How to scan docker containers IPs from a docker container that is in the same network? - linux

Question

I am running multiple docker containers with docker-compose and all of them are in the same network.
Once the containers are up and running I would like to access from one of them to all the others through a shell script, where that script retrieves all IP addresses of the other containers from the docker network (first Ethernet interface eth0 inside the container).
I know there's a way to get IP addresses using container name, but I am running docker-compose with --scale flag so the script doesn't know how many containers are in that network, I am confused and don't know how to do that.
The base image of all containers is ubuntu:20.04

Answer 1

Since I couldn't find a simple way for now I created a script using nmap and ifconfig, it consists on getting the IP address of inet (Ethernet interface) from one of the docker machines then lookup on that network using nmap:
#!/bin/bash
EI=$(/sbin/ifconfig eth0 | grep inet | awk '{ print $2}') # Get inet IP of eth0
IPS=($(nmap $EI/24 | grep dindood | awk '{ print $6}' | sed 's/.$//; s/^.//')) # Look for the nodes Ip addresses
NAMES=($(nmap $EI/24 | grep dindood | awk '{ print $5}' | cut -f1 -d".")) # Look for the nodes Containers names
echo "host ip=$EI"
for i in "${!IPS[#]}"; do #loop through IP addresses found
echo "hostname= ${NAMES[$i]} | IP= ${IPS[$i]}"
done
the output looked like this for me:
host ip=192.168.160.3
hostname= my_project_container_2 | IP= 192.168.160.2
hostname= my_project_container_1 | IP= 192.168.160.4