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• Docker Machine Ip Default

So, reading through a bunch of blog posts, it seems like with Apple's Big Sur, VMware Fusion is forced to use Apple's DHCP server and can no longer use their build-in DHCP server. As a result, when creating a docker image, using docker-machine the VMware Fusion driver does not return an IP address for the image's MAC address. Docker 'waiting for an IP' when starting or creating new machineHelpful? Please support me on Patreon: thanks & pr. Docker Tip #65: Get Your Docker Host's IP Address from in a Container Once in a while you may need your Docker host's IP address. Here's how to do it on Docker for Mac, Windows and Linux. In Docker Tip #35 I wrote about connecting to your Docker host from inside of a container but a lot of things have changed since then. Here’s a more updated.

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We all know that we can run our application in a packaged environment called container using Docker. When you want containers to talk to each other, the network they create can be assumed to be a bridge network. Run the following command to get a list of networks.

Each network of containers has a subnet mask and can be used to distribute IP addresses to its containers. This also means that each container in the docker network is assigned an IP address. The default subnet for a docker network is 172.17.0.0/16.

Knowing these, we will now see the different methods that can be used to find out the IP address of a docker container in a network.

• Using Docker inspect

Inspect command is used to get low level information about all the running docker containers in the host machine. It is shown in JSON format. We can use the format option with the command to get only a handful of important information.

Use the following commands below to get the container IP address using inspect.

First command is used to get a list of container IDs of all the running containers. This can be used on the second command to find the IP addresses.

• In case of a single container

In case you only have a single container running, you can directly return the last container ID by parsing it

• Using the bash

You can also get a container’s network ID by attaching a bash shell to the container. Use the commands below.

To start the bash of the container, use −

Once you are inside the bash, you can use the following command to access the IP address.

• Exporting the environment variable of the container

For a particular docker container, you can export the environment variable. The following command returns the IP address of the last running container.

• Using the IP address command

You can also access the IP address of the container by running the IP address command. Check out the command below.

• Using the bashrc file

You can access the IP address of a particular container by creating your own custom command. You just need to add a method inside your bashrc file that would take an argument which will be the container ID and then return the IP address of that container. Check out the command below.

Paste the above code at the end of your ∽/.bashrc file.

Reload the file by using the command −

Now, get the container ID using the following command.

Copy the container ID and use it in the following command to get the container’s IP address.

In this article, we have seen six different ways to get a docker container’s IP address. However, the best and probably the easiest one is using the inspect command and this makes it one of the most widely used one too.

Wondering what's the IP address of your running docker container? You can inspect the running container to get that information.

The inspect command gives you many details about the container you are inspecting. Go towards the end and look into the Networks section to get the container's IP address.

You may also use grep command to get just the lines matching the string 'IPAddress'.

Don't be alarmed if your container has more than one IP address. That's not unusual. To understand that, you need to understand how containers communicate with each other.

I'll explain that to you in the next section followed by some other methods of getting the IP address of a running docker container.

How docker containers communicate?

Docker is a tool for packaging and delivering software to the masses using containerization technology. Software can have a multitude of purposes, from possibly simple text processing to a full web server, hosting your private files. Each of these softwares is broken down into microservices and then packaged as containers. Depending on the purpose of the software, one service may need to communicate with another.

For example, consider WordPress. There are two services, one is the web server that serves the frontend, and another is the backend, the database. The frontend has to communicate with the database, otherwise, it just won't work.

This communication is achieved by having at least two network interfaces associated with each of these two containers, both interfaces being connected to the same network. This network is called a 'docker network'.

Docker network

Think of docker network as a pool of available IP addresses. If two containers take on IP addresses from the same pool, they're going to be able to communicate with each other.

There are mainly two types of networks, the default or predefined networks and the user-defined networks.

