If I run Docker locally and I bind the containers' ports, I usually connect with them through localhost and not through the dynamically created IP address. I might start a MySQL container, bound with 3306:3306 and can then connect with it to localhost:3306.
If I am using a virtual machine in Windows to run Docker in (e.g. with VirtualBox), the VM has its own interface (e.g. VirtualBox Host-Only Network) which might have an IP address of 192.168.50.1. I can now connect to a MySQL container via 192.168.50.1:3306.
Using a different interface/network for my containers is useful during development because I free up my localhost ports for other things and many browsers treat localhost differently than it does other addresses.
However, Docker Desktop also has advantages over a VM:
Not having to manage the VM
Testcontainers out-of-the-box
Docker Desktop is nice
Should it not be possible to get Docker to bind to ports on a virtual interface instead of localhost, e.g. by creating a Windows virtual switch or even by using the existing VirtualBox network? And is it possible to do this for Docker Desktop (on Windows) for all containers by default?
This answer indicates there's an --ip option available when starting the Docker daemon, but:
Which IP address do I use here? The gateway is the only IP address that I have configured for a virtual switch.
What is the equivalent for Docker Desktop?
When using docker desktop, we would connect to the host machine from the container using the URL 'host.docker.internal'.
however container is not able to connect to the host machine (i.e my machine) when I am using nerdctl instead of docker.
I installed Rancher desktop to use nerdctl
ipconfig getifaddr en0
The above command will give the IP address of your wireless connection. Note, this will only work for MacOS. This IP can then be written to the /etc/hosts of your container against host.docker.internal as they share the same network. This can help the container communicate to the host machine by using host.dock.internal . Although, an elegant solution is expected from RancherDesktop (or its already available in the newer versions).
From lima docs.
The loopback addresses of the host is 192.168.5.2 and is accessible
from the guest as host.lima.internal.
So instead of host.docker.internal, provide 192.168.5.2
I have tested this with nerdctl distributed via Rancher and it works!
reference: https://github.com/lima-vm/lima/blob/master/docs/network.md
I have win 10 as an operating system, I have installed virtualbox where ubuntu is installed and docker with its containers is installed in ubuntu.
I set the virtualbox network in bridge, and in DHCP I assigned an IP that I can easily reach from the win 10 chrome browser (outside of virtualbox). The problem is that I cannot access the docker container where a webserver runs in loalhost, I can access it without problems inside the virtualbox and externally I can access another webserver in the virtualbox but not the webserver docker! How could I solve it?
thanks for any replies!
It seems that I have solved, I describe here the simple solution that I have adopted.
the VM has an IP assigned in dhcp by the bridge network. (this setting has remained for a second webserver to work) In virtualbox settings I simply enabled a second NAT network from "network-settings" and in "advanced-port forwarding" I only added host port on 80 and guest port on 80, because docker run establishes its ip and its port reachable only on local host (in this case reachable only inside virtualbox).
I want to export the complete ip connectivity (UDP and TCP) from a docker container with a Linux app (ie give it's own ip address (in the same subnet as the host), that can be accessed from the host and from other physical machines on the network).
What do I need to configure in Windows, what in docker, what inside the container?
(NB: I don NOT want to expose ports as part of the host).
I finally solved the problem (for me) by installing Ubuntu in Virtual Box and using the docker containers from there. Not the most elegant solution but working on first try.
This question already has answers here:
From inside of a Docker container, how do I connect to the localhost of the machine?
(41 answers)
Closed 12 months ago.
I have a docker container running jenkins. As part of the build process, I need to access a web server that is run locally on the host machine. Is there a way the host web server (which can be configured to run on a port) can be exposed to the jenkins container?
I'm running docker natively on a Linux machine.
UPDATE:
In addition to #larsks answer below, to get the IP address of the Host IP from the host machine, I do the following:
ip addr show docker0 | grep -Po 'inet \K[\d.]+'
For all platforms
Docker v 20.10 and above (since December 14th 2020)
On Linux, add --add-host=host.docker.internal:host-gateway to your Docker command to enable this feature. (See below for Docker Compose configuration.)
