# Managing Docker Containers

## 1\. Container Commands

### 1\. Create a new container using the below command

```plaintext
sudo docker run -it ubuntu /bin/bash
```

* The "docker run" command provides all launching capabilities for docker to create a container. We use docker run to create new containers.
    
* \-i: open STDIN from the container
    
* \-t: tells docker to assign a pseudo-tty to the container
    
* \-it : provides an interactive shell
    
* ubuntu: ubuntu is an image and also called as "stock image" or "base image". This image will be downloaded from Docker hub when we run 'docker run' command first time
    
* /bin/bash: 'shell program' that will be installed in the terminal
    

### 2\. Inspect the new container

Let's believe that it's a separate machine by using the below commands

1. hostname
    
2. cat /etc/hosts
    
3. hostname -i
    
4. ps -ef
    

### 3\. SSH setup for containers

Setup SSH in the containers so that they can communicate with each other

1. Create two containers having IP addresses - 172.17.0.2, 172.17.0.3
    
2. Try to connect to 172.17.0.3 from 172.17.0.2 using the below command. You will get an error.
    
    `$ ssh demo@172.17.0.3` (you won't be able to connect by default)
    
3. Install ssh server
    
    `$ apt-get update`
    
    `$ apt-get install openssh-server`
    
4. Start the server
    
    `$ service ssh start` (status/stop/restart)
    
5. Create a user and set up a password
    
    `$ useradd -m -d /home/demo -s /bin/bash demo`
    
    `$ passwd demo`
    
6. Connect to the container using ssh from 172.17.0.2 or any other machine.
    
    `$ ssh demo@172.17.0.3`
    
7. Enable root user over ssh
    
    Add the below line under "# Authentication:" in "/etc/ssh/sshd\_config" `PermitRootLogin yes`
    

### 4\. Shutdown a container

"exit" to stop the container

### 5\. Log in to a stopped container

`$docker start`

`$docker attach`

### 6\. List all containers(stopped and running)

`$ docker container ls -a`

`$ docker ps -a`

### 7\. List given no. of containers

`$ docker ps -a -n1`

### 8\. List running containers only

`$ docker container ls`

`$ docker ps`

### 9\. List Stopped containers only

`$ docker container ls -f status=exited` (Where Status can be exited/running)

The "docker container ls" command output shows:

\- Image name from which container is created

\- ID - the container can be identified using short UUID, longer UUID Or name.

\- Status of the container (Up / Exited)

\- Name of the container

### 10\. Show the last container which you have created (stopped/running)

`$ docker container ls -l`

### 11\. Naming the container

`$ docker run --name demo -it ubuntu /bin/bash`

Note: Two containers can't have the same name.

### 12\. Rename a container

`$ docker rename container_name_1 container_name_2`

### 13\. Deleting a container by giving its name or ID

`$ docker rm ID/name`

### 14\. Delete all (running/stopped) containers at once

`$ docker rm -f $(docker container ls -a -q)`

`$ docker rm -f $(docker ps -a -q)`

### 15\. Delete running containers only

`$ docker rm -f $(docker container ls -q)`

`$ docker rm -f $(docker ps -q)`

### 16\. List stopped containers only

`$ docker container ls -a -f status=exited`

### 17\. Starting a stopped container

`$ docker start container_name`

### 18\. Attaching to a running container

`$ docker attach container_name (OR)`

`$ docker attach b1b1c8dc1939`

### 19\. Run a Linux command remotely in a container Or Get an independent terminal from a container remotely (from the Host)

`$ docker exec -it tomcat-server ps -ef`

### 20\. Stopping a container from the 'host machine'

`$ docker stop container_name`(Gracefully stop the container)

`$ docker kill container_name`(Forcibly stop the container)

### 21\. Inspecting the container's processes from the host machine

`$ docker top container_name`

### 22\. Show the last 4 containers (stopped/running)

`$ docker ps -n4`

### 23\. Create a container in a background mode ( without terminal access )

`$ docker run -it -d ubuntu /bin/bash`

### 24\. Find More About The Container

The 'docker inspect' command interrogates the container and returns complete information about it.

Ex: image name, IP, Memory details, hostname ..etc

Examples:

`$ docker inspect container_name`

`$ docker inspect -f '{{.Config.Hostname}}' container_name`

`$ docker inspect -f '{{.NetworkSettings.Networks.bridge.IPAddress}}' container_name`

Note: use --format (OR) -f

### 25\. List all container names

`$ docker inspect --format "{{.Name}}" $(docker ps -a -q) | tr -d '/'`

## 2\. STATS:

### 1\. Display usage statistics of a container

`$ docker stats --no-stream container_name`

`$ docker stats --no-stream --all`

`$ docker stats --no-stream --format {{.MemUsage}} container_name`

`$ docker stats --no-stream --format {{.CPUPerc}} container_name`

### 2\. Allocating memory for a container (below command allocates 1 GB RAM)

`$ docker run -it --name container_name -m 1g ubuntu /bin/bash`

`$ docker run -it --name container_name -m 1024m ubuntu /bin/bash`

### 3\. Updating memory of an existing container

`$ docker update -m 2024m container_name`

### 4\. CPU Allocation

`$ docker run -it --cpus="2" --name container_name ubuntu /bin/bash`

`$ docker update --cpus="2" conatiner_name`

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