On my windows laptop I have created a Play application which runs fine if I execute its scripts directly. On the local machine, I access the application using localhost:9000 URL.
I have now created a Docker image of the application and have exposed port 9000
#this docker file copies prod specific files to container, eg logback_prod.xml and application_prod.conf
FROM openjdk:8
#ENV APP_NAME myapp
#ENV APP_VERSION 1.0-SNAPSHOT
...
#entrypoint is deploy/....
EXPOSE 9000
ENTRYPOINT ...
But I can't access the application on localhost:9000. I suspect that the image might be running on some other IP created by docker itself.
Am I correct? How can I access my application through the container? I don't need Kubernetes Services etc. as I already have that setup on another machine. My specific question is how to access the docker container directly.
UPDATE
I also tried running the docker image using --network="host" but that doesn't work either
UPDATE 2
Based on the suggestions below, I executed the following commands but still can't access the application.
docker run -p 9000:9000 --env-file env.txt imagename
I see the trace
[debug] a.i.TcpListener - Successfully bound to /0.0.0.0:9000
[info] p.c.s.AkkaHttpServer - Listening for HTTP on /0.0.0.0:9000
docker ps -a shows application is up with port binding 0.0.0.0:9000->9000/tcp
docker inspect shows IP - "IPAddress": "172.17.0.2"
but http://172.17.0.2:9000/ on Chrome doesn't work This site can’t be reached172.17.0.2
netstat -ab on cmd shows TCP 0.0.0.0:9000 LAPTOP-788I0GL1:0 LISTENING [com.docker.backend.exe]
Identify container's IP Address
Try these options with a running container.
<docker> refers to container's name or id
docker inspect --format '{{ .NetworkSettings.IPAddress }}' <docker>
//WINDOWS ONLY
docker inspect --format "{{ .NetworkSettings.IPAddress }}" <docker>
docker inspect <docker> | grep "IPAddress"
Grep not avaliable on Windows*
docker network inspect bridge
This last one would output all running containers' info that are allocated in the bridge network (default). Once identified, check the container's IPv4Address field.
Expose ports
In order to be able to connect to the a container's port, you could expose it. Note that the previous step is not needed in this case:
docker run -p 9000:9000 --env-file env.txt manuchadha25/mydockerimage
By default the docker will bind/listen to all interfaces on the host. The -p 9000:9000 option exposes the port, and as a result you get: 0.0.0.0:9000->9000/tcp
Now localhost:9000 succesfully connects to your docker process.
You can try the command docker inspect:
docker inspect <containerid>
for list the containers ids you can run the command:
docker ps
In order to get the ipAddress information you should look to node:
"IPAddress": "172.23.0.2"
In the json output produced.
Here is the documentation for docker inspect command.
I have a very special scenario. A virtual machine containing some docker containers. One of this containers needs to know the host ip. The problem is if I pass the host ip on container build or using -e on docker run command, it remains "static" (always the same, the one of that moment) on the container.
That vm can be on a laptop and the laptop is moving from different networks and the vm host ip can be different each reboot.
This special container has the --restart=always and is not built or "docker run" again... only once. And as I said, I need the host's ip on each reboot to configure the service inside the container on it's entrypoint because the container has a bind dns server which must load a zone with some dns entries that must be pointing to itself (the host's ip). An environment var would be great if possible. These are my data:
The "normal" lauch
The end of my Dockerfile:
....
....
ENTRYPOINT ["/etc/bind/entrypoint.sh"]
CMD ["/usr/sbin/named", "-g", "-c", "/etc/bind/named.conf", "-u", "bind"]
Entrypoint file (the regex works fine if the var could have the right value):
#!/bin/bash
sed -ri "s/IN A.*/IN A $HOSTIP/" /etc/bind/db.my.zone
exec "$#"
Docker run cmd:
docker run --name myContainer -d --restart=always -p 53:53 -p 53:53/udp myImage
What I tried:
I guess the entrypoint is ok and shouldn't be modified if I can provide to it a var with the right value.
