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How To Do SSH Into Docker Container [Step-By-Step Guide]

May 18, 2023

Are you a developer or a sysadmin constantly challenged by the intricacies of container orchestration?💁

Perhaps you’ve found yourself wasting valuable time navigating through countless forums, trying to figure out how to SSH into Docker containers.

The steep learning curve and fragmented documentation make it feel like a time-consuming task that slows your efficiency and hampers productivity.

You’ve probably been there, staring at your command line, frantically typing and retyping commands, only to meet with the dreaded “connection refused” message.

Or worse yet, you finally get access, but it’s to the wrong container! The process can be overwhelming, frustrating, and downright discouraging.

This obstacle makes your day-to-day work stressful and robs you of the time that could be better spent on actual development tasks.

But what if there was an easier way? Imagine a comprehensive guide that simplifies the process of SSHing into Docker containers, a guide that speaks your language and addresses your pain points.

Welcome to the perfect solution – “SSH Into Docker Container: A Comprehensive Guide”. This resource breaks down the process into easy, manageable steps, demystifying the command line, and enabling you to work with Docker containers with increased confidence and efficiency.

Dive in, and in no time, you will be seamlessly SSHing into Docker containers, reclaiming your time, and focusing on what truly matters: innovating and developing stellar applications.

What Will I Learn?💁 show

Using SSH in Conjunction With Docker Containers; Do I Recommend It?

The first question in integrating ssh into docker containers is, is it recommended? Setting up an SSH server within a Docker container is considered a terrible practice, and you should avoid doing so.

However, it’s almost always preferable to utilize the docker exec instruction when getting a shell inside a container.

Docker novices may be tempted to utilize SSH to update files within a container, which is not recommended.

Containers, on the other hand, are intended to be disposable and should be viewed as immutable after formation, except for persistent data stored within volumes. When you make changes to the source code, you should make a new image and relaunch the container.

Aside from the time-consuming configuration process, including adding multiple dependency packages, deploying SSH in a Docker image introduces another possible attack vector.

Managing several autonomous SSH processes on a network of interconnected active containers requires you to remember the right connection for each carrier on a system with many active containers.

As an alternative to installing SSH on every container, run it only once on the physical machine hosting Docker.

Then, access your host via SSH and execute docker exec -it my-container bash to enter individual containers using the docker command.

Although docker exec is the primary way, there are several situations in which SSH may be helpful. For example, you may use it as a stopgap method to interact with legacy deployment platforms while developing a more permanent solution.

Some integrated development environments (IDEs) and build systems may also take advantage of it to enable live reload capabilities while creating.

How to Configure SSH into Docker Container

Let’s discuss how to set up an ssh server on Windows using the Docker desktop application.

If you don’t already have docker desktop for Windows or the windows subsystem for Linux installed, you can go ahead and start the installation process now.

The first thing you’ll need to do is install Docker on your computer or laptop. Once the docker desktop is installed, everything is running and configured to be accessed through an actual Ubuntu 20.04 Linux subsystem setup; you should be ready to start working on your projects.

If you don’t have Ubuntu already downloaded, issue the command.

Now, enter the command docker images to see if you have the latest ubuntu image.

docker images

How to Start the Docker Container

To begin, you must run a docker container. When the container exits, remove it from your system to ensure it is no longer present. Then, using the terminal, start up the docker container in interactive mode to see what is going on.

You have the opportunity to accomplish something unique here. First, assign the localhost to port 8022 from the localhost to the actual docker container by using the localhost to port 8022 commands. Then, for convenience, give the Docker container a name.

Run the latest version of Ubuntu and run bash on startup.

Here is the command you should enter:

docker run -- rm -it -p 8022:8022 --name sshd ubuntu: latest bash

After you’ve entered everything, press enter, you should receive a prompt, and then you should be ready to go.

Clearing the screen is the first thing you should do before proceeding with the process.

How to Install the Necessary Software Packages in SSH Into Docker Container

To install the software package, the very first thing you should do is enter the app-get update.

app-get update

If you’re not on a container, you might need to use sudo. So you’ll put in sudo, and then you’ll put your root password in, or you can sudo su first, and then you can issue all the commands as root.

But on the docker container, we’re going to be utilizing root.

When the update is done, you can clear the screen. Then, you can proceed to do an app get now on a non-docker system. Then you would need to put in a -y so you’re not prompted to say yes to install things every time.

Go ahead and install the open ssh server, and you would install vim so that you have an editor to use.

