I'm trying to make a Docker container accessible on e.g. 1.2.3.4:9999:99 from the Internet (so from outside the container) to be seen as the same IP from inside so when I'm inside the container and doing curl http://bot.whatismyipaddress.com/ I would get 1.2.3.4. I'm struggling with it for hours and no progress.
I'm running the container with docker run --name public254 -d -p 123.456.789.254:22:22 some-image:latest and it's accessible through 123.456.789.254 indeed. When inside it's seen as the main IP of the host as it's supposed to.
Now I want to modify this. What should I do next?
Well. I did it.
Enable forwarding
echo 1 > /proc/sys/net/ipv4/ip_forward
Find out container's internal IP
docker inspect -f '{{ .NetworkSettings.IPAddress }}' some_container
Route it correctly
iptables -t nat -I POSTROUTING -p all -s <container internal IP> -j SNAT --to-source <container external IP>
How can I connect to a docker container using its name instead of its IP address using the ping command?
ping <container_name> instead of ping <IP_address>
Check Network-scoped alias. It allows you to ping a container by its name.
ping $(docker inspect -f {{.NetworkSettings.IPAddress}} <container_name>)
I'm trying to get the IP address of my docker container as an environment variable within the container. Here is what I've tried:
When starting the container
docker run -dPi -e ip=`hostname -i` myDockerImage
When the container is already booted up
docker exec -it myDockerImage bash -c "export ip=`hostname -i`"
The problem with these two methods is that it uses the ip address of the host running the commands, not the docker container it's being run on.
So then I created a script inside the docker container that looks like this:
#!/bin/bash
export ip=`hostname -i`
echo $ip
And then run this with
docker exec -it myDockerImage bash -c ". ipVariableScript.sh"
When I add my_cmd which in my case is bash to the end of the script, it works in that one session of bash. I can't use it later in the files I need it in. I need to set it as an environment variable, not as a variable for one session.
So I already sourced it with the '.'. But it still won't echo when I'm in the container. If I put an echo $ip in the script, it will give me the correct IP address. But can only be used from within the script it's being set in.
Service names in Docker are more reliable and easier to use. However, here's
How to assign Docker guest IP to environment var inside guest
$ docker run -it ubuntu bash -c 'IP=$(hostname -i); echo ip=$IP'
ip=172.17.0.76
So, this is an old question but I ended up with the same question yesterday and my solution is this: use the docker internal option.
My containers were working fine but at some point the ip changed and I needed to change it on my docker-compose. Of course I can use the "docker network inspect my-container_default" and get my internal IP from that, but this also means changing my docker-compose every time the ip changes (and I'm still not that familiar with docker in order to detect IP changes automatically or make a more sofisticated config). So, I use the "host.docker.internal" flag. Now I no more need to check what's my IP from docker and everything is always connected.
Here an example of a node app which uses elastic search and needs to connect.
version: '3.7'
services:
api:
...configs...
depends_on:
- 'elasticsearch'
volumes:
- ./:/usr/local/api
ports:
- '3000:80'
links:
- elasticsearch:els
environment:
- PORT=80
- ELASTIC_NODE=http://host.docker.internal:9200
elasticsearch:
container_name: 'els'
image: docker.elastic.co/elasticsearch/elasticsearch:7.13.4
...elastic search container configs...
ports:
- '9200:9200'
expose:
- 9200
networks:
- elastic
networks:
elastic:
driver: bridge
Note the "ELASTIC_NODE=http://host.docker.internal:9200" on api environments and the "network" that the elastic search container is using (on bridge mode)
This way you don't need to worry about knowing your IP.
The container name is postgres in this example. It is a bit clumsy, but it delivers.
container_ip=$(docker inspect postgres -f "{{json .NetworkSettings.Networks }}" \
| awk -v FS=: '{print $9}' \
| cut -f1 -d\, \
| echo "${container_ip//\"}")
Make a function out of it:
#!/usr/bin/env bash
set -o errexit
set -o nounset
set -eu -o pipefail
#set -x
#trap read debug
#assign container ip address to variable
function get_container_ip () {
container_ip=$(docker inspect "$1" -f "{{json .NetworkSettings.Networks }}" \
| awk -v FS=: '{print $9}' \
| cut -f1 -d\,)
container_ip=$(echo "${container_ip//\"}")
}
get_container_ip $1
echo "$container_ip"
I have host with PostgreSQL and Docker container. PostgreSQL work on 5432 port. Docker container must connect to database. How to connect container with database through Dockerfile or run command? EXPOSE 5432 and docker run -p 5432:5432 ... did not help.