If I put a -e on docker run command, it is "hardcoded" forever with the same ip always even if the host is on different networks:
docker run -e HOSTIP=$(ifconfig eth0 | grep netmask | awk '{print $2}') --name myContainer \
-d --restart=always -p 53:53 -p 53:53/udp myImage
I tried unsuccessfully also modifying the CMD on Dockerfile:
CMD (export HOSTIP=$(ifconfig eth0 | grep netmask | awk '{print $2}'));/usr/sbin/named -g -c /etc/bind/named.conf -u bind
Is possible to achieve something like this? Thanks.
There is the file /proc/net/tcp on the host machine that shows all the opened sockets. In particular, the second column is the local_address of the host interface.
The values in this column are store as little-endian four-byte hexadecimal numbers. To convert these to IP addresses take a look here
Thus when starting you container, you can mount this file from the host onto the container -v /proc/net/tcp:/host-tcp and read the host ip addresses which will be constantly reflected in this file.
I finally solved it. Thank you #yamenk for your answer, it gave me the idea, upvoting.
Finally what I did:
I created a simple script on host which is getting host ip and writting it into another file.
I set that script to be launched on every host boot before docker start.
I mapped the file with the ip into the container using -v on docker run command.
I set my entrypoint to get the ip from that file containing the ip and modifying with sed the needed container config files
Everything working! if I boot the vm (the host machine) on another different network, it gets the ip and the container is able to reconfigure itself before starting with the new ip.
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 10 months ago.
As the title says, I need to be able to retrieve the IP address the docker hosts and the portmaps from the host to the container, and doing that inside of the container.
/sbin/ip route|awk '/default/ { print $3 }'
As #MichaelNeale noticed, there is no sense to use this method in Dockerfile (except when we need this IP during build time only), because this IP will be hardcoded during build time.
As of version 18.03, you can use host.docker.internal as the host's IP.
Works in Docker for Mac, Docker for Windows, and perhaps other platforms as well.
This is an update from the Mac-specific docker.for.mac.localhost, available since version 17.06, and docker.for.mac.host.internal, available since version 17.12, which may also still work on that platform.
Note, as in the Mac and Windows documentation, this is for development purposes only.
For example, I have environment variables set on my host:
MONGO_SERVER=host.docker.internal
In my docker-compose.yml file, I have this:
version: '3'
services:
api:
build: ./api
volumes:
- ./api:/usr/src/app:ro
ports:
- "8000"
environment:
- MONGO_SERVER
command: /usr/local/bin/gunicorn -c /usr/src/app/gunicorn_config.py -w 1 -b :8000 wsgi
Update: On Docker for Mac, as of version 18.03, you can use host.docker.internal as the host's IP. See aljabear's answer. For prior versions of Docker for Mac the following answer may still be useful:
On Docker for Mac the docker0 bridge does not exist, so other answers here may not work. All outgoing traffic however, is routed through your parent host, so as long as you try to connect to an IP it recognizes as itself (and the docker container doesn't think is itself) you should be able to connect. For example if you run this from the parent machine run:
ipconfig getifaddr en0
This should show you the IP of your Mac on its current network and your docker container should be able to connect to this address as well. This is of course a pain if this IP address ever changes, but you can add a custom loopback IP to your Mac that the container doesn't think is itself by doing something like this on the parent machine:
sudo ifconfig lo0 alias 192.168.46.49
You can then test the connection from within the docker container with telnet. In my case I wanted to connect to a remote xdebug server:
telnet 192.168.46.49 9000
Now when traffic comes into your Mac addressed for 192.168.46.49 (and all the traffic leaving your container does go through your Mac) your Mac will assume that IP is itself. When you are finish using this IP, you can remove the loopback alias like this:
sudo ifconfig lo0 -alias 192.168.46.49
One thing to be careful about is that the docker container won't send traffic to the parent host if it thinks the traffic's destination is itself. So check the loopback interface inside the container if you have trouble:
sudo ip addr show lo
In my case, this showed inet 127.0.0.1/8 which means I couldn't use any IPs in the 127.* range. That's why I used 192.168.* in the example above. Make sure the IP you use doesn't conflict with something on your own network.