You can also install nano here if you want. But you would be installing ssh as well. You could choose to install the uncomplicated firewall as well.
With that done, you hit enter.

apt-get -y install openssh-server vim ssh ufw

Expect to wait for a little as it takes a while to get done. You would return to the setup during the installation because it would ask you a couple of questions.

It would ask for a geographic area, so go on and choose your geographic location. In this example, we put America.

How To Do SSH Into Docker Container [Step-By-Step Guide]

We also choose New York, so we select 105 for the time zone.

This completes the installation successfully. So go ahead and clear the screen. The next thing that we are going to do is update our ssh’s configuration not to utilize the commonly known port 22 that ssh runs on.

How to Set up SSH Port Access

The next step in integrating ssh into docker container would be setting up SSH port access.

We will put it on an upper-level port above 1024 for security purposes. So the way you do that is you’re going to use vi you can use nano which we installed initially. Then you’re going to go to the ssh update ssh d underscore config file.

vi /etc/ssh/sshd_config

Come down to this port here, open it up and port as shown in the figure below.

Then input 8022 instead. You can make use of any port above 1024. Just ensure that it does not conflict with other services you have already configured.

Go ahead and save the file and clear the screen.

The next thing you’ll want to do is open up port 8022; we had ported from our local system to the container when we started up this container.

Setting up Firewall Services

To set up firewall services when integrating ssh into docker container, go ahead and open that up this firewall; here, we will do an uncomplicated firewall.

You are going to key in, allow 8022.

allow 8022

You will see that the rule has been updated, and we’re good to go. So the next thing you should do is to clear the screen.

How to Start Up the SSH Service

To start up the ssh service when working with ssh into docker container,

You are going to do a system or enable it. You’re going to do a system ‘ctl enable ssh.’ Once that’s complete, you’ll do a system ctl start ssh. You could get an error saying you need to use the init system.

So instead, you’ll do a slash etsy inet.d ssh start, and there, you’ll have the ssh started.

How to Create Private and Public Keys

Now let us create the ssh keys operating with ssh into docker container. The public key takes place on the server, and the private key to put on our clients.

We do this by typing in ssh keygen, and we’re going to add a bit size of 4096 to keep it nice and secure.

ssh-keygen - 4096

Now it will ask you what you want to call the file. In this example, let’s keep it at default as id_rsa; it will ask for a passphrase we will put in a passphrase. So let’s just put a nice simple one and confirm it, and that’s it, we are done.

Please use a complex passphrase for proper security. We chose a simple passphrase for the purpose of the example.

We now have an rs8 key that is 4096 bits, nice and secure. So let’s now go ahead and display with a cat from the home directory ssh, with that rsa key that we just created.

cat~/ .ssh/id_rsa

We would grab this entire file

and copy it to the clipboard dragging it over the desktop. You are going to right-click and do a new text file.

Let’s call it private key. When we open it up, we will paste in that private key.

We would make sure that we have the end comment down here with the dashes and the beginning comment at the top with the dashes. We’re all good there. Now we are going to save the file.

You can close this out and move the clipboard away. Clear the screen to make it nice and clean.

How to Add Public Key to the Authorized Keys File

The next question we will answer in our integrating ssh into docker containers guide is how to add a public key to the authorized key files.

What we want to do now from our local directory ssh; you would cut out rsa.hub file and pipe it into authorized keys.

cat ~/ .ssh/_rsa.pub > ~/ .ssh/authorized_keys

Note: I did not have an authorized key file since I was on a brand new installation. However, if you are not on a new system, do not use the single ‘>’; instead, use the double angle bracket ‘>>’ to append the to the authorized key file.

cat ~/ .ssh/_rsa.pub >> ~/ .ssh/authorized_keys

How to Install Putty

The next thing we need to do because we’re on a windows system is download putty. Since we’re on windows, we’re going to have to do a little manipulation to our private key to get this to work and be able to access our ubuntu server that’s running the ssh daemon.

So, we begin by opening up Google and typing in putty download for Windows. It would be best if you chose it and then downloaded putty.

The next step is for you to grab it from here, and the best bet is, first of all, since we’re running ubuntu 2004, you need to be at the latest version. So let’s download the 64-bit MSI file in our case.

Run it through a quick check for viruses and malware, and you will be ready to install it. Then go ahead and grab the MSI file, go through the install process, and install it.

How to Create Windows for .PPK File

The last question we would be answering in this integrating ssh into docker containers guide is how do we create Windows for our .ppk file.

Under your start menu, you should find all the different putty elements. You can put them on your desktop just for ease.

The first one you want to open up is the puttygen double click on it. We would then open up and load our private key file, so if we go and look for that private key file, we’ll see that there’s nothing in there. So you need first to set this to all files to find it.

