This question already has answers here:
From inside of a Docker container, how do I connect to the localhost of the machine?
(40 answers)
Closed 11 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.
I'm setting up the service at Oracle Free Tier service; the service is up and running on local interfaces, but I can't reach it from outside (via public IP) on port 8065.
No firewall rules on Ubuntu machine, Oracle firewall is configured and says "TCP traffic for ports: 8065". Exact same (build-in) rule works just fine.
Oracle's Ubuntu default image, Linux's firewall seems to be disabled:
$ sudo ufw status
Status: inactive
I'm getting "Connection refused" (TCP level) from outside, when trying to connect.
Any help would be much appreciated.
it's turned out that a posted answer works - as an Oracle's Ubuntu instance use iptables, so, you need not only to work on the cloud's firewall and ufw, but on iptables level as well, quoting related answer:
Opening port 80 on Oracle Cloud Infrastructure Compute node
Oracle Ubuntu have in build iptables rules in Ubuntu20， you have two choice
enable ufw
sudo ufw allow HTTP
sudo ufw enable
sudo systemctl enable ufw
disable ufw and config iptables
Sometimes ufw is not Compatible with iptables in Ubuntu20
such as， if you use mosh need open udp port 60000-61000
detele /etc/iptables/rules.v4 and v6
Closed. This question does not meet Stack Overflow guidelines. It is not currently accepting answers.
This question does not appear to be about a specific programming problem, a software algorithm, or software tools primarily used by programmers. If you believe the question would be on-topic on another Stack Exchange site, you can leave a comment to explain where the question may be able to be answered.
Closed 2 years ago.
The community reviewed whether to reopen this question 11 months ago and left it closed:
Original close reason(s) were not resolved
Improve this question
This is an elementary question however one I cannot seem to resolve by perusing the Oracle Cloud Infrastructure documentation. I've created an Ubuntu-based compute node, and it's attached to a subnet. In that subnet I've created a stateful rule with source 0.0.0.0/0, IP protocol: TCP, Source Port Range: All, Destination Port Range: 80.
There is no firewall configured on the server.
Despite this configuration I can't access the compute node's public IP. Any ideas?
I figured it out. The connectivity issue was due to Oracle's default use of iptables on all Oracle-provided images. Literally the very first thing I did when spinning up this instance was check ufw, presuming there were a few firewall restrictions in place. The ufw status was inactive, so I concluded the firewall was locally wide open. Because to my understanding both ufw and iptables look at the netfilter kernel firewall, and because ufw is the de facto (standard?) firewall solution on Ubuntu, I've no idea why they concluded it made sense to use iptables in this fashion. Maybe just to standardize across all images?
I learned about the rules by running:
$ sudo iptables -L
Then I saved the rules to a file so I could add the relevant ones back later:
$ sudo iptables-save > ~/iptables-rules
Then I ran these rules to effectively disable iptables by allowing all traffic through:
$ iptables -P INPUT ACCEPT
$ iptables -P OUTPUT ACCEPT
$ iptables -P FORWARD ACCEPT
$ iptables -F
To clear all iptables rules at once, run this command:
$ iptables --flush
Anyway, hope this helps somebody else out because documentation on the matter is non-existent.
When deploying compute instances at Oracle Cloud Infrastructure you need to take into account few things:
Create Internet Gateway (IGW).
Define routes to point to IGW.
Allow port 80 in the Security List associated with the IGW. By default you only have access to SSH and ICMP 3,4 type.
Allow connectivity on Compute's instance firewall (which is enabled by default).
In your example if you are using a OEL shape:
$ sudo firewall-cmd --zone=public --permanent --add-port=80/tcp
$ sudo firewall-cmd --reload
Always refer to the official guide: https://docs.cloud.oracle.com/en-us/iaas/developer-tutorials/tutorials/apache-on-ubuntu/01oci-ubuntu-apache-summary.htm
$ sudo iptables -I INPUT 6 -m state --state NEW -p tcp --dport 80 -j ACCEPT
$ sudo netfilter-persistent save
$ sudo systemctl restart apache2
credited to https://medium.com/#fathi.ria/oracle-database-cloud-open-ports-on-oci-1af24f4eb9f2
Coumputer Instance(Such as Ubuntu) -> Virtual Cloud Network -> Security List -> Ingress Rules -> Please add a rule to allow access to port 80 from anywhere
Pre-Requisite
VM instance should have been created and running
Access to Public and Private keys used during the creation of VM instance
Log into the VM using SSH and run the following command
$ sudo iptables --list --line-numbers
It will show the details about Chain INPUT (policy ACCEPT). From the list
required to Delete REJECT all rule in the IPTABLES.
$ sudo iptables -D INPUT <Reject Line number>
e.g.
$ sudo iptables -D INPUT 6
Check if the REJECT rule is deleted
sudo iptables --list --line-numbers
Access the Default Security List and Edit Ingress Rules to Allow Internet Traffic on Port
Edit the INGRES Rule Add CIDR 0.0.0.0/0 TCP Destination 9999
(N): Networking >Virtual Cloud Networks> Virtual Cloud Network Details>Security Lists> Security List Details
Access your application via web browser
Type http://<public IP address of the VM>:port
I guess if you add the rule below to your iptables it should work; otherwise you'll be disturbing other rules which are related to block volume attachment that comes preconfigured on those Oracle images.
iptables -I INPUT 5 -i ens3 -p tcp --dport 80 -m state --state NEW,ESTABLISHED -j ACCEPT
If you have not created Internet Gateway yet, that might be the reason. In order to connect the VCN with the public internet you need to have an Internet Gateway and a route table to direct the traffic through the gateway.
I have a Fedora 21 server running on a local private LAN. I have setup a minecraft server. It is running on port 25565 and running the server produces no errors. My problem is that I cannot get the client to connect to it. The client connects fine to minecraft servers outside of the local private LAN and when I tested minecraft server on an Ubuntu desktop, the windows machine was able to connect to that server. So, it seems isolated to the Fedora 21 machine. It is running as a server, so no GUI! I have performed a netstat -a on it and see that it states that it is listening to port 25565. I have turned off firewalld ('sudo systemctl stop firewalld' and then 'sudo systemctl disable firewalld' just to be sure) to see if that was blocking it. I was still not able to connect. I can provide other information as needed. Oh, I am also using Java 1.8u25 and minecraft_server.1.8.1.
Thanks for your help.
I have found the problem. Apparently the change requires a server reboot. Perhaps just restarting the service may also take care of the issue but definitely rebooting the server cleared the problem.
EDIT: I have found that using iptables will open the firewall to allow the game to connect. I only stated that turning off firewalld allows the game to operate after saving iptables and restarting firewalld.
This should work (let me know if it doesn't):
Be sure to place this before any REJECT statements in the iptables.
You can use iptables -L --line-numbers | less to display the table. I pipe it out to "less" because the table can be quite long and this way one can easily scroll through the information.
iptables -I INPUT ## -p tcp --dport 25565 -j ACCEPT
iptables -I INPUT ## -p udp --dport 25565 -j ACCEPT
iptables-save
To do a restart of the firewalld type sudo systemctl restart firewalld.
Also keep in mind that this is for the default port in server.properties file. Obviously if the default port is changed in this file, then so would the iptables setting.
Hopefully this will help anyone who may run into this same problem.