Everytime I try to start any container in bridged network mode, the virtual network adapter is not added to the docker0 bridge. As a result, these containers don't have access to the network. I see the docker0 bridge and vethXXXXXX#ifXXX virtual interface from ip addr. However, brctl show shows the docker0 bridge with no interface attached. I can manually add the interface using brctl addif vethXXXXXX docker0 and everything works fine.
Some containers exit so quickly due to the connection problem that I don't have a chance to add them before they get a new virtual interface when restarting.
I already deleted all the docker network adapter and let them reinitialize by restarting docker, without success.
Does anybody know how I can fix this, so that network interfaces of container get automatically added to the docker0 bridge on startup?
Thanks
You can use networkctl to check veth status.
networkctl status -a
It might match incorrect network setting. You can use another higher priority systemd-networkd setting to correct it.
ex:
Create a new file /etc/systemd/network/20-docker-veth.network
with content
[Match]
Name=veth*
Driver=veth
[Link]
Unmanaged=true
and restart the systemd-networkd service.
sudo systemctl restart systemd-networkd.service
Then, start a new container with bridge network would auto link to veth.
ref: https://forums.docker.com/t/archlinux-container-veth-interfaces-being-assigned-to-wrong-bridge/107197/2
I have a server with several virtual machines running. I am starting a container with Jira installation and i need the container to be assigned with different address from the DHCP and not use the host IP address. I am a noobie so please explain
The technique suggested in #ad22's answer requires a custom build of the Docker engine that uses a fork of libnetwork. Now, more than four years after that hack was developed, the DHCP feature has still not been merged into the standard Docker engine, and the fork has fallen far behind the mainline code.
Since late 2019, it has been possible to assign IP addresses to Docker containers with DHCP using devplayer0's docker-net-dhcp plugin, which works with the standard Docker engine. When you create a new container, this plugin starts a Busybox udhcpc client to obtain a DHCP lease, then runs udhcpc (in a process outside the container's PID namespace) to renew the lease as needed.
As found in the other answer, using the macvlan will not enable the container to obtain addresses from DHCP. The functionality to obtain addresses from DHCP is experimental (this was created by someone associated with the docker libnetwork project)
https://gist.github.com/nerdalert/3d2b891d41e0fa8d688c
It suggests compiling the changes into the docker binary and then running
docker network create -d macvlan \
--ipam-driver=dhcp \
-o parent=eth0 \
--ipam-opt dhcp_interface=eth0 mcv0
Since this requires re-compiling the binary, an alternate solution could be to
assign static IP addresses to all your containers using the "--ip" option to docker run/compose, and get a DNS entry for your hostname assigned to this IP, and also ensure that the IP can never be assigned through DHCP.
You can achieve this using the docker network macvlan driver. According to the docs:
...you can use the macvlan network driver to assign a MAC address to each container’s virtual network interface, making it appear to be a physical network interface directly connected to the physical network.
So essentially, the virtual network interface will use the physical network interface exposed on the host to advertise its own virtual MAC address. This will then be broadcast to the LAN on which the DHCP server is operating, and the virtual interface will be assigned an IP.
The steps to get it going are:
Create a docker network which uses the macvlan driver:
docker network create \
--driver macvlan \
--subnet=172.16.86.0/24 \
--gateway=172.16.86.1 \
--opt parent=eth0 lan_net
The subnet and gateway would be those of your LAN network (on which the DHCP resides). The parent option specifies the physical interface on the host through which you would like your virtual interface to be exposed to the LAN network.
Run your container using the newly created network:
docker run -it --rm --net=lan_net alpine
This question already has answers here:
From inside of a Docker container, how do I connect to the localhost of the machine?
(41 answers)
Closed 12 months ago.
I have a docker container running jenkins. As part of the build process, I need to access a web server that is run locally on the host machine. Is there a way the host web server (which can be configured to run on a port) can be exposed to the jenkins container?
I'm running docker natively on a Linux machine.
UPDATE:
In addition to #larsks answer below, to get the IP address of the Host IP from the host machine, I do the following:
ip addr show docker0 | grep -Po 'inet \K[\d.]+'
For all platforms
Docker v 20.10 and above (since December 14th 2020)
On Linux, add --add-host=host.docker.internal:host-gateway to your Docker command to enable this feature. (See below for Docker Compose configuration.)
