From inside of a Docker container how do I connect to the localhost of the machine

Question

So I have a Nginx running inside a docker container  I have a mysql running on localhost  I want to connect to the MySql from within my Nginx  The MySql is running on localhost and not exposing a port to the outside world  so its bound on localhost  not bound on the ip address of the machine   Is there any way to connect to this MySql or any other program on localhost from within this docker container   This question is different from  How to get the IP address of the docker host from inside a docker container  due to the fact that the IP address of the docker host could be the public IP or the private IP in the network which may or may not be reachable from within the docker container  I mean public IP if hosted at AWS or something   Even if you have the IP address of the docker host it does not mean you can connect to docker host from within the container given that IP address as your Docker network may be overlay  host  bridge  macvlan  none etc which restricts the reachability of that IP address

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Until host docker internal is working for every platform  you can use my container acting as a NAT gateway without any manual setup   https   github com qoomon docker-host

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Very simple and quick  check your host IP with ifconfig  linux  or ipconfig  windows  and then create a  docker-compose yml  version   3    specify docker-compose version  services    nginx      build       specify the directory of the Dockerfile     ports        -  8080 80    specify port mapping     extra hosts        -  dockerhost  lt yourIP gt     This way  your container will be able to access your host  When accessing your DB  remember to use the name you specified before  in this case  dockerhost  and the port of your host in which the DB is running

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Several solutions come to mind   Move your dependencies into containers first Make your other services externally accessible and connect to them with that external IP Run your containers without network isolation Avoid connecting over the network  use a socket that is mounted as a volume instead  The reason this doesn t work out of the box is that containers run with their own network namespace by default  That means localhost  or 127 0 0 1 pointing to the loopback interface  is unique per container  Connecting to this will connect to the container itself  and not services running outside of docker or inside of a different docker container  Option 1  If your dependency can be moved into a container  I would do this first  It makes your application stack portable as others try to run your container on their own environment  And you can still publish the port on your host where other services that have not been migrated can still reach it  You can even publish the port to the localhost interface on your docker host to avoid it being externally accessible with a syntax like  -p 127 0 0 1 3306 3306 for the published port  Option 2  There are a variety of ways to detect the host IP address from inside of the container  but each have a limited number of scenarios where they work  e g  requiring Docker for Mac   The most portable option is to inject your host IP into the container with something like an environment variable or configuration file  e g   docker run --rm -e  quot HOST IP   ip route get 1   sed -n  s    src    0-9           1 p   quot       This does require that your service is listening on that external interface  which could be a security concern  For other methods to get the host IP address from inside of the container  see this post  Slightly less portable is to use host docker internal  This works in current versions of Docker for Windows and Docker for Mac  And in 20 10  the capability has been added to Docker for Linux when you pass a special host entry with  docker run --add-host host docker internal host-gateway      The host-gateway is a special value added in Docker 20 10 that automatically expands to a host IP  For more details see this PR  Option 3  Running without network isolation  i e  running with --net host  means your application is running on the host network namespace  This is less isolation for the container  and it means you cannot access other containers over a shared docker network with DNS  instead  you need to use published ports to access other containerized applications   But for applications that need to access other services on the host that are only listening on 127 0 0 1 on the host  this can be the easiest option  Option 4  Various services also allow access over a filesystem based socket  This socket can be mounted into the container as a bind mounted volume  allowing you to access the host service without going over the network  For access to the docker engine  you often see examples of mounting  var run docker sock into the container  giving that container root access to the host   With mysql  you can try something like -v  var run mysqld mysqld sock  var run mysqld mysql sock and then connect to localhost which mysql converts to using the socket

