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Arpit Aggarwal
Arpit Aggarwal

Reputation: 29316

Docker - Not able to telnet Linked Container

I have a container A with Dockerfile as follows:

...
FROM ubuntu:latest
MAINTAINER arpitaggarwal "[email protected]"
EXPOSE 8080

and another container B with Dockerfile as follows:

...
FROM ubuntu:latest
MAINTAINER arpitaggarwal "[email protected]"
RUN apt-get install -q -y mysql-server
EXPOSE 3306

Then I started the container B using command:

docker run -P -it --name db B /bin/bash

And running the command: docker run --rm --name web --link db A env

gives me below output:

PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
HOSTNAME=a5dd66b72ca8
DB_PORT=tcp://172.17.0.2:3306
DB_PORT_3306_TCP=tcp://172.17.0.2:3306
DB_PORT_3306_TCP_ADDR=172.17.0.2
DB_PORT_3306_TCP_PORT=3306
DB_PORT_3306_TCP_PROTO=tcp
DB_NAME=/web/db
HOME=/root

Then I logged into container A and run the command: ping db

which gives me output:

PING db (172.17.0.2) 56(84) bytes of data.
64 bytes from db (172.17.0.2): icmp_seq=1 ttl=64 time=0.082 ms
64 bytes from db (172.17.0.2): icmp_seq=2 ttl=64 time=0.063 ms
64 bytes from db (172.17.0.2): icmp_seq=3 ttl=64 time=0.065 ms
64 bytes from db (172.17.0.2): icmp_seq=4 ttl=64 time=0.061 ms
64 bytes from db (172.17.0.2): icmp_seq=5 ttl=64 time=0.066 ms

And when I tried telnet command with port 3306, as follows:

telnet 172.17.0.2 3306

gives me output:

root@9b078c1fed82:/# telnet 172.17.0.2 3306
Trying 172.17.0.2...
telnet: Unable to connect to remote host: Connection refused

Any idea, how can I telnet linked container?

Any help will be appreciated!

Upvotes: 2

Views: 2482

Answers (2)

Arpit Aggarwal
Arpit Aggarwal

Reputation: 29316

After receiving the answer by @Andy Shinn, I Updated the container B Dockerfile as below:

FROM ubuntu:latest
MAINTAINER arpitaggarwal "[email protected]"
RUN apt-get install -q -y mysql-server
RUN apt-get install -q -y mysql-client
RUN sed -i -e"s/^bind-address\s*=\s*127.0.0.1/bind-address = 0.0.0.0/" /etc/mysql/my.cnf
EXPOSE 3306

And when I tried accessing mysql-server from container A as:

mysql -u root -ppassword -h 172.17.0.2

Gives me error:

ERROR 1130 (HY000): Host '172.17.0.3' is not allowed to connect to this MySQL server

Which I figured it out is because container A was trying to connect to db container through root user. But In mysql do not allow you to connect though root user remotely. So I work around creating another user in mysql-server with root privileges.

Upvotes: 1

Andy Shinn
Andy Shinn

Reputation: 28533

MySQL usually only listens on 127.0.0.1 by default. You need to modify the my.cnf during build and set bind-address to 0.0.0.0. You could accomplish this with something like:

RUN sed -i -e"s/^bind-address\s*=\s*127.0.0.1/bind-address = 0.0.0.0/" /etc/mysql/my.cnf

Upvotes: 2

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