Use your internal IP address or connect to the special DNS name host.docker.internal which will resolve to the internal IP address used by the host.
To enable this in Docker Compose on Linux, add the following lines to the container definition:
extra_hosts:
- "host.docker.internal:host-gateway"
For macOS and Windows
Docker v 18.03 and above (since March 21st 2018)
Use your internal IP address or connect to the special DNS name host.docker.internal which will resolve to the internal IP address used by the host.
Linux support pending https://github.com/docker/for-linux/issues/264
MacOS with earlier versions of Docker
Docker for Mac v 17.12 to v 18.02
Same as above but use docker.for.mac.host.internal instead.
Docker for Mac v 17.06 to v 17.11
Same as above but use docker.for.mac.localhost instead.
Docker for Mac 17.05 and below
To access host machine from the docker container you must attach an IP alias to your network interface. You can bind whichever IP you want, just make sure you're not using it to anything else.
sudo ifconfig lo0 alias 123.123.123.123/24
Then make sure that you server is listening to the IP mentioned above or 0.0.0.0. If it's listening on localhost 127.0.0.1 it will not accept the connection.
Then just point your docker container to this IP and you can access the host machine!
To test you can run something like curl -X GET 123.123.123.123:3000 inside the container.
The alias will reset on every reboot so create a start-up script if necessary.
Solution and more documentation here: https://docs.docker.com/docker-for-mac/networking/#use-cases-and-workarounds
When running Docker natively on Linux, you can access host services using the IP address of the docker0 interface. From inside the container, this will be your default route.
For example, on my system:
$ ip addr show docker0
7: docker0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default
link/ether 00:00:00:00:00:00 brd ff:ff:ff:ff:ff:ff
inet 172.17.0.1/16 brd 172.17.255.255 scope global docker0
valid_lft forever preferred_lft forever
inet6 fe80::f4d2:49ff:fedd:28a0/64 scope link
valid_lft forever preferred_lft forever
And inside a container:
# ip route show
default via 172.17.0.1 dev eth0
172.17.0.0/16 dev eth0 src 172.17.0.4
It's fairly easy to extract this IP address using a simple shell
script:
#!/bin/sh
hostip=$(ip route show | awk '/default/ {print $3}')
echo $hostip
You may need to modify the iptables rules on your host to permit
connections from Docker containers. Something like this will do the
trick:
# iptables -A INPUT -i docker0 -j ACCEPT
This would permit access to any ports on the host from Docker
containers. Note that:
iptables rules are ordered, and this rule may or may not do the
right thing depending on what other rules come before it.
you will only be able to access host services that are either (a)
listening on INADDR_ANY (aka 0.0.0.0) or that are explicitly
listening on the docker0 interface.
If you are using Docker on MacOS or Windows 18.03+, you can connect to the magic hostname host.docker.internal.
Lastly, under Linux you can run your container in the host network namespace by setting --net=host; in this case localhost on your host is the same as localhost inside the container, so containerized service will act like non-containerized services and will be accessible without any additional configuration.
Use --net="host" in your docker run command, then localhost in your docker container will point to your docker host.
The answer is...
Replace http://127.0.0.1 or http://localhost with http://host.docker.internal.
Why?
Source in the docs of Docker.
My google search brought me to here, and after digging in the comments I found it's a duplicate of From inside of a Docker container, how do I connect to the localhost of the machine?. I voted for closing this one as a duplicate, but since people (including myself!) often scroll down on the answers rather than reading the comments carefully, here is a short answer.
For linux systems, you can – starting from major version 20.04 of the docker engine – now also communicate with the host via host.docker.internal. This won't work automatically, but you need to provide the following run flag:
--add-host=host.docker.internal:host-gateway
See
https://github.com/moby/moby/pull/40007#issuecomment-578729356
https://github.com/docker/for-linux/issues/264#issuecomment-598864064
Solution with docker-compose:
For accessing to host-based service, you can use network_mode parameter
https://docs.docker.com/compose/compose-file/#network_mode
version: '3'
services:
jenkins:
network_mode: host
EDIT 2020-04-27: recommended for use only in local development environment.