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To make everything work  you need to create a config for your server  caddy  nginx  where the main domain will be  quot docker for mac localhost quot   For this replace in baseURL  quot http   localhost api quot  on  quot http   docker for mac localhost api quot  docker-compose yml backend    restart  always   image  backend   build      dockerfile  backend Dockerfile     context      environment        add django setting py os getenv  quot var quot   to bd config and ALLOWED HOSTS CORS ORIGIN WHITELIST     DJANGO ALLOWED PROTOCOL  http     DJANGO ALLOWED HOSTS  docker for mac localhost     POSTGRES PASSWORD  123456     POSTGRES USER  user     POSTGRES DB  bd name     WAITDB   quot 1 quot    volumes      - backend static  app static     - backend media  app media   depends on      - db  frontend    restart  always   build      dockerfile  frontend Dockerfile     context      image  frontend   environment         replace baseURL for axios     API URL  http   docker for mac localhost b api     API URL BROWSER  http   docker for mac localhost b api     NUXT HOST  0 0 0 0   depends on      - backend  caddy    image  abiosoft caddy   restart  always   volumes      -  HOME  caddy  root  caddy     -   Caddyfile local  etc Caddyfile     - backend static  static     - backend media  media   ports    - 80 80   depends on      - frontend     - backend     - db  Caddyfile local http   docker for mac localhost      proxy  b backend 5000       header upstream Host  host      header upstream X-Real-IP  remote      header upstream X-Forwarded-For  remote      header upstream X-Forwarded-Port  server port      header upstream X-Forwarded-Proto  scheme         proxy   frontend 3000       header upstream Host  host      header upstream X-Real-IP  remote      header upstream X-Forwarded-For  remote      header upstream X-Forwarded-Port  server port      header upstream X-Forwarded-Proto  scheme         root      log stdout   errors stdout   gzip    http   docker for mac localhost static     root  static    http   docker for mac localhost media     root  media    django settings py ALLOWED HOSTS    os getenv  quot DJANGO ALLOWED HOSTS quot         CORS ORIGIN WHITELIST    f  os getenv  quot DJANGO ALLOWED PROTOCOL quot       os getenv  quot DJANGO ALLOWED HOSTS quot       DATABASES          quot default quot              quot ENGINE quot    quot django db backends postgresql psycopg2 quot            quot NAME quot   os getenv  quot POSTGRES DB quot             quot USER quot   os getenv  quot POSTGRES USER quot             quot PASSWORD quot   os getenv  quot POSTGRES PASSWORD quot             quot HOST quot    quot db quot            quot PORT quot    quot 5432 quot            nuxt config js  the baseURL variable will override API URL of environment  axios      baseURL   http   127 0 0 1 8000 b api

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This worked for me on an NGINX PHP-FPM stack without touching any code or networking where the app s just expecting to be able to connect to localhost  Mount mysqld sock from the host to inside the container   Find the location of the mysql sock file on the host running mysql  netstat -ln   awk   mysql       sock    print  9     Mount that file to where it s expected in the docker  docker run -v  hostpath to mysqld sock  containerpath to mysqld sock  Possible locations of mysqld sock      tmp mysqld sock  var run mysqld mysqld sock   var lib mysql mysql sock  Applications MAMP tmp mysql mysql sock   if running via MAMP

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if you use docker-compose  maybe it can work  iptables -I INPUT   -i eth0 -p tcp --dport 8001 -j ACCEPT  the eth0 is your network interface that connect internet  and 8081 the host server port the best way for iptables rule is  iptables TRACE

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Simplest solution for Mac OSX  Just use the IP address of your Mac  On the Mac run this to get the IP address and use it from within the container     ifconfig   grep  inet 192   awk    print  2     As long as the server running locally on your Mac or in another docker container is listening to 0 0 0 0  the docker container will be able to reach out at that address   If you just want to access another docker container that is listening on 0 0 0 0 you can use 172 17 0 1

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I disagree with the answer from Thomasleveil   Making mysql bind to 172 17 42 1 will prevent other programs using the database on the host to reach it  This will only work if all your database users are dockerized   Making mysql bind to 0 0 0 0 will open the db to outside world  which is not only a very bad thing to do  but also contrary to what the original question author wants to do  He explicitly says  The MySql is running on localhost and not exposing a port to the outside world  so its bound on localhost   To answer the comment from ivant      Why not bind mysql to docker0 as well     This is not possible  The mysql mariadb documentation explicitly says it is not possible to bind to several interfaces  You can only bind to 0  1  or all interfaces   As a conclusion  I have NOT found any way to reach the  localhost only  database on the host from a docker container  That definitely seems like a very very common pattern  but I don t know how to do it