From the documentation page:
Sometimes you need to connect to the Docker host from within your
container. To enable this, pass the Docker host’s IP address to the
container using the --add-host flag. To find the host’s address, use
the ip addr show command.
$ HOSTIP=`ip -4 addr show scope global dev eth0 | grep inet | awk '{print \$2}' | cut -d / -f 1`
$ docker run --add-host=docker:${HOSTIP} --rm -it busybox telnet docker 5432
EXPOSE or -p flag work the other way around e.g. publish container ports to host which you don't want here.
I'm perfectly happy with the IP range that docker is giving me by default 176.17.x.x, so I don't need to create a new bridge, I just want to give my containers a static address within that range so I can point client browsers to it directly.
I tried using
RUN echo "auto eth0" >> /etc/network/interfaces
RUN echo "iface eth0 inet static" >> /etc/network/interfaces
RUN echo "address 176.17.0.250" >> /etc/network/interfaces
RUN echo "netmask 255.255.0.0" >> /etc/network/interfaces
RUN ifdown eth0
RUN ifup eth0
from a Dockerfile, and it properly populated the interfaces file, but the interface itself didn't change. In fact, running ifup eth0 within the container gets this error:
RTNETLINK answers: Operation not permitted Failed to bring up eth0
I have already answered this here
https://stackoverflow.com/a/35359185/4094678
but I see now that this question is actually older then the aforementioned one, so I'll copy the answer as well:
Easy with Docker version 1.10.1, build 9e83765.
First you need to create you own docker network (mynet123)
docker network create --subnet=172.18.0.0/16 mynet123
than simply run the image (I'll take ubuntu as example)
docker run --net mynet123 --ip 172.18.0.22 -it ubuntu bash
then in ubuntu shell
ip addr
Additionally you could use
--hostname to specify a hostname
--add-host to add more entries to /etc/hosts
Docs (and why you need to create a network) at https://docs.docker.com/engine/reference/commandline/network_create/
I'm using the method written here from the official Docker documentation and I have confirmed it works:
# At one shell, start a container and
# leave its shell idle and running
$ sudo docker run -i -t --rm --net=none base /bin/bash
root#63f36fc01b5f:/#
# At another shell, learn the container process ID
# and create its namespace entry in /var/run/netns/
# for the "ip netns" command we will be using below
$ sudo docker inspect -f '{{.State.Pid}}' 63f36fc01b5f
2778
$ pid=2778
$ sudo mkdir -p /var/run/netns
$ sudo ln -s /proc/$pid/ns/net /var/run/netns/$pid
# Check the bridge's IP address and netmask
$ ip addr show docker0
21: docker0: ...
inet 172.17.42.1/16 scope global docker0
...
# Create a pair of "peer" interfaces A and B,
# bind the A end to the bridge, and bring it up
$ sudo ip link add A type veth peer name B
$ sudo brctl addif docker0 A
$ sudo ip link set A up
# Place B inside the container's network namespace,
# rename to eth0, and activate it with a free IP
$ sudo ip link set B netns $pid
$ sudo ip netns exec $pid ip link set dev B name eth0
$ sudo ip netns exec $pid ip link set eth0 up
$ sudo ip netns exec $pid ip addr add 172.17.42.99/16 dev eth0
$ sudo ip netns exec $pid ip route add default via 172.17.42.1
Using this approach I run my containers always with net=none and set IP addresses with an external script.
Actually, despite my initial failure, #MarkO'Connor's answer was correct. I created a new interface (docker0) in my host /etc/network/interfaces file, ran sudo ifup docker0 on the host, and then ran
docker run --net=host -i -t ...
which picked up the static IP and assigned it to docker0 in the container.
Thanks!