EDIT 2021-09-21: IHaveHandedInMyResignation wrote it does not work for Mac and Windows. Option is supported only for Linux
I created a docker container for doing exactly that https://github.com/qoomon/docker-host
You can then simply use container name dns to access host system e.g.
curl http://dockerhost:9200
Currently the easiest way to do this on Mac and Windows is using host host.docker.internal, that resolves to host machine's IP address. Unfortunately it does not work on linux yet (as of April 2018).
We found that a simpler solution to all this networking junk is to just use the domain socket for the service. If you're trying to connect to the host anyway, just mount the socket as a volume, and you're on your way. For postgresql, this was as simple as:
docker run -v /var/run/postgresql:/var/run/postgresql
Then we just set up our database connection to use the socket instead of network. Literally that easy.
I've explored the various solution and I find this the least hacky solution:
Define a static IP address for the bridge gateway IP.
Add the gateway IP as an extra entry in the extra_hosts directive.
The only downside is if you have multiple networks or projects doing this, you have to ensure that their IP address range do not conflict.
Here is a Docker Compose example:
version: '2.3'
services:
redis:
image: "redis"
extra_hosts:
- "dockerhost:172.20.0.1"
networks:
default:
ipam:
driver: default
config:
- subnet: 172.20.0.0/16
gateway: 172.20.0.1
You can then access ports on the host from inside the container using the hostname "dockerhost".
For docker-compose using bridge networking to create a private network between containers, the accepted solution using docker0 doesn't work because the egress interface from the containers is not docker0, but instead, it's a randomly generated interface id, such as:
$ ifconfig
br-02d7f5ba5a51: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.32.1 netmask 255.255.240.0 broadcast 192.168.47.255
Unfortunately that random id is not predictable and will change each time compose has to recreate the network (e.g. on a host reboot). My solution to this is to create the private network in a known subnet and configure iptables to accept that range:
Compose file snippet:
version: "3.7"
services:
mongodb:
image: mongo:4.2.2
networks:
- mynet
# rest of service config and other services removed for clarity
networks:
mynet:
name: mynet
ipam:
driver: default
config:
- subnet: "192.168.32.0/20"
You can change the subnet if your environment requires it. I arbitrarily selected 192.168.32.0/20 by using docker network inspect to see what was being created by default.
Configure iptables on the host to permit the private subnet as a source:
$ iptables -I INPUT 1 -s 192.168.32.0/20 -j ACCEPT
This is the simplest possible iptables rule. You may wish to add other restrictions, for example by destination port. Don't forget to persist your iptables rules when you're happy they're working.
This approach has the advantage of being repeatable and therefore automatable. I use ansible's template module to deploy my compose file with variable substitution and then use the iptables and shell modules to configure and persist the firewall rules, respectively.
This is an old question and had many answers, but none of those fit well enough to my context. In my case, the containers are very lean and do not contain any of the networking tools necessary to extract the host's ip address from within the container.
Also, usin the --net="host" approach is a very rough approach that is not applicable when one wants to have well isolated network configuration with several containers.
So, my approach is to extract the hosts' address at the host's side, and then pass it to the container with --add-host parameter:
$ docker run --add-host=docker-host:`ip addr show docker0 | grep -Po 'inet \K[\d.]+'` image_name
or, save the host's IP address in an environment variable and use the variable later:
$ DOCKERIP=`ip addr show docker0 | grep -Po 'inet \K[\d.]+'`
$ docker run --add-host=docker-host:$DOCKERIP image_name
And then the docker-host is added to the container's hosts file, and you can use it in your database connection strings or API URLs.
For me (Windows 10, Docker Engine v19.03.8) it was a mix of https://stackoverflow.com/a/43541732/7924573 and https://stackoverflow.com/a/50866007/7924573 .
change the host/ip to host.docker.internal
e.g.: LOGGER_URL = "http://host.docker.internal:8085/log"
set the network_mode to bridge (if you want to maintain the port forwarding; if not use host):
version: '3.7'
services:
server:
build: .
ports:
- "5000:5000"
network_mode: bridge
or alternatively: Use --net="bridge" if you are not using docker-compose (similar to https://stackoverflow.com/a/48806927/7924573)
As pointed out in previous answers: This should only be used in a local development environment.