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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

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using host docker internal  instead of localhost  works flawlessly for me

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I solved it by creating a user in MySQL for the container s ip     sudo mysql lt br gt  mysql gt  create user  username   172 17 0 2  identified by  password   lt br gt  Query OK  0 rows affected  0 00 sec   mysql gt  grant all privileges on database name   to  username   172 17 0 2  with grant option  lt br gt  Query OK  0 rows affected  0 00 sec     sudo vim  etc mysql mysql conf d mysqld cnf  lt br gt bind-address          172 17 0 1    sudo systemctl restart mysql service   Then on container  jdbc mysql    lt b gt 172 17 0 1 lt  b gt  3306 database name

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Solution for Linux  kernel   3 6      Ok  your localhost server has default docker interface docker0 with ip address 172 17 0 1  Your container started with default network settings --net  bridge       Enable route localnet for docker0 interface    sysctl -w net ipv4 conf docker0 route localnet 1 Add this rules to iptables    iptables -t nat -I PREROUTING -i docker0 -d 172 17 0 1 -p tcp --dport 3306 -j DNAT --to 127 0 0 1 3306   iptables -t filter -I INPUT -i docker0 -d 127 0 0 1 -p tcp --dport 3306 -j ACCEPT Create mysql user with access from     that mean - from anyone  excluding localhost  CREATE USER  user      IDENTIFIED BY  password   Change in your script the mysql-server address to 172 17 0 1    From the kernel documentation      route localnet - BOOLEAN  Do not consider loopback addresses as martian source or destination while routing  This enables the use of 127 8 for local routing purposes  default FALSE

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None of the answers worked for me when using Docker Toolbox on Windows 10 Home  but 10 0 2 2 did  since it uses VirtualBox which exposes the host to the VM on this address

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You can get the host ip using alpine image  docker run --rm alpine ip route   awk  NR  1  print  3     This would be more consistent as you re always using alpine to run the command   Similar to Mariano s answer you can use same command to set an environment variable  DOCKER HOST   docker run --rm alpine ip route   awk  NR  1  print  3    docker-compose up

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Until fix is not merged into master branch  to get host IP just run from inside of the container   ip -4 route list match 0 0   cut -d    -f3    as suggested by  Mahoney here

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This is not an answer to the actual question  This is how I solved a similar problem  The solution comes totally from  Define Docker Container Networking so Containers can Communicate  Thanks to Nic Raboy  Leaving this here for others who might want to do REST calls between one container and another  Answers the question  what to use in place of localhost in a docker environment   Get how your network looks like docker network ls  Create a new network docker network create -d my-net  Start the first container docker run -d -p 5000 5000 --network  my-net  --name  first container   lt MyImage1 v0 1 gt   Check out network settings for first container docker inspect first container   Networks   should have  my-net   Start the second container docker run -d -p 6000 6000 --network  my-net  --name  second container   lt MyImage2 v0 1 gt   Check out network settings for second container docker inspect second container   Networks   should have  my-net   ssh into your second container docker exec -it second container sh or docker exec -it second container bash   Inside of the second container  you can ping the first container by ping first container  Also  your code calls such as http   localhost 5000 can be replaced by http   first container 5000