Use your internal IP address or connect to the special DNS name host.docker.internal which will resolve to the internal IP address used by the host.
To enable this in Docker Compose on Linux, add the following lines to the container definition:
extra_hosts:
- "host.docker.internal:host-gateway"
For macOS and Windows
Docker v 18.03 and above (since March 21st 2018)
Use your internal IP address or connect to the special DNS name host.docker.internal which will resolve to the internal IP address used by the host.
Linux support pending https://github.com/docker/for-linux/issues/264
MacOS with earlier versions of Docker
Docker for Mac v 17.12 to v 18.02
Same as above but use docker.for.mac.host.internal instead.
Docker for Mac v 17.06 to v 17.11
Same as above but use docker.for.mac.localhost instead.
Docker for Mac 17.05 and below
To access host machine from the docker container you must attach an IP alias to your network interface. You can bind whichever IP you want, just make sure you're not using it to anything else.
sudo ifconfig lo0 alias 123.123.123.123/24
Then make sure that you server is listening to the IP mentioned above or 0.0.0.0. If it's listening on localhost 127.0.0.1 it will not accept the connection.
Then just point your docker container to this IP and you can access the host machine!
To test you can run something like curl -X GET 123.123.123.123:3000 inside the container.
The alias will reset on every reboot so create a start-up script if necessary.
Solution and more documentation here: https://docs.docker.com/docker-for-mac/networking/#use-cases-and-workarounds
When running Docker natively on Linux, you can access host services using the IP address of the docker0 interface. From inside the container, this will be your default route.
For example, on my system:
$ ip addr show docker0
7: docker0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default
link/ether 00:00:00:00:00:00 brd ff:ff:ff:ff:ff:ff
inet 172.17.0.1/16 brd 172.17.255.255 scope global docker0
valid_lft forever preferred_lft forever
inet6 fe80::f4d2:49ff:fedd:28a0/64 scope link
valid_lft forever preferred_lft forever
And inside a container:
# ip route show
default via 172.17.0.1 dev eth0
172.17.0.0/16 dev eth0 src 172.17.0.4
It's fairly easy to extract this IP address using a simple shell
script:
#!/bin/sh
hostip=$(ip route show | awk '/default/ {print $3}')
echo $hostip
You may need to modify the iptables rules on your host to permit
connections from Docker containers. Something like this will do the
trick:
# iptables -A INPUT -i docker0 -j ACCEPT
This would permit access to any ports on the host from Docker
containers. Note that:
iptables rules are ordered, and this rule may or may not do the
right thing depending on what other rules come before it.
you will only be able to access host services that are either (a)
listening on INADDR_ANY (aka 0.0.0.0) or that are explicitly
listening on the docker0 interface.
If you are using Docker on MacOS or Windows 18.03+, you can connect to the magic hostname host.docker.internal.
Lastly, under Linux you can run your container in the host network namespace by setting --net=host; in this case localhost on your host is the same as localhost inside the container, so containerized service will act like non-containerized services and will be accessible without any additional configuration.
Use --net="host" in your docker run command, then localhost in your docker container will point to your docker host.
The answer is...
Replace http://127.0.0.1 or http://localhost with http://host.docker.internal.
Why?
Source in the docs of Docker.
My google search brought me to here, and after digging in the comments I found it's a duplicate of From inside of a Docker container, how do I connect to the localhost of the machine?. I voted for closing this one as a duplicate, but since people (including myself!) often scroll down on the answers rather than reading the comments carefully, here is a short answer.
For linux systems, you can – starting from major version 20.04 of the docker engine – now also communicate with the host via host.docker.internal. This won't work automatically, but you need to provide the following run flag:
--add-host=host.docker.internal:host-gateway
See
https://github.com/moby/moby/pull/40007#issuecomment-578729356
https://github.com/docker/for-linux/issues/264#issuecomment-598864064
Solution with docker-compose:
For accessing to host-based service, you can use network_mode parameter
https://docs.docker.com/compose/compose-file/#network_mode
version: '3'
services:
jenkins:
network_mode: host
EDIT 2020-04-27: recommended for use only in local development environment.
