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131 lines
4.8 KiB
Markdown
131 lines
4.8 KiB
Markdown
---
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title: Useful commands for Docker
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---
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# Useful commands for Docker
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- Docker is mainly used for run programs on server side.
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- Companies customize their OS before use. They don't require many things like GUI.
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- Less program means less RAM used and more security.
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- More features means more chances to hack, more vulnerabilities.
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- We use OS to run program. Docker gives us an environment to run our program.
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## Installing docker-engine
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### For Redhat OS
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- First, setup yum repo
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```
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[docker]
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baseurl = https://yum.dockerproject.org/repo/main/centos/7
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gpgcheck=0
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```
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- Then, install **docker-engine**
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`$ yum install docker-engine`
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### Start the services of docker
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`$ systemctl restart docker`
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It starts the docker server.
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### See all the images available in docker
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`$ docker images`
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The default _docker images_ will show all top level images, their repository and tags, and their size.
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### Load an image in docker
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`$ docker load -i ubuntu-14.04.tar`
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- **i** - Read from tar archive file, instead of STDIN
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It loads an image or repository from a tar archive (even if compressed with gzip, bzip2, or xz) from a file or STDIN. It restores both images and tags.
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### Docker run reference
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- Docker runs processes in isolated containers.
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- A container is a process which runs on a host. The host may be local or remote.
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- When an operator executes `docker run`, the container process that runs is isolated in that it has its own file system, its own networking, and its own isolated process tree separate from the host.
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### Run or start a new OS
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`$ docker run -it ubuntu:14.04`
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- The `docker run` command first `creates` a writeable container layer over the specified image, and then `starts` it using the specified command.
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- The above example runs a container using the `ubuntu:14.04` image. The `-it` instructs Docker to allocate a pseudo-TTY connected to the container’s stdin; creating an interactive `bash` shell in the container.
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### See all the running OSs
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`$ docker ps`
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- The `docker ps` command only shows running containers by default.
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- To see all containers, use the `-a` (or `--all`) flag:
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`$ docker ps -a`
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### Come out from docker OS console
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`exit`
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### From shell of docker OS, for coming out without exiting container
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press _ctrl + p + q_
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### From terminal of base system, to run a command in docker OS
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`$ docker exec mycontainer ifconfig`
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- **mycontainer** is the name of container.
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- The `docker exec` command runs a new command in a running container.
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### Usually run docker using this command
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`$ docker run –dit ubuntu:14.04`
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- **i** - interactive
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- **t** - terminal
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- **d** - detach
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### Stop all running OSs
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```
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$ docker ps -q //shows id of every running OS
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$ docker stop $(docker ps -q)
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```
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### Permanently remove a container
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`$ docker rm id`
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### Permanently Remove all the stopped containers
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`$ docker rm $(docker ps -a -q)`
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- This command will delete all stopped containers.
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- The command `docker ps -a -q` will return all existing container IDs and pass them to the `rm` command which will delete them.
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- Any running containers will not be deleted.
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### Remove containers while running (forcefully)
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`$ docker rm -f $(docker ps -a -q)`
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### Giving docker OS a name when starting
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- By default, docker gives unique name to every container with a unique id.
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- We can also give a name to container using following command -
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`$ docker run -it --name adarsh centos:latest`
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### Copy a file in container
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`$ docker cp /root/form.txt myconatiner:/`
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This command will copy a file form.txt from the base system to the specified container.
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### Download docker images
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[docker hub](http://hub.docker.com) - All the available docker images can be downloaded from this URL.
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### Check different versions of OS that are available
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```
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$ docker search ubuntu //search
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$ docker pull ubuntu:17.10 //downlaod required version
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```
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## Docker Storage
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### Basic Storage types
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1. **Empheral disk (temporary)** – OS removal will remove data (like windows C drive)
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2. **Persistent disk (permanent)** - OS removal will not erase data (like windows D drive)
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- **-v** gives persistent storage. OS removal will not remove data.
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### Docker volume manager
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Docker by default takes space from **/** drive of host system to store data. Overall **/** drive amount of storage docker can use.
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### Give separate space to a docker container
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- Make a partition, format it and mount in base system.
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Let the partition created is **mypart**
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- Then, run following command
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`$ docker run –it -v /mypart:/data centos`
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- **mypart** is a partition in base system and **data** is the folder where docker will store its data.
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- **v** - volume
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### Attaching dvd to a container
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`$ docker run –it –v /run/media/root/RHEL-7.3\ Server.. centos`
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This command will attach a RHEL to the container.
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### Copy content from a folder of base system to _/data_ in docker centos
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`$ docker run –it -v /folder_name:/data centos` |