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For Linux  where you cannot change the interface the localhost service binds to  There are two problems we need to solve   Getting the IP of the host Making our localhost service available to Docker   The first problem can be solved using qoomon s docker-host image  as given by other answers   You will need to add this container to the same bridge network as your other container so that you can access it  Open a terminal inside your container and ensure that you can ping dockerhost   bash-5 0  ping dockerhost PING dockerhost  172 20 0 2   56 data bytes 64 bytes from 172 20 0 2  seq 0 ttl 64 time 0 523 ms   Now  the harder problem  making the service accessible to docker   We can use telnet to check if we can access a port on the host  you may need to install this    The problem is that our container will only be able to access services that bind to all interfaces  such as SSH   bash-5 0  telnet dockerhost 22 SSH-2 0-OpenSSH 7 6p1 Ubuntu-4ubuntu0 3   But services bound only to localhost will be inaccessible   bash-5 0  telnet dockerhost 1025 telnet  can t connect to remote host  172 20 0 2   Connection refused   The proper solution here would be to bind the service to dockers bridge network  However  this answer assumes that it is not possible for you to change this  So we will instead use iptables   First  we need to find the name of the bridge network that docker is using with ifconfig  If you are using an unnamed bridge  this will just be docker0  However  if you are using a named network you will have a bridge starting with br- that docker will be using instead  Mine is br-5cd80298d6f4   Once we have the name of this bridge  we need to allow routing from this bridge to localhost  This is disabled by default for security reasons   sysctl -w net ipv4 conf  lt bridge name gt  route localnet 1   Now to set up our iptables rule  Since our container can only access ports on the docker bridge network  we are going to pretend that our service is actually bound to a port on this network   To do this  we will forward all requests to  lt docker bridge gt  port to localhost port  iptables -t nat -A PREROUTING -p tcp -i  lt docker bridge name gt  --dport  lt service port gt  -j DNAT --to-destination 127 0 0 1  lt service port gt    For example  for my service on port 1025  iptables -t nat -A PREROUTING -p tcp -i br-5cd80298d6f4 --dport 1025 -j DNAT --to-destination 127 0 0 1 1025   You should now be able to access your service from the container   bash-5 0  telnet dockerhost 1025 220 127 0 0 1 ESMTP Service Ready

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The way I do it is pass the host IP as environment variable to container  Container then access the host by that variable

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Solution for Windows 10  Docker Community Edition 17 06 0-ce-win18 2017-06-28  stable   You can use DNS name of the host docker for win localhost  to resolve to the internal IP   Warning some sources mentioned windows but it should be win   Overview I needed to do something similar  that is connect from my Docker container to my localhost  which was running the Azure Storage Emulator and CosmosDB Emulator   The Azure Storage Emulator by default listens on 127 0 0 1  while you can change the IP its bound too  I was looking for a solution that would work with default settings   This also works for connecting from my Docker container to SQL Server and IIS  both running locally on my host with default port settings

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First see this answer for the options that you have to fix this problem  But if you use docker-compose you can add network mode  host to your service and then use 127 0 0 1 to connect to the local host  This is just one of the options described in the answer above  Below you can find how I modified docker-compose yml from https   github com geerlingguy php-apache-container git   ---  version   quot 3 quot   services     php-apache       network mode  host      image  geerlingguy php-apache latest      container name  php-apache        indicates the line I added    Additional info  This has also worked in version 2 2  and  quot host quot  or just  host  are both worked in docker-compose   ---  version   quot 2 2 quot    services     php-apache       network mode   quot host quot          or      network mode  host

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For those on Windows  assuming you re using the bridge network driver  you ll want to specifically bind MySQL to the ip address of the hyper-v network interface    This is done via the configuration file under the normally hidden C  ProgramData MySQL folder    Binding to 0 0 0 0 will not work  The address needed is shown in the docker configuration as well  and in my case was 10 0 75 1

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For windows    I have changed the database url in spring configuration  spring datasource url jdbc postgresql   host docker internal 5432 apidb  Then build the image and run  It worked for me