For more information read: https://docs.docker.com/compose/compose-file/#network_mode and https://docs.docker.com/docker-for-windows/networking/#use-cases-and-workarounds
You can access the local webserver which is running in your host machine in two ways.
Approach 1 with public IP
Use host machine public IP address to access webserver in Jenkins docker container.
Approach 2 with the host network
Use "--net host" to add the Jenkins docker container on the host's network stack. Containers which are deployed on host's stack have entire access to the host interface. You can access local webserver in docker container with a private IP address of the host machine.
NETWORK ID NAME DRIVER SCOPE
b3554ea51ca3 bridge bridge local
2f0d6d6fdd88 host host local
b9c2a4bc23b2 none null local
Start a container with the host network
Eg: docker run --net host -it ubuntu and run ifconfig to list all available network IP addresses which are reachable from docker container.
Eg: I started a nginx server in my local host machine and I am able to access the nginx website URLs from Ubuntu docker container.
docker run --net host -it ubuntu
$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
a604f7af5e36 ubuntu "/bin/bash" 22 seconds ago Up 20 seconds ubuntu_server
Accessing the Nginx web server (running in local host machine) from Ubuntu docker container with private network IP address.
root#linuxkit-025000000001:/# curl 192.168.x.x -I
HTTP/1.1 200 OK
Server: nginx/1.15.10
Date: Tue, 09 Apr 2019 05:12:12 GMT
Content-Type: text/html
Content-Length: 612
Last-Modified: Tue, 26 Mar 2019 14:04:38 GMT
Connection: keep-alive
ETag: "5c9a3176-264"
Accept-Ranges: bytes
In almost 7 years the question was asked, it is either docker has changed, or no one tried this way. So I will include my own answer.
I have found all answers use complex methods. Today, I have needed this, and found 2 very simple ways:
use ipconfig or ifconfig on your host and make note of all IP addresses. At least two of them can be used by the container.
I have a fixed local network address on WiFi LAN Adapter: 192.168.1.101. This could be 10.0.1.101. the result will change depending on your router
I use WSL on windows, and it has its own vEthernet address: 172.19.192.1
use host.docker.internal. Most answers have this or another form of it depending on OS. The name suggests it is now globally used by docker.
A third option is to use WAN address of the machine, or in other words IP given by the service provider. However, this may not work if IP is not static, and requires routing and firewall settings.
PS: Although pretty identical to this question here, and I posted this answer there, I first found this post, so I post it here too as may forget my own answer.
The simplest option that worked for me was,
I used the IP address of my machine on the local network(assigned by the router)
You can find this using the ifconfig command
e.g
ifconfig
en0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
options=400<CHANNEL_IO>
ether f0:18:98:08:74:d4
inet 192.168.178.63 netmask 0xffffff00 broadcast 192.168.178.255
media: autoselect
status: active
and then used the inet address. This worked for me to connect any ports on my machine.
When you have two docker images "already" created and you want to put two containers to communicate with one-another.
For that, you can conveniently run each container with its own --name and use the --link flag to enable communication between them. You do not get this during docker build though.
When you are in a scenario like myself, and it is your
docker build -t "centos7/someApp" someApp/
That breaks when you try to
curl http://172.17.0.1:localPort/fileIWouldLikeToDownload.tar.gz > dump.tar.gz
and you get stuck on "curl/wget" returning no "route to host".
The reason is security that is set in place by docker that by default is banning communication from a container towards the host or other containers running on your host.
This was quite surprising to me, I must say, you would expect the echosystem of docker machines running on a local machine just flawlessly can access each other without too much hurdle.
The explanation for this is described in detail in the following documentation.
http://www.dedoimedo.com/computers/docker-networking.html
Two quick workarounds are given that help you get moving by lowering down the network security.
The simplest alternative is just to turn the firewall off - or allow all. This means running the necessary command, which could be systemctl stop firewalld, iptables -F or equivalent.