Docker Tutorial

Install docker on Ubuntu

Installation guild is in:

https://docs.docker.com/engine/installation/linux/ubuntu/#install-from-a-package

1.       

To install Docker CE, you need the 64-bit version of one of these Ubuntu versions:

• Zesty 17.04
•  Xenial 16.04 (LTS)
•  Trusty 14.04 (LTS)

check OS version:

vagrant@exp:/devops/PPM/942$ cat /etc/*-release

 2.       

wget https://download.docker.com/linux/ubuntu/dists/xenial/pool/stable/amd64/docker-ce_17.06.0~ce-0~ubuntu_amd64.deb  --verbose -P /tmp

 3.   

sudo dpkg -i /tmp/docker-ce_17.06.0~ce-0~ubuntu_amd64.deb

If run into this issue:

dpkg: dependency problems prevent configuration of docker-ce:

 docker-ce depends on libltdl7 (>= 2.4.6); however:

  Package libltdl7 is not installed.

Solution:

sudo apt-get update

sudo apt-get install libltdl7

Setup proxy

When you download a docker image, and run into issue docker:

Error response from daemon: Get https://registry-1.docker.io/v2/: net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers).

This is because you are running docker behind a proxy, and need to setup proxy for docker

Solution:

https://docs.docker.com/engine/admin/systemd/#httphttps-proxy

sudo mkdir -p /etc/systemd/system/docker.service.d

      sudo vim /etc/systemd/system/docker.service.d/http-proxy.conf

[Service]

Environment="HTTP_PROXY=YOUR_PROXY" "HTTPS_PROXY=YOUR_PROXY" "http_proxy=YOUR_PORXY" "https_proxy=YOUR_PROXY" "no_proxy=localhost,192.168.33.11,127.0.0.1" "NO_PROXY=localhost,192.168.33.11,127.0.0.1"

Flush changes

sudo systemctl daemon-reload

Check changes are effective

systemctl show --property=Environment docker

Restart docker service

sudo systemctl restart docker

Run Tomcat

Choose an image:

https://hub.docker.com/_/tomcat/

docker run command:

https://docs.docker.com/engine/reference/run/

Run tomcat:

sudo docker run -it --name mytomcat1 -p 8080:8080 tomcat:8.0

This may take a long time to download the image.

Check container status:

sudo docker ps -a

(-a check all containers, without it, will only check running containers)

Check image:

sudo docker image ls

Start/stop container:

sudo docker start mytomcat1

sudo docker stop mytomcat1

sudo docker restart mytomcat1

Check container logs:

sudo docker logs -f mytomcat1

Find out the process running inside docker:

ubuntu@exp1:~$ sudo docker top mytomcat1

UID                 PID                 PPID                C                   STIME               TTY                 TIME                CMD

root                5566                5549                0                   07:34               ?                   00:00:04            /docker-java-home/jre/bin/java -Djava.util.logging.config.file=/usr/local/tomcat/conf/logging.properties -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager -Djdk.tls.ephemeralDHKeySize=2048 -Djava.protocol.handler.pkgs=org.apache.catalina.webresources -Djava.endorsed.dirs=/usr/local/tomcat/endorsed -classpath /usr/local/tomcat/bin/bootstrap.jar:/usr/local/tomcat/bin/tomcat-juli.jar -Dcatalina.base=/usr/local/tomcat -Dcatalina.home=/usr/local/tomcat -Djava.io.tmpdir=/usr/local/tomcat/temp org.apache.catalina.startup.Bootstrap start

Go inside the container:  

sudo docker exec -it mytomcat1 /bin/sh

#pwd

(working directory from Dockerfile)

Find out the processing running inside docker:

# ps -fwww 1

UID        PID  PPID  C STIME TTY      STAT   TIME CMD

root         1     0  1 07:40 ?        Ssl    0:03 /docker-java-home/jre/bin/java -Djava.util.logging.config.file=/usr/local/tomcat/conf/logging.properties -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager -Djdk.tls.ephemeralDHKeySize=2048 -Djava.protocol.handler.pkgs=org.apache.catalina.webresources -Djava.endorsed.dirs=/usr/local/tomcat/endorsed -classpath /usr/local/tomcat/bin/bootstrap.jar:/usr/local/tomcat/bin/tomcat-juli.jar -Dcatalina.base=/usr/local/tomcat -Dcatalina.home=/usr/local/tomcat -Djava.io.tmpdir=/usr/local/tomcat/temp org.apache.catalina.startup.Bootstrap start

#cd logs

#touch abc.abc

#exit

Restart and go inside mytomcat1, logs/abc.abc is still there

Remove container:

sudo docker rm mytomcat1

Recreate container:

sudo docker run -it --name mytomcat1 -p 8080:8080 tomcat:8.0

Access tomcat

http://192.168.33.10:8080/

Run another tomcat container with volume:

sudo docker run -d --name mytomcat2 -p 8081:8080 -v /devops/mytomcat/logs:/usr/local/tomcat/logs tomcat:8.0

Check host folder /devops/mytomcat/logs, see it has tomcat logs

Share volumes among dockers:

sudo docker run -d --name mytomcat2 -p 8081:8080 -v /devops/mytomcat/logs:/usr/local/tomcat/logs tomcat:8.0

sudo docker run -d --name mytomcat3 -p 8082:8080 --volumes-from mytomcat2 tomcat:8.0

Debug Docker Daemon

Change debug to true:

sudo vim /etc/docker/daemon.json

{

  "debug": true,

}

Restart docker:

sudo systemctl restart docker

check docker log:

sudo journalctl -fu docker.service