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The CGroups and Namespaces are playing major role in the Container Ecosystem   Namespace provide a layer of isolation  Each container runs in a separate namespace and its access is limited to that namespace  The Cgroups controls the resource utilization of each container  whereas Namespace controls what a process can see and access the respective resource    Here is the basic understanding of the solution approach you could follow   Use Network Namespace  When a container spawns out of image  a network interface is defined and create  This gives the container unique IP address and interface     docker run -it alpine ifconfig   By changing the namespace to host  cotainers networks does not remain isolated to its interface  the process will have access to host machines network interface     docker run -it --net host alpine ifconfig   If the process listens on ports  they ll be listened on the host interface and mapped to the container   Use PID Namespace By changing the Pid namespace allows a container to interact with other process beyond its normal scope   This container will run in its own namespace     docker run -it alpine ps aux   By changing the namespace to the host  the container can also see all the other processes running on the system     docker run -it --pid host alpine ps aux   Sharing Namespace  This is a bad practice to do this in production because you are breaking out of the container security model which might open up for vulnerabilities  and easy access to eavesdropper  This is only for debugging tools and understating the loopholes in container security   The first container is nginx server  This will create a new network and process namespace  This container will bind itself to port 80 of newly created network interface      docker run -d --name http nginx alpine   Another container can now reuse this namespace     docker run --net container http mohan08p curl curl -s localhost   Also  this container can see the interface with the processes in a shared container     docker run --pid container http alpine ps aux   This will allow you give more privileges to containers without changing or restarting the application  In the similar way you can connect to mysql on host  run and debug your application  But  its not recommend to go by this way  Hope it helps

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You can simply do ifconfig on host machine to check your host IP  then connect to the ip from within your container  works perfectly for me

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Edit  I ended up prototyping out the concept on GitHub  Check out  https   github com sivabudh system-in-a-box    First  my answer is geared towards 2 groups of people  those who use a Mac  and those who use Linux   The host network mode doesn t work on a Mac  You have to use an IP alias  see  https   stackoverflow com a 43541681 2713729  What is a host network mode  See  https   docs docker com engine reference run   network-settings  Secondly  for those of you who are using Linux  my direct experience was with Ubuntu 14 04 LTS and I m upgrading to 16 04 LTS in production soon   yes  you can make the service running inside a Docker container connect to localhost services running on the Docker host  eg  your laptop    How   The key is when you run the Docker container  you have to run it with the host mode  The command looks like this   docker run --network  host  -id  lt Docker image ID gt   When you do an ifconfig  you will need to apt-get install net-tools your container for ifconfig to be callable  inside your container  you will see that the network interfaces are the same as the one on Docker host  eg  your laptop     It s important to note that I m a Mac user  but I run Ubuntu under Parallels  so using a Mac is not a disadvantage   -   And this is how you connect NGINX container to the MySQL running on a localhost

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You need to know the gateway  My solution with local server was to expose it under 0 0 0 0 8000  then run docker with subnet and run container like   docker network create --subnet 172 35 0 0 16 --gateway 172 35 0 1 SUBNET35 docker run -d -p 4444 4444 --net SUBNET35  lt container-you-want-run-place-here gt    So  now you can access your loopback through http   172 35 0 1 8000

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I doing a hack similar to above posts of get the local IP to map to a alias name  DNS  in the container  The major problem is to get dynamically with a simple script that works both in Linux and OSX the host IP address  I did this script that works in both environments  even in Linux distribution with   LANG      en    configured    ifconfig   grep -E    0-9  1 3     3  0-9  1 3     grep -v 127 0 0 1   awk    print  2      cut -f2 -d    head -n1   So  using Docker Compose  the full configuration will be   Startup script  docker-run sh    export DOCKERHOST   ifconfig   grep -E    0-9  1 3     3  0-9  1 3     grep -v 127 0 0 1   awk    print  2      cut -f2 -d    head -n1  docker-compose -f docker-compose yml up   docker-compose yml   myapp    build      ports      -  80 80    extra hosts      -  dockerhost  DOCKERHOST    Then change http   localhost to http   dockerhost in your code   For a more advance guide of how to customize the DOCKERHOST script  take a look at this post with a explanation of how it works

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Here is my solution   it works for my case   set local mysql server to public access by comment      bind-address     127 0 0 1   in  etc mysql mysql conf d restart mysql server  sudo  etc init d mysql restart run the following command to open user root access any host mysql -uroot -proot GRANT ALL PRIVILEGES ON     TO  root      IDENTIFIED BY  root  WITH  GRANT OPTION  FLUSH PRIVILEGES   create sh script   run docker sh          bin bash      HOSTIP  ip -4 addr show scope global dev eth0   grep inet   awk   print   2     cut -d   -f 1          docker run -it -d --name web-app                     --add-host local   HOSTIP                      -p 8080 8080                     -e DATABASE HOST   HOSTIP                      -e DATABASE PORT 3306                     -e DATABASE NAME demo                     -e DATABASE USER root                     -e DATABASE PASSWORD root                     sopheamak springboot docker mysql       run with docker-composer   version   2 1   services    tomcatwar       extra hosts          -  local 10 1 2 232       image  sopheamak springboot docker mysql      ports           - 8080 8080      environment              - DATABASE HOST local             - DATABASE USER root             - DATABASE PASSWORD root             - DATABASE NAME demo             - DATABASE PORT 3306

