Container Management
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Stopping and Starting Containers
#docker run -it ubuntu /bin/bash
#docker stop <container id>
#docker start <container id>
#docker attach <container id>
Ctlr P Q – To detach from container
#docker ps
#docker ps -a
#docker images
#docker kill <container id>
Note: Docker attach
attaches himself to PID 1, so if shell
is not running we will not get the prompt.
Deleting a Container
Container should be stopped before deleting it.
#docker stop <container id>
#docker rm <container id>
#alias dps=”docker ps”
Low Level Container & Image Info
# docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
testfile latest fa914368ee56 16 hours ago 228 MB
centos latest 98d35105a391 2 weeks ago 192 MB
ubuntu latest 0ef2e08ed3fa 4 weeks ago 130 MB
# docker inspect
fa914368ee56
Above command shows many details like:
ID, Repotags, Created date and time, containerconfig,
various layer info, etc
Getting a Shell in a Container
# docker ps -a
CONTAINER
ID IMAGE COMMAND CREATED STATUS PORTS NAMES
72f512e7e091 ubuntu "/bin/bash" 15 hours ago Exited (0) 15 hours ago dazzling_hypatia
# docker start
72f512e7e091
72f512e7e091
Building from a Docker file
Basics of Dockerfile
- Dockerfile dockerfile DOCKERFILE
- Simple text file
- Contains instructions for how to build image
- Place is important as other files, directories and sub-directories get includes in the container. So, choosing place is very important.
Creating a Dockerfile
It starts from instruction FROM
Every RUN instruction creates a new layer to our image.
Means every Run command launch a new container, run the
command, stop the container and commits the new layer. Next Run command will
use this image and follow the same process as above.
#mkdir /devops
# cat
/devops/Dockerfile
#Ubuntu
- base image
FROM
ubuntu
MAINTAINER
rishibansal02@gmail.com
RUN
apt-get update
CMD
["echo","Hello World"]
Building an Image from the Dockerfile
Go inside the same directory containing Dockerfile.
Here, helloworld, all letters should be in small.
-t = To apply text to the image, not mandatory but
recommended.
#docker build -t
helloworld:1.0 .
Sending build context to Docker
daemon 2.048 kB
Step 1/4
: FROM ubuntu
---> 0ef2e08ed3fa
Step 2/4
: MAINTAINER rishibansal02@gmail.com
---> Running in 410174fdb081
---> 1ec72a6fe42e
Removing
intermediate container 410174fdb081
Step 3/4
: RUN apt-get update
---> Running in 6ee40780f286
……..
……..
Reading
package lists...
---> b2d2ff39eeb7
Removing
intermediate container 6ee40780f286
Step 4/4
: CMD echo Hello World
---> Running in 94078dc48a9d
---> 4f2bd08a0ca9
Removing
intermediate container 94078dc48a9d
Successfully
built 4f2bd08a0ca9
Sending Build context: if there are files and directories in
the same directory it is passwd to docker daemon.
# docker run
helloworld:1.0
Hello World
Running Apache Using Dockerfile
Dockerfile:
FROM centos:7
MAINTAINER Rishi DevOps Batch
LABEL Vendor="CentOS" \
License=GPLv2 \
Version=2.4.6-40
RUN yum -y --setopt=tsflags=nodocs update && \
yum -y
--setopt=tsflags=nodocs install httpd && \
yum clean all
EXPOSE 80
ADD run-httpd.sh /run-httpd.sh
RUN chmod -v +x /run-httpd.sh
CMD ["/run-httpd.sh"]
run-httpd.sh:
#!/bin/bash
# Make sure we're not confused by old, incompletely-shutdown httpd
# context after restarting the container. httpd won't start correctly
# if it thinks it is already running.
rm -rf /run/httpd/* /tmp/httpd*
exec /usr/sbin/apachectl -DFOREGROUND
Build
Command -- (Run at the directory where source files are present)
#docker build -t centos_httpd .
# docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
centos_httpd latest 9a7d6b2e17c3 8 seconds ago 270.7 MB
docker.io/centos latest 36540f359ca3 2 weeks ago 192.5 MB
Run
container:
#docker run -d -p 80:80 centos_httpd
# docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
7b3d1b2b62c5 centos_httpd "/run-httpd.sh" About a minute ago Up About a minute 0.0.0.0:80->80/tcp small_raman
Working with Registries
Creating a Public Repo on Docker Hub
Create a public repo on docker hub.
Only 1 free private repo is allowed.
Create below repo.
rishibansal/helloworld
Pushing image to Docker Hub
# docker images
REPOSITORY TAG
IMAGE ID CREATED SIZE
helloworld 1.0 4f2bd08a0ca9 2 hours ago 170 MB
First we need to tag the image before pushing to
rishibansal/helloworld repo. The first column tells the repo name. So, we need
to tag new image to our new repo.
#docker tag
4f2bd08a0ca9 rishibansal/helloworld
# docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
helloworld 1.0 4f2bd08a0ca9 2 hours ago 170 MB
rishibansal/helloworld 2.0 4f2bd08a0ca9 2 hours ago 170 MB
Before pushing, make sure to login on dokcer hub
# 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: username
Password:
Login
Succeeded
# docker push
rishibansal/helloworld:2.0
The push
refers to a repository [docker.io/rishibansal/helloworld]
23d58913fb58:
Pushed
73e5d2de6e3e:
Pushed
08f405d988e4:
Pushed
511ddc11cf68:
Pushed
a1a54d352248:
Pushed
9d3227c1793b:
Pushed
latest:
digest: sha256:3b7485343c49a41a123415e2ebd6beec2c3bd5f5351076ea85a7ecf52d55a517
size: 1569
# docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
rishibansal/helloworld 2.0 4f2bd08a0ca9 4 hours ago 170 MB
We can see only one layer is pushed. Its because other
layers docker hub took from ubuntu image. So, it’s very intelligent and very
efficient too.
To delete any image, all the containers associated with that
image need to be deleted first.
# docker rm <container id>
#docker rmi <image id>
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