This worked for me:
docker run --cap-add=NET_ADMIN -d -it myimages/image1 /bin/sh -c "/sbin/ip addr add 172.17.0.8 dev eth0; bash"
Explained:
--cap-add=NET_ADMIN have rights for administering the net (i.e. for the /sbin/ip command)
myimages/image1 image for the container
/bin/sh -c "/sbin/ip addr add 172.17.0.8 dev eth0 ; bash"
Inside the container run ip addr add 172.17.0.8 dev eth0 to add a new ip address 172.17.0.8 to this container (caution: do use a free ip address now and in the future). Then run bash, just to not have the container automatically stopped.
Bonus:
My target scene: setup a distributed app with containers playing different roles in the dist-app. A "conductor container" is able to run docker commands by itself (inside) so to start and stop containers as needed.
Each container is configured to know where to connect to access a particular role/container in the dist-app (so the set of ip's for each role must be known by each partner).
To do this:
"conductor container"
image created with this Dockerfile
FROM pin3da/docker-zeromq-node
MAINTAINER Foobar
# install docker software
RUN apt-get -yqq update && apt-get -yqq install docker.io
# export /var/run/docker.sock so we can connect it in the host
VOLUME /var/run/docker.sock
image build command:
docker build --tag=myimages/conductor --file=Dockerfile .
container run command:
docker run -v /var/run/docker.sock:/var/run/docker.sock --name=conductor1 -d -it myimages/conductor bash
Run containers with different roles.
First (not absolutely necessary) add entries to /etc/hosts to locate partners by ip or name (option --add-host)
Second (obviously required) assign a ip to the running container (use
/sbin/ip in it)
docker run --cap-add=NET_ADMIN --add-host worker1:172.17.0.8 --add-host worker2:172.17.0.9 --name=worker1 -h worker1.example.com -d -it myimages/image1 /bin/sh -c "/sbin/ip addr add 172.17.0.8 dev eth0; bash"
Docker containers by default do not have sufficient privileges to manipulate the network stack. You can try adding --cap-add=NET_ADMIN to the run command to allow this specific capability. Or you can try --privileged=true (grants all rights) for testing.
Another option is to use pipework from the host.
Setup your own bridge (e.g br0)
Start docker with: -b=br0
& with pipework (192.168.1.1 below being the default gateway ip address):
pipework br0 container-name 192.168.1.10/24#192.168.1.1
Edit: do not start with --net=none : this closes container ports.
See further notes
I understood that you are not looking at multi-host networking of containers at this stage, but I believe you are likely to need it soon. Weave would allow you to first define multiple container networks on one host, and then potentially move some containers to another host without loosing the static IP you have assigned to it.
pipework also great, but If you can use hostname other than ip then you can try this script
#!/bin/bash
# This function will list all ip of running containers
function listip {
for vm in `docker ps|tail -n +2|awk '{print $NF}'`;
do
ip=`docker inspect --format '{{ .NetworkSettings.IPAddress }}' $vm`;
echo "$ip $vm";
done
}
# This function will copy hosts file to all running container /etc/hosts
function updateip {
for vm in `docker ps|tail -n +2|awk '{print $NF}'`;
do
echo "copy hosts file to $vm";
docker exec -i $vm sh -c 'cat > /etc/hosts' < /tmp/hosts
done
}
listip > /tmp/hosts
updateip
You just need to run this command everytime you boot up your docker labs
You can find my scripts with additional function here dockerip
For completeness: there's another method suggested on the Docker forums. (Edit: and mentioned in passing by the answer from Андрей Сердюк).
Add the static IP address on the host system, then publish ports to that ip, e.g. docker run -p 192.0.2.1:80:80 -d mywebserver.
Of course that syntax won't work for IPv6 and the documentation doesn't mention that...
It sounds wrong to me: the usual wildcard binds (*:80) on the host theoretically conflict with the container. In practice the Docker port takes precedence and doesn't conflict, because of how it's implemented using iptables. But your public container IP will still respond on all the non-conflicting ports, e.g. ssh.
I discovered that --net=host might not always be the best option, as it might allow users to shut down the host from the container! In any case, it turns out that the reason I couldn't properly do it from inside was because network configuration was designed to be restricted to sessions that begun with the --privileged=true argument.
You can set up SkyDns with service discovery tool - https://github.com/crosbymichael/skydock
Or: Simply create network interface and publish docker container ports in it like here https://gist.github.com/andreyserdjuk/bd92b5beba2719054dfe