EDIT 2021-09-21: IHaveHandedInMyResignation wrote it does not work for Mac and Windows. Option is supported only for Linux
I created a docker container for doing exactly that https://github.com/qoomon/docker-host
You can then simply use container name dns to access host system e.g.
curl http://dockerhost:9200
Currently the easiest way to do this on Mac and Windows is using host host.docker.internal, that resolves to host machine's IP address. Unfortunately it does not work on linux yet (as of April 2018).
We found that a simpler solution to all this networking junk is to just use the domain socket for the service. If you're trying to connect to the host anyway, just mount the socket as a volume, and you're on your way. For postgresql, this was as simple as:
docker run -v /var/run/postgresql:/var/run/postgresql
Then we just set up our database connection to use the socket instead of network. Literally that easy.
I've explored the various solution and I find this the least hacky solution:
Define a static IP address for the bridge gateway IP.
Add the gateway IP as an extra entry in the extra_hosts directive.
The only downside is if you have multiple networks or projects doing this, you have to ensure that their IP address range do not conflict.
Here is a Docker Compose example:
version: '2.3'
services:
redis:
image: "redis"
extra_hosts:
- "dockerhost:172.20.0.1"
networks:
default:
ipam:
driver: default
config:
- subnet: 172.20.0.0/16
gateway: 172.20.0.1
You can then access ports on the host from inside the container using the hostname "dockerhost".
For docker-compose using bridge networking to create a private network between containers, the accepted solution using docker0 doesn't work because the egress interface from the containers is not docker0, but instead, it's a randomly generated interface id, such as:
$ ifconfig
br-02d7f5ba5a51: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.32.1 netmask 255.255.240.0 broadcast 192.168.47.255
Unfortunately that random id is not predictable and will change each time compose has to recreate the network (e.g. on a host reboot). My solution to this is to create the private network in a known subnet and configure iptables to accept that range:
Compose file snippet:
version: "3.7"
services:
mongodb:
image: mongo:4.2.2
networks:
- mynet
# rest of service config and other services removed for clarity
networks:
mynet:
name: mynet
ipam:
driver: default
config:
- subnet: "192.168.32.0/20"
You can change the subnet if your environment requires it. I arbitrarily selected 192.168.32.0/20 by using docker network inspect to see what was being created by default.
Configure iptables on the host to permit the private subnet as a source:
$ iptables -I INPUT 1 -s 192.168.32.0/20 -j ACCEPT
This is the simplest possible iptables rule. You may wish to add other restrictions, for example by destination port. Don't forget to persist your iptables rules when you're happy they're working.
This approach has the advantage of being repeatable and therefore automatable. I use ansible's template module to deploy my compose file with variable substitution and then use the iptables and shell modules to configure and persist the firewall rules, respectively.
This is an old question and had many answers, but none of those fit well enough to my context. In my case, the containers are very lean and do not contain any of the networking tools necessary to extract the host's ip address from within the container.
Also, usin the --net="host" approach is a very rough approach that is not applicable when one wants to have well isolated network configuration with several containers.
So, my approach is to extract the hosts' address at the host's side, and then pass it to the container with --add-host parameter:
$ docker run --add-host=docker-host:`ip addr show docker0 | grep -Po 'inet \K[\d.]+'` image_name
or, save the host's IP address in an environment variable and use the variable later:
$ DOCKERIP=`ip addr show docker0 | grep -Po 'inet \K[\d.]+'`
$ docker run --add-host=docker-host:$DOCKERIP image_name
And then the docker-host is added to the container's hosts file, and you can use it in your database connection strings or API URLs.
For me (Windows 10, Docker Engine v19.03.8) it was a mix of https://stackoverflow.com/a/43541732/7924573 and https://stackoverflow.com/a/50866007/7924573 .
change the host/ip to host.docker.internal
e.g.: LOGGER_URL = "http://host.docker.internal:8085/log"
set the network_mode to bridge (if you want to maintain the port forwarding; if not use host):
version: '3.7'
services:
server:
build: .
ports:
- "5000:5000"
network_mode: bridge
or alternatively: Use --net="bridge" if you are not using docker-compose (similar to https://stackoverflow.com/a/48806927/7924573)
As pointed out in previous answers: This should only be used in a local development environment.
For more information read: https://docs.docker.com/compose/compose-file/#network_mode and https://docs.docker.com/docker-for-windows/networking/#use-cases-and-workarounds
You can access the local webserver which is running in your host machine in two ways.
Approach 1 with public IP
Use host machine public IP address to access webserver in Jenkins docker container.