AFAIK, in the case of Docker for Linux (standard distribution), the IP address of the host will always be 172.17.0.1 (on the main network of docker, see comments to learn more).
The easiest way to get it is via ifconfig (interface docker0) from the host:
ifconfig
From inside a docker, the following command from a docker: ip -4 route show default | cut -d" " -f3
You can run it quickly in a docker with the following command line:
# 1. Run an ubuntu docker
# 2. Updates dependencies (quietly)
# 3. Install ip package (quietly)
# 4. Shows (nicely) the ip of the host
# 5. Removes the docker (thanks to `--rm` arg)
docker run -it --rm ubuntu:22.04 bash -c "apt-get update > /dev/null && apt-get install iproute2 -y > /dev/null && ip -4 route show default | cut -d' ' -f3"
For those running Docker in AWS, the instance meta-data for the host is still available from inside the container.
curl http://169.254.169.254/latest/meta-data/local-ipv4
For example:
$ docker run alpine /bin/sh -c "apk update ; apk add curl ; curl -s http://169.254.169.254/latest/meta-data/local-ipv4 ; echo"
fetch http://dl-cdn.alpinelinux.org/alpine/v3.3/main/x86_64/APKINDEX.tar.gz
fetch http://dl-cdn.alpinelinux.org/alpine/v3.3/community/x86_64/APKINDEX.tar.gz
v3.3.1-119-gb247c0a [http://dl-cdn.alpinelinux.org/alpine/v3.3/main]
v3.3.1-59-g48b0368 [http://dl-cdn.alpinelinux.org/alpine/v3.3/community]
OK: 5855 distinct packages available
(1/4) Installing openssl (1.0.2g-r0)
(2/4) Installing ca-certificates (20160104-r2)
(3/4) Installing libssh2 (1.6.0-r1)
(4/4) Installing curl (7.47.0-r0)
Executing busybox-1.24.1-r7.trigger
Executing ca-certificates-20160104-r2.trigger
OK: 7 MiB in 15 packages
172.31.27.238
$ ifconfig eth0 | grep -oP 'inet addr:\K\S+'
172.31.27.238
The only way is passing the host information as environment when you create a container
run --env <key>=<value>
The --add-host could be a more cleaner solution (but without the port part, only the host can be handled with this solution). So, in your docker run command, do something like:
docker run --add-host dockerhost:`/sbin/ip route|awk '/default/ { print $3}'` [my container]
(From https://stackoverflow.com/a/26864854/127400 )
docker network inspect bridge -f '{{range .IPAM.Config}}{{.Gateway}}{{end}}'
It's possible to retrieve it using docker network inspect
The standard best practice for most apps looking to do this automatically is: you don't. Instead you have the person running the container inject an external hostname/ip address as configuration, e.g. as an environment variable or config file. Allowing the user to inject this gives you the most portable design.
Why would this be so difficult? Because containers will, by design, isolate the application from the host environment. The network is namespaced to just that container by default, and details of the host are protected from the process running inside the container which may not be fully trusted.
There are different options depending on your specific situation:
If your container is running with host networking, then you can look at the routing table on the host directly to see the default route out. From this question the following works for me e.g.:
ip route get 1 | sed -n 's/^.*src \([0-9.]*\) .*$/\1/p'
An example showing this with host networking in a container looks like:
docker run --rm --net host busybox /bin/sh -c \
"ip route get 1 | sed -n 's/^.*src \([0-9.]*\) .*$/\1/p'"
For current versions of Docker Desktop, they injected a DNS entry into the embedded VM:
getent hosts host.docker.internal | awk '{print $1}'
With the 20.10 release, the host.docker.internal alias can also work on Linux if you run your containers with an extra option:
docker run --add-host host.docker.internal:host-gateway ...