You can get the list of networks using the following command

Docker-machine Ip Default Does Not Exist

Consider my list below:

Ignore the last two and focus on the first network. The bridge network is the default network every container is going to be connected to if none is specified explicitly. You can get more details about this network by running the docker network inspect bridge command.

I'm going to filter the output since for this demonstration I don't need all the data that inspect is going to explode out.

If you don't have jq installed, please install it using your distribution's package manager.

Each of these docker networks has a subnet, in the case of the bridge network, this subnet is 172.17.0.0/16. This means there are a total of 65,534 - 1 = 65,533 usable hosts or IP addresses. I deducted one since 172.17.0.1 is allocated for the gateway. You can see that as well using the following command

Checking your docker container's IP address

There are a couple of ways you can check the IP address[es] associated with your container, here is a list of all of them including command examples.

Method 1: By inspecting the container

The inspect sub-commands of docker are extremely helpful. A container can be inspected using the docker container inspect [CONTAINER ID]|[CONTAINER NAME] command.

Inspecting a container means getting as much information as possible about the container, from ports, environment variables to mount points, cgroup data, etc. IP address can be extracted from it.

If you run the inspect command on a container, you'll get a bunch of information, in JSON format. Scroll down until you find the key NetworkSettings, there look for the sub-key IPAddress. That's your container's IP address.

The command to execute looks like the following

Here's my output (truncated)

Instead of scrolling through all that, you can filter the output like this:

Here's a filtered output:

If you want to get an IP address associated with a specific network, use a command like the following

A sample output:

method 2: Using the container's shell

This is the most straightforward method, but also something I don't recommend.

In this method, you attach your stdin|stdout with the container's and run the ip command (or some other command that shows the IP addresses associated with the NICs).

The reason I don't recommend this is that many images are quite lightweight, and don't contain the ip command (or something similar).

Take the ubuntu:20.04 image as an example, start a container like the following

To keep the container running I used the sleep 1d command.

Now start a shell process inside the container and attach your stdin|stdout like so

Once you're in this container, try running ip or ifconfig. You'll see something like the following:

To get those commands to work, you need to install the relevant packages. To get ip command, install the iproute2 package and rerun the command as ip a

Now you can see the IP address associated with the card [email protected] being 172.17.0.2.

Notice the network this container is part of. Since I did not create and connect a user-defined network to this container, it was connected to the bridge network, which is why the network of this IP is 172.17.0.0

Docker Machine Ip Windows

This method surely works, although it's more work and not very reproducible, it's intuitive. The next methods should be much better compared to this one.

Docker-machine Ip Not Found

Method 3: By inspecting the network itself

Whenever a container gets connected to a network, that connected container is visible from the network as well, along with the IP address allocated to those containers.

Since my container is connected to the bridge network, I can inspect the network with the following command

Here instead of an id, I'll use the name, bridge

Instead of scrolling down to the Containers section, I'll use jq to filter the output this time.

To demonstrate this, I deployed another container with the name ip. You can see the containers and IP addresses in the above JSON object. Now extracting the IP of a specific container is slightly harder here.

If you know the container id, you can use jq like this

Here's an example

Most of the time you can not remember the container id, so if you want to get the IP from only the container name, you need some knowledge of jq (or just reuse the following command).

Docker Machine Ip Ubuntu

Place the container name in the select function and see the magic happen.

Which method do you prefer? Method 1 probably

Docker Machine Ip Windows 10

Those were all the methods through which you can get the IP address[es] of docker containers. The second method although intuitive isn't reproducible. Most of the time it's the first method that gets used since it's the easiest and gets the job done.

But there may come a time when you'd want to check what some containers are connected to a certain network and get the IP addresses on that network. In that case, inspecting the network and getting the IPs makes sense. You can get all the container names and IPs allocated to them from a network like this

Change bridge to some other network, and you'll get all the containers and their IP addresses like this.

That's it for today. I hope this article was helpful to you. If you have any questions, do let me know in the comments down below.

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