Approach 2 with the host network
Use "--net host" to add the Jenkins docker container on the host's network stack. Containers which are deployed on host's stack have entire access to the host interface. You can access local webserver in docker container with a private IP address of the host machine.
NETWORK ID NAME DRIVER SCOPE
b3554ea51ca3 bridge bridge local
2f0d6d6fdd88 host host local
b9c2a4bc23b2 none null local
Start a container with the host network
Eg: docker run --net host -it ubuntu and run ifconfig to list all available network IP addresses which are reachable from docker container.
Eg: I started a nginx server in my local host machine and I am able to access the nginx website URLs from Ubuntu docker container.
docker run --net host -it ubuntu
$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
a604f7af5e36 ubuntu "/bin/bash" 22 seconds ago Up 20 seconds ubuntu_server
Accessing the Nginx web server (running in local host machine) from Ubuntu docker container with private network IP address.
root#linuxkit-025000000001:/# curl 192.168.x.x -I
HTTP/1.1 200 OK
Server: nginx/1.15.10
Date: Tue, 09 Apr 2019 05:12:12 GMT
Content-Type: text/html
Content-Length: 612
Last-Modified: Tue, 26 Mar 2019 14:04:38 GMT
Connection: keep-alive
ETag: "5c9a3176-264"
Accept-Ranges: bytes
In almost 7 years the question was asked, it is either docker has changed, or no one tried this way. So I will include my own answer.
I have found all answers use complex methods. Today, I have needed this, and found 2 very simple ways:
use ipconfig or ifconfig on your host and make note of all IP addresses. At least two of them can be used by the container.
I have a fixed local network address on WiFi LAN Adapter: 192.168.1.101. This could be 10.0.1.101. the result will change depending on your router
I use WSL on windows, and it has its own vEthernet address: 172.19.192.1
use host.docker.internal. Most answers have this or another form of it depending on OS. The name suggests it is now globally used by docker.
A third option is to use WAN address of the machine, or in other words IP given by the service provider. However, this may not work if IP is not static, and requires routing and firewall settings.
PS: Although pretty identical to this question here, and I posted this answer there, I first found this post, so I post it here too as may forget my own answer.
The simplest option that worked for me was,
I used the IP address of my machine on the local network(assigned by the router)
You can find this using the ifconfig command
e.g
ifconfig
en0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
options=400<CHANNEL_IO>
ether f0:18:98:08:74:d4
inet 192.168.178.63 netmask 0xffffff00 broadcast 192.168.178.255
media: autoselect
status: active
and then used the inet address. This worked for me to connect any ports on my machine.
When you have two docker images "already" created and you want to put two containers to communicate with one-another.
For that, you can conveniently run each container with its own --name and use the --link flag to enable communication between them. You do not get this during docker build though.
When you are in a scenario like myself, and it is your
docker build -t "centos7/someApp" someApp/
That breaks when you try to
curl http://172.17.0.1:localPort/fileIWouldLikeToDownload.tar.gz > dump.tar.gz
and you get stuck on "curl/wget" returning no "route to host".
The reason is security that is set in place by docker that by default is banning communication from a container towards the host or other containers running on your host.
This was quite surprising to me, I must say, you would expect the echosystem of docker machines running on a local machine just flawlessly can access each other without too much hurdle.
The explanation for this is described in detail in the following documentation.
http://www.dedoimedo.com/computers/docker-networking.html
Two quick workarounds are given that help you get moving by lowering down the network security.
The simplest alternative is just to turn the firewall off - or allow all. This means running the necessary command, which could be systemctl stop firewalld, iptables -F or equivalent.
I run docker with my private eth0m interface as explained here
I want to run docker without docker0 and 172.... interface
how to disable docker0?
Why would you remove docker0 ?
When Docker starts, it creates a virtual interface named docker0 on the host machine.
[...]
But docker0 is no ordinary interface. It is a virtual Ethernet bridge that automatically forwards packets between any other network interfaces that are attached to it. This lets containers communicate both with the host machine and with each other.
source:
https://docs.docker.com/articles/networking/
You need some bridge to run docker.
If you have another bridge for this, just delete default docker0.
Solution found.
First I configure my bridge0 via init scripts or NetworkManager,then
edit /etc/docker/daemon.json
{
"bridge": "bridge0"
}