If you are running in a cloud environment, you can check the metadata service from the cloud provider, e.g. the AWS one:
curl http://169.254.169.254/latest/meta-data/local-ipv4
If you want your external/internet address, you can query a remote service like:
curl ifconfig.co
Each of these have limitations and only work in specific scenarios. The most portable option is still to run your container with the IP address injected as a configuration, e.g. here's an option running the earlier ip command on the host and injecting it as an environment variable:
export HOST_IP=$(ip route get 1 | sed -n 's/^.*src \([0-9.]*\) .*$/\1/p')
docker run --rm -e HOST_IP busybox printenv HOST_IP
TLDR for Mac and Windows
docker run -it --rm alpine nslookup host.docker.internal
... prints the host's IP address ...
nslookup: can't resolve '(null)': Name does not resolve
Name: host.docker.internal
Address 1: 192.168.65.2
Details
On Mac and Windows, you can use the special DNS name host.docker.internal.
The host has a changing IP address (or none if you have no network access). From 18.03 onwards our recommendation is to connect to the special DNS name host.docker.internal, which resolves to the internal IP address used by the host. This is for development purpose and will not work in a production environment outside of Docker Desktop for Mac.
If you want real IP address (not a bridge IP) on Windows and you have docker 18.03 (or more recent) do the following:
Run bash on container from host where image name is nginx (works on Alpine Linux distribution):
docker run -it nginx /bin/ash
Then run inside container
/ # nslookup host.docker.internal
Name: host.docker.internal
Address 1: 192.168.65.2
192.168.65.2 is the host's IP - not the bridge IP like in spinus accepted answer.
I am using here host.docker.internal:
The host has a changing IP address (or none if you have no network access). From 18.03 onwards our recommendation is to connect to the special DNS name host.docker.internal, which resolves to the internal IP address used by the host. This is for development purpose and will not work in a production environment outside of Docker for Windows.
In linux you can run
HOST_IP=`hostname -I | awk '{print $1}'`
In macOS your host machine is not the Docker host. Docker will install it's host OS in VirtualBox.
HOST_IP=`docker run busybox ping -c 1 docker.for.mac.localhost | awk 'FNR==2 {print $4}' | sed s'/.$//'`
I have Ubuntu 16.03. For me
docker run --add-host dockerhost:`/sbin/ip route|awk '/default/ { print $3}'` [image]
does NOT work (wrong ip was generating)
My working solution was that:
docker run --add-host dockerhost:`docker network inspect --format='{{range .IPAM.Config}}{{.Gateway}}{{end}}' bridge` [image]
Docker for Mac
I want to connect from a container to a service on the host
The host has a changing IP address (or none if you have no network access). From 18.03 onwards our recommendation is to connect to the special DNS name host.docker.internal, which resolves to the internal IP address used by the host.
The gateway is also reachable as gateway.docker.internal.
https://docs.docker.com/docker-for-mac/networking/#use-cases-and-workarounds
If you enabled the docker remote API (via -Htcp://0.0.0.0:4243 for instance) and know the host machine's hostname or IP address this can be done with a lot of bash.
Within my container's user's bashrc:
export hostIP=$(ip r | awk '/default/{print $3}')
export containerID=$(awk -F/ '/docker/{print $NF;exit;}' /proc/self/cgroup)
export proxyPort=$(
curl -s http://$hostIP:4243/containers/$containerID/json |
node -pe 'JSON.parse(require("fs").readFileSync("/dev/stdin").toString()).NetworkSettings.Ports["DESIRED_PORT/tcp"][0].HostPort'
)
The second line grabs the container ID from your local /proc/self/cgroup file.
Third line curls out to the host machine (assuming you're using 4243 as docker's port) then uses node to parse the returned JSON for the DESIRED_PORT.