Grab the private key and open it up.

It’s going to ask you for that password. Then, type in the passphrase you created. It would have all of your information.

You should save that private key. You can give it the same name we gave the private key, but there will be no extension instead.

SSH into Docker container from Mac:-

Here’s how you can SSH into a Docker container from a Mac:

Step 1:- Open a terminal window on your Mac.

Step 2:- Use the “docker ps” command to list all running Docker containers and find the container you want to SSH into.

Step 3:- Copy the container ID or name.

Step 4:- Use the “docker inspect” command followed by the container ID or name to get the container’s IP address.

Step 5:- Use the “ssh” command followed by the IP address to connect to the container. For example, “ssh user@container-ip”.

Step 6:- If prompted, enter the password for the user account on the container.

Step 7:- Once connected, you can run commands inside the container using the terminal as if you were directly logged into the container.

📗FAQ

Is it possible to SSH into a Docker container?

Yes, it is possible to SSH into a Docker container by installing an SSH server inside the container and mapping the container’s SSH port to a port on the host machine.

How to SSH into a remote Docker container?

To SSH into a remote Docker container, you need SSH access to the remote machine where the container is running. Once you have SSH access, you can use the SSH command to connect to the container by specifying the container’s IP address or hostname.

How to access the container via SSH?

You can access a container via SSH by installing an SSH server inside the container and then mapping the container’s SSH port to a port on the host machine. Once you have done that, you can use the SSH command to connect to the container by specifying the mapped port on the host machine.

How to mount SSH keys in a Docker container?

To mount SSH keys in a Docker container, you can use the “-v” option with the “docker run” command to mount a directory containing the SSH keys into the container. You can then use the keys to SSH into the container from the host machine.

How do I connect to a Docker container?

You can connect to a Docker container using the “docker exec” command. This command allows you to run commands inside a running container, including starting a new shell session.

How to bash into a Docker container?

To bash into a Docker container, you can use the “docker exec” command with the “-it” options, followed by the container ID or name and the command “bash”. This will start a new shell session inside the container.

How do I access a Docker container from outside the network?

To access a Docker container from outside the network, you must expose the container’s ports to the host machine and then configure port forwarding on the router to forward traffic to the host machine’s IP address.

How to remotely deploy a Docker container?

To remotely deploy a Docker container, you can use tools like Docker Compose, Kubernetes, or a cloud platform like AWS, Azure, or GCP. These tools allow you to manage and deploy Docker containers remotely.

How do you expose port 22 in a Docker container?

To expose port 22 in a Docker container, you can use the “-p” option with the “docker run” command to map port 22 inside the container to a port on the host machine. For example, “-p 2222:22” maps port 22 inside the container to port 2222 on the host machine.

How to send commands to a Docker container?

To send commands to a Docker container, you can use the “docker exec” command with the container ID or name and the command you want to run inside the container. For example, “docker exec my-container ls” will run the “ls” command inside the “my-container” container.

How do I access a container by console?

To access a container by console, you can use the “docker exec” command with the “-it” options, followed by the container ID or name and the command you want to run inside the container.

For example, “docker exec -it my-container bash” will start a new shell session inside the “my-container” container.

How to access SSH remotely?

You need SSH access to the remote machine where the SSH server is running to access SSH remotely. Once you have SSH access, you can use the SSH command to connect to the server from any machine that has access to the remote network.

How to mount files into a Docker container?

To mount files into a Docker container, you can use the “-v” option with the “docker run” command to mount a directory from the host machine into the container.

For example, “-v /host/dir:/container/dir” will mount the “/host/dir” directory on the host machine into the “/container/dir” directory inside the container.

How to deploy SSH key?

To deploy an SSH key, you can copy the public key to the authorized_keys file on the remote machine where the SSH server is running.

You can also mount the SSH key directory inside a Docker container using the “-v” option and use the keys to SSH into the container from the host machine.

What IP address to connect to a Docker container?

To connect to a Docker container, you can use the container’s IP address or hostname, obtained using the “docker inspect” command.

Alternatively, you can map the container’s ports to a port on the host machine and use the host machine’s IP address to connect to the container.

How do I open a port in a Docker container?

To open a port in a Docker container, you can use the “-p” option with the “docker run” command to map the container’s port to a port on the host machine. For example, “-p 8080:80” maps port 80 inside the container to port 8080 on the host machine.

Does a Docker container have an IP address?

Yes, a Docker container has an IP address, which can be obtained using the “docker inspect” command. By default, Docker containers are assigned a random IP address from the bridge network, but you can also assign a specific IP address using the “–ip” option with the “docker run” command.