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Try this   version   3 5  services    yourservice-here      container name  container name     ports        -  4000 4000      extra hosts     lt ---- here       - localhost 192 168 1 202       - or-vitualhost local 192 168 1 202   To get 192 168 1 202  uses ifconfig  This worked for me  Hope this help

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For Windows Machine  -  Run the below command to Expose docker port randomly during build time   docker run -d --name MyWebServer -P mediawiki       In the above container list you can see the port assigned as 32768  Try accessing   localhost 32768    You can see the mediawiki page

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Connect to the gateway address    docker network inspect bridge   grep Gateway                      quot Gateway quot    quot 172 17 0 1 quot   Make sure the process on the host is listening on this interface  i e 172 17 0 1 in my machine   It works for me in linux    python -m http server  amp  gt   dev null  amp   1  149976    docker run --rm python python -c   quot from urllib request import urlopen print b Directory listing for  in urlopen  http   172 17 0 1 8000   read    quot   True

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Edit  If you are using Docker-for-mac or Docker-for-Windows 18 03   just connect to your mysql service using the host host docker internal  instead of the 127 0 0 1 in your connection string   As of Docker 18 09 3  this does not work on Docker-for-Linux  A fix has been submitted on March the 8th  2019 and will hopefully be merged to the code base  Until then  a workaround is to use a container as described in qoomon s answer  2020-01  some progress has been made  If all goes well  this should land in Docker 20 04 Docker 20 10-beta1 has been reported to implement host docker internal     docker run --rm --add-host host docker internal host-gateway alpine ping host docker internal PING host docker internal  172 17 0 1   56 data bytes 64 bytes from 172 17 0 1  seq 0 ttl 64 time 0 534 ms 64 bytes from 172 17 0 1  seq 1 ttl 64 time 0 176 ms       TLDR Use --network  quot host quot  in your docker run command  then 127 0 0 1 in your docker container will point to your docker host  Note  This mode only works on Docker for Linux  per the documentation   Note on docker container networking modes Docker offers different networking modes when running containers  Depending on the mode you choose you would connect to your MySQL database running on the docker host differently  docker run --network  quot bridge quot   default  Docker creates a bridge named docker0 by default  Both the docker host and the docker containers have an IP address on that bridge  on the Docker host  type sudo ip addr show docker0 you will have an output looking like   vagrant docker      sudo ip addr show docker0 4  docker0   lt BROADCAST MULTICAST UP LOWER UP gt  mtu 1500 qdisc noqueue state UP group default     link ether 56 84 7a fe 97 99 brd ff ff ff ff ff ff     inet 172 17 42 1 16 scope global docker0        valid lft forever preferred lft forever     inet6 fe80  5484 7aff fefe 9799 64 scope link        valid lft forever preferred lft forever  So here my docker host has the IP address 172 17 42 1 on the docker0 network interface  Now start a new container and get a shell on it  docker run --rm -it ubuntu trusty bash and within the container type ip addr show eth0 to discover how its main network interface is set up  root e77f6a1b3740    ip addr show eth0 863  eth0   lt BROADCAST UP LOWER UP gt  mtu 1500 qdisc pfifo fast state UP group default qlen 1000     link ether 66 32 13 f0 f1 e3 brd ff ff ff ff ff ff     inet 172 17 1 192 16 scope global eth0        valid lft forever preferred lft forever     inet6 fe80  6432 13ff fef0 f1e3 64 scope link        valid lft forever preferred lft forever  Here my container has the IP address 172 17 1 192  Now look at the routing table  root e77f6a1b3740    route Kernel IP routing table Destination     Gateway         Genmask         Flags Metric