What are containers
Isolated environments which helps in running multiple applications in a single machine.
Difference between containers and VMs
VMs have their own OS KERNEL, however, container shares the Host OS Kernel
Different between Docker and Docker Inc?
Docker: Container technology and Container Engine.
Docker Inc: Name of the organisation which open sourced container technology in public domain.
Docker Engine Vs Docker Hub
Docker Engine: Container Engine required to run the containers.
Docker Hub: Image repository for saving Docker images created by the community.
Is it possible to run container engine of Windows on Linux?
No
How to install Docker
- Download Docker installer
- Run Docker installer
- Verify installation by running “docker –version” command
Instructions executed behind the scene, when we run
“docker run debian echo “hello world”?
- It checks for docker image “debian” in local repository.
- If found, it runs the container, if not, download same from Docker Hub and starts running it.
- After starting same, it runs echo command inside the container as the main process.
- Once “Hello world” execution gets completed, it stops the container
When do container stops?
It stops when main process stops.
How to run “interactive” session with container’s bash?
Using “-i” flag:
docker run -i debian /bin/bash
How to attach a “telewriter terminal - tty”, to a container?
Using “-t” flag
docker run -it debian /bin/bash
How to change the hostname of the container?
Using “-h” flag
docker run -it -h debian /bin/bash
Does debian image contains all commands by default?
No, it contains only subset of commands.
It’s default location is /bin
What will happen, if we delete the “/bin” directory?
The container will be useless, as there will be no commands to get execute.
How to list all the containers running in a machine with active state?
docker ps
How to list all the containers running in a machine with active and inactive state?
docker ps -a
How to list all containers with some conditions?
docker ps -f
How to print only IDs of the container during listing?
docker ps -q
What is default name and ID of any container?
Default ID: AlphaNumeric code, which cannot be changed.
Name: Combination of two words separated by underscore.
First word: Adjective
Second word: Name of a famous scientist, Hacker or programmer
How to change the name of the container?
docker run –name
How to get detailed information about a container?
docker inspect
Is it possible to extract required information from “docker inspect output” ?
The output of “docker inspect” command is a JSON.
By using go-lang template, we can extract information from “docker inspect”:
docker inspect –format {{.Network.ip}}
How to get logs from a container?
docker logs
What are different stages of container lifecycle?
running > exited > removed
How to remove a container without volume?
docker rm