How do I access a local Docker container?

To access a local Docker container, you can use the container’s IP address or hostname, which can be obtained using the “docker inspect” command.

Alternatively, you can map the container’s ports to a port on the host machine and use “localhost” or “127.0.0.1” to connect to the container.

How to login into a Docker container as root?

To login into a Docker container as root, you can use the “docker exec” command with the “-u” option and the user ID of the root user, which is usually “0”. For example, “docker exec -u 0 my-container bash” will start a new shell session inside the “my-container” container as root.

How to access a Docker container from a browser?

To access a Docker container from a browser, you can map the container’s ports to a port on the host machine and then use the host machine’s IP address or hostname followed by the mapped port to access the container from the browser.

How do I access a container remotely?

To access a container remotely, you need SSH access to the remote machine where the container is running. Once you have SSH access, you can use the “docker exec” command to connect to the container and run commands inside it.

How to access Docker container IP from a host?

To access a Docker container IP from the host machine, you can use the “docker inspect” command to obtain the container’s IP address and then use the IP address to connect to the container from the host machine.

How to deploy a Docker container locally?

To deploy a Docker container locally, you can use the “docker run” command to start a new container on the local machine. You can also use tools like Docker Compose or Kubernetes to manage multiple containers and their dependencies locally.

Do I need to expose ports in Docker?

Yes, you need to expose ports in Docker if you want to access a container’s services from outside the container, either from the host machine or other machines on the network.

How do I expose a container to a host port?

To expose a container to a host port, you can use the “-p” option with the “docker run” command to map the container’s port to a port on the host machine. For example, “-p 8080:80” maps port 80 inside the container to port 8080 on the host machine.

Can a Docker container expose two ports?

Yes, a Docker container can expose multiple ports by using multiple “-p” options with the “docker run” command. For example, “-p 8080:80 -p 8443:443” maps port 80 and port 443 inside the container to port 8080 and port 8443 on the host machine, respectively.

How to communicate the Docker container with a host?

To communicate a Docker container with the host machine, you can map the container’s ports to a port on the host machine and then use the host machine’s IP address or hostname followed by the mapped port to communicate with the container.

What command transfers files from host to Docker container?

To transfer files from the host machine to a Docker container, you can use the “docker cp” command. For example, “docker cp file.txt my-container:/dir/file.txt” copies the “file.txt” file from the host machine to the “/dir” directory inside the “my-container” container.

What is the command to view container?

To view information about a Docker container, you can use the “docker inspect” command followed by the container ID or name. This command displays detailed information about the container, including its IP address, port mappings, environment variables, and more.

How to send SSH commands remotely?

To send SSH commands remotely, you need to have SSH access to the remote machine where the SSH server is running. Once you have SSH access, you can use the SSH command to connect to the server and run commands remotely.

How to access SSH from command prompt?

To access SSH from the command prompt, you can use the SSH command followed by the username and hostname or IP address of the remote machine. For example, “ssh user@remote-host” connects to the “remote-host” machine as the “user” user.

What is SSH terminal?

SSH terminal is a command-line interface that allows you to connect to a remote machine over SSH and run commands remotely. It provides a secure way to access and manage remote servers and containers.

How to access Docker container VS Code?

To access a Docker container in VS Code, you can use the “Remote – Containers” extension, which allows you to develop inside a container using VS Code. This extension provides a seamless integration with Docker and allows you to use all the features of VS Code, including debugging, IntelliSense, and more, inside the container.

Final Thoughts

So, we’ve journeyed through the realm of SSHing into Docker containers, breaking down complexities and turning them into manageable steps.

You’ve seen firsthand that what once felt like an uphill battle can be transformed into an efficient and streamlined process.

However, remember that this isn’t the end of your learning journey. Docker, like any other technology, is continuously evolving and enhancing.

Staying updated and regularly brushing up your skills will help you keep up with these changes, ensuring you’re always at the top of your game.

By following the strategies outlined in this comprehensive guide, you’ll have conquered the fear of the command line and the confusion around Docker containers.

No more will you be held back by the technicalities of SSHing into Docker containers. Instead, you’re now equipped to tap into the full potential of Docker, leading to an enriched development experience and enhanced productivity.

So go ahead, apply what you’ve learned, and watch as the world of Docker becomes less daunting and more like a playground for your development tasks.

Remember, in technology, the best way to learn is by doing. SSH into your Docker containers confidently, and make the most of your time, skills, and innovation. You are now truly the master of your Docker domain.