How to get the IP address of the docker host from inside a docker container

Question

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

User · Answer

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);
    })

User · Answer

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

User · Answer

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

User · Answer

Try this  docker run --rm -i --net host alpine ifconfig

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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        -  quot 8000 quot      environment        - MONGO SERVER     command   usr local bin gunicorn -c  usr src app gunicorn config py -w 1 -b  8000 wsgi

User · Answer

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

User · Answer

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

User · Answer

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 quot   quot  -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 20 10 bash -c  quot apt-get update  gt   dev null  amp  amp  apt-get install iproute2 -y  gt   dev null  amp  amp  ip -4 route show default   cut -d    -f3 quot

User · Answer

The only way is passing the host information as environment when you create a container  run --env  lt key gt   lt value gt

User · Answer

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

User · Answer

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  lt external server port gt  80 -v  var run docker sock  tmp docker sock ro jwilder nginx-proxy   2  Start ipify container    docker run -e VIRTUAL HOST  lt external server name address gt  --detach --name ipify osixia ipify-api 0 1 0   Now when a container sends a http request to the server  e g     curl http    lt external server name address gt   lt external server port gt    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

User · Answer

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

User · Answer

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

User · Answer

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      quot ip route get 1   sed -n  s    src    0-9           1 p  quot   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

User · Answer

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] How to get the IP address of the docker host from inside a docker container

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