.x86_64.rpm 140 kB/s | 125 kB 00:00

(4/11): apr-util-openssl-1.6.1-6.el8.x86_64.rpm 38 kB/s | 27 kB 00:00

(5/11): centos-logos-httpd-80.5-2.el8.noarch.rpm 87 kB/s | 24 kB 00:00

(6/11): httpd-filesystem-2.4.37-12.module_el8.0.0+185+5908b0db.noarch.rpm 88 kB/s | 35 kB 00:00

(7/11): httpd-tools-2.4.37-12.module_el8.0.0+185+5908b0db.x86_64.rpm 101 kB/s | 102 kB 00:01

(8/11): mod_http2-1.11.3-3.module_el8.0.0+185+5908b0db.x86_64.rpm 121 kB/s | 158 kB 00:01

(9/11): mailcap-2.1.48-3.el8.noarch.rpm 102 kB/s | 39 kB 00:00

(10/11): brotli-1.0.6-1.el8.x86_64.rpm 271 kB/s | 323 kB 00:01

(11/11): httpd-2.4.37-12.module_el8.0.0+185+5908b0db.x86_64.rpm 132 kB/s | 1.7 MB 00:12

--------------------------------------------------------------------------------------------------------------------------

Total 155 kB/s | 2.6 MB 00:17

warning: /var/cache/dnf/AppStream-02e86d1c976ab532/packages/apr-1.6.3-9.el8.x86_64.rpm: Header V3 RSA/SHA256 Signature, key ID 8483c65d: NOKEY

CentOS-8 - AppStream 1.1 MB/s | 1.6 kB 00:00

Importing GPG key 0x8483C65D:

Userid : "CentOS (CentOS Official Signing Key) <security@centos.org>"

Fingerprint: 99DB 70FA E1D7 CE22 7FB6 4882 05B5 55B3 8483 C65D

From : /etc/pki/rpm-gpg/RPM-GPG-KEY-centosofficial

Is this ok [y/N]: y

Key imported successfully

Running transaction check

Transaction check succeeded.

Running transaction test

Transaction test succeeded.

Running transaction

Preparing : 1/1

Installing : apr-1.6.3-9.el8.x86_64 1/11

Running scriptlet: apr-1.6.3-9.el8.x86_64 1/11

Installing : apr-util-bdb-1.6.1-6.el8.x86_64 2/11

Installing : apr-util-openssl-1.6.1-6.el8.x86_64 3/11

Installing : apr-util-1.6.1-6.el8.x86_64 4/11

Running scriptlet: apr-util-1.6.1-6.el8.x86_64 4/11

Installing : httpd-tools-2.4.37-12.module_el8.0.0+185+5908b0db.x86_64 5/11

Installing : mailcap-2.1.48-3.el8.noarch 6/11

Installing : brotli-1.0.6-1.el8.x86_64 7/11

Running scriptlet: httpd-filesystem-2.4.37-12.module_el8.0.0+185+5908b0db.noarch 8/11

Installing : httpd-filesystem-2.4.37-12.module_el8.0.0+185+5908b0db.noarch 8/11

Installing : centos-logos-httpd-80.5-2.el8.noarch 9/11

Installing : mod_http2-1.11.3-3.module_el8.0.0+185+5908b0db.x86_64 10/11

Installing : httpd-2.4.37-12.module_el8.0.0+185+5908b0db.x86_64 11/11

Running scriptlet: httpd-2.4.37-12.module_el8.0.0+185+5908b0db.x86_64 11/11

Verifying : apr-1.6.3-9.el8.x86_64 1/11

Verifying : apr-util-1.6.1-6.el8.x86_64 2/11

Verifying : apr-util-bdb-1.6.1-6.el8.x86_64 3/11

Verifying : apr-util-openssl-1.6.1-6.el8.x86_64 4/11

Verifying : centos-logos-httpd-80.5-2.el8.noarch 5/11

Verifying : httpd-2.4.37-12.module_el8.0.0+185+5908b0db.x86_64 6/11

Verifying : httpd-filesystem-2.4.37-12.module_el8.0.0+185+5908b0db.noarch 7/11

Verifying : httpd-tools-2.4.37-12.module_el8.0.0+185+5908b0db.x86_64 8/11

Verifying : mod_http2-1.11.3-3.module_el8.0.0+185+5908b0db.x86_64 9/11

Verifying : brotli-1.0.6-1.el8.x86_64 10/11

Verifying : mailcap-2.1.48-3.el8.noarch 11/11

Installed:

httpd-2.4.37-12.module_el8.0.0+185+5908b0db.x86_64 apr-util-bdb-1.6.1-6.el8.x86_64

apr-util-openssl-1.6.1-6.el8.x86_64 apr-1.6.3-9.el8.x86_64

apr-util-1.6.1-6.el8.x86_64 centos-logos-httpd-80.5-2.el8.noarch

httpd-filesystem-2.4.37-12.module_el8.0.0+185+5908b0db.noarch httpd-tools-2.4.37-12.module_el8.0.0+185+5908b0db.x86_64

mod_http2-1.11.3-3.module_el8.0.0+185+5908b0db.x86_64 brotli-1.0.6-1.el8.x86_64

mailcap-2.1.48-3.el8.noarch

Complete!

[root@f3bc073ecc85 /]#

Nixpert

Docker : Getting Started

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