My solution:
docker run --net=host
then in docker container:
hostname -I | awk '{print $1}'
Here is another option for those running Docker in AWS. This option avoids having using apk to add the curl package and saves the precious 7mb of space. Use the built-in wget (part of the monolithic BusyBox binary):
wget -q -O - http://169.254.169.254/latest/meta-data/local-ipv4
use hostname -I command on the terminal
Try this:
docker run --rm -i --net=host alpine ifconfig
So... if you are running your containers using a Rancher server, Rancher v1.6 (not sure if 2.0 has this) containers have access to http://rancher-metadata/ which has a lot of useful information.
From inside the container the IP address can be found here:
curl http://rancher-metadata/latest/self/host/agent_ip
For more details see:
https://rancher.com/docs/rancher/v1.6/en/rancher-services/metadata-service/
This is a minimalistic implementation in Node.js for who is running the host on AWS EC2 instances, using the afore mentioned EC2 Metadata instance
const cp = require('child_process');
const ec2 = function (callback) {
const URL = 'http://169.254.169.254/latest/meta-data/local-ipv4';
// we make it silent and timeout to 1 sec
const args = [URL, '-s', '--max-time', '1'];
const opts = {};
cp.execFile('curl', args, opts, (error, stdout) => {
if (error) return callback(new Error('ec2 ip error'));
else return callback(null, stdout);
})
.on('error', (error) => callback(new Error('ec2 ip error')));
}//ec2
and used as
ec2(function(err, ip) {
if(err) console.log(err)
else console.log(ip);
})
If you are running a Windows container on a Service Fabric cluster, the host's IP address is available via the environment variable Fabric_NodeIPOrFQDN. Service Fabric environment variables
Here is how I do it. In this case, it adds a hosts entry into /etc/hosts within the docker image pointing taurus-host to my local machine IP: :
TAURUS_HOST=`ipconfig getifaddr en0`
docker run -it --rm -e MY_ENVIRONMENT='local' --add-host "taurus-host:${TAURUS_HOST}" ...
Then, from within Docker container, script can use host name taurus-host to get out to my local machine which hosts the docker container.
Maybe the container I've created is useful as well https://github.com/qoomon/docker-host
You can simply use container name dns to access host system e.g. curl http://dockerhost:9200, so no need to hassle with any IP address.
The solution I use is based on a "server" that returns the external address of the Docker host when it receives a http request.
On the "server":
1) Start jwilder/nginx-proxy
# docker run -d -p <external server port>:80 -v /var/run/docker.sock:/tmp/docker.sock:ro jwilder/nginx-proxy
2) Start ipify container
# docker run -e VIRTUAL_HOST=<external server name/address> --detach --name ipify osixia/ipify-api:0.1.0
Now when a container sends a http request to the server, e.g.
# curl http://<external server name/address>:<external server port>
the IP address of the Docker host is returned by ipify via http header "X-Forwarded-For"
Example (ipify server has name "ipify.example.com" and runs on port 80, docker host has IP 10.20.30.40):
# docker run -d -p 80:80 -v /var/run/docker.sock:/tmp/docker.sock:ro jwilder/nginx-proxy
# docker run -e VIRTUAL_HOST=ipify.example.com --detach --name ipify osixia/ipify-api:0.1.0
Inside the container you can now call:
# curl http://ipify.example.com
10.20.30.40
On Ubuntu, hostname command can be used with the following options:
-i, --ip-address addresses for the host name
-I, --all-ip-addresses all addresses for the host
For example:
$ hostname -i
172.17.0.2
To assign to the variable, the following one-liner can be used:
IP=$(hostname -i)
Another approach is based on traceroute and it's working on a Linux host for me, e.g. in a container based on Alpine:
traceroute -n 8.8.8.8 -m 4 -w 1 | awk '$1~/\d/&&$2!~/^172\./{print$2}' | head -1
It takes a moment, but lists the first hop's IP that does not start with 172. If there is no successful response, try increasing the limit on the tested hops using -m 4 argument.
With https://docs.docker.com/machine/install-machine/
a) $ docker-machine ip
b) Get the IP address of one or more machines.
$ docker-machine ip host_name
$ docker-machine ip host_name1 host_name2