Ref    Use Iface default         172 17 42 1     0 0 0 0         UG    0      0        0 eth0 172 17 0 0                      255 255 0 0     U     0      0        0 eth0  So the IP Address of the docker host 172 17 42 1 is set as the default route and is accessible from your container  root e77f6a1b3740    ping 172 17 42 1 PING 172 17 42 1  172 17 42 1  56 84  bytes of data  64 bytes from 172 17 42 1  icmp seq 1 ttl 64 time 0 070 ms 64 bytes from 172 17 42 1  icmp seq 2 ttl 64 time 0 201 ms 64 bytes from 172 17 42 1  icmp seq 3 ttl 64 time 0 116 ms  docker run --network  quot host quot  Alternatively you can run a docker container with network settings set to host  Such a container will share the network stack with the docker host and from the container point of view  localhost  or 127 0 0 1  will refer to the docker host  Be aware that any port opened in your docker container would be opened on the docker host  And this without requiring the -p or -P docker run option  IP config on my docker host   vagrant docker      ip addr show eth0 2  eth0   lt BROADCAST MULTICAST UP LOWER UP gt  mtu 1500 qdisc pfifo fast state UP group default qlen 1000     link ether 08 00 27 98 dc aa brd ff ff ff ff ff ff     inet 10 0 2 15 24 brd 10 0 2 255 scope global eth0        valid lft forever preferred lft forever     inet6 fe80  a00 27ff fe98 dcaa 64 scope link        valid lft forever preferred lft forever  and from a docker container in host mode   vagrant docker      docker run --rm -it --network host ubuntu trusty ip addr show eth0 2  eth0   lt BROADCAST MULTICAST UP LOWER UP gt  mtu 1500 qdisc pfifo fast state UP group default qlen 1000     link ether 08 00 27 98 dc aa brd ff ff ff ff ff ff     inet 10 0 2 15 24 brd 10 0 2 255 scope global eth0        valid lft forever preferred lft forever     inet6 fe80  a00 27ff fe98 dcaa 64 scope link        valid lft forever preferred lft forever  As you can see both the docker host and docker container share the exact same network interface and as such have the same IP address   Connecting to MySQL from containers bridge mode To access MySQL running on the docker host from containers in bridge mode  you need to make sure the MySQL service is listening for connections on the 172 17 42 1 IP address  To do so  make sure you have either bind-address   172 17 42 1 or bind-address   0 0 0 0 in your MySQL config file  my cnf   If you need to set an environment variable with the IP address of the gateway  you can run the following code in a container   export DOCKER HOST IP   route -n   awk   UG   t   print  2     then in your application  use the DOCKER HOST IP environment variable to open the connection to MySQL  Note  if you use bind-address   0 0 0 0 your MySQL server will listen for connections on all network interfaces  That means your MySQL server could be reached from the Internet   make sure to setup firewall rules accordingly  Note 2  if you use bind-address   172 17 42 1 your MySQL server won t listen for connections made to 127 0 0 1  Processes running on the docker host that would want to connect to MySQL would have to use the 172 17 42 1 IP address  host mode To access MySQL running on the docker host from containers in host mode  you can keep bind-address   127 0 0 1 in your MySQL configuration and all you need to do is to connect to 127 0 0 1 from your containers   vagrant docker      docker run --rm -it --network host mysql mysql -h 127 0 0 1 -uroot -p Enter password  Welcome to the MySQL monitor   Commands end with   or  g  Your MySQL connection id is 36 Server version  5 5 41-0ubuntu0 14 04 1  Ubuntu   Copyright  c  2000  2014  Oracle and or its affiliates  All rights reserved   Oracle is a registered trademark of Oracle Corporation and or its affiliates  Other names may be trademarks of their respective owners   Type  help   or   h  for help  Type   c  to clear the current input statement   mysql gt   note  Do use mysql -h 127 0 0 1 and not mysql -h localhost  otherwise the MySQL client would try to connect using a unix socket

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