The network ports of the container need to be configurable

[KamranAzeem]

There are times when this container image may be used to troubleshoot another container by making it part of the same IP namespace (i.e. two or more containers sharing the same IP address). In case any of the container runs a web server, such as regular nginx container (not alpine version), then multitool cannot join the same container.

Example:

[kamran@kworkhorse network-multitool]$ docker run --name nginx -d nginx
6e8b6ed8bfa67f6b7119804f2217e46d8c5ebecd0dd4b6ec6bc5099f2ebe60c4

[kamran@kworkhorse network-multitool]$ docker ps
CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS              PORTS               NAMES
6e8b6ed8bfa6        nginx               "nginx -g 'daemon of…"   2 seconds ago       Up 1 second         80/tcp              nginx

[kamran@kworkhorse network-multitool]$ docker exec -it nginx sh
# netstat -ntlp
sh: 1: netstat: not found
# ifconfig
sh: 2: ifconfig: not found
# curl localhost
sh: 3: curl: not found
# exit
[kamran@kworkhorse network-multitool]$

[kamran@kworkhorse network-multitool]$ docker run --name multitool --net container:nginx -d praqma/network-multitool 
17afa2eda1c43d6787975bcfdb4d3ace9044a72c0d38a7d74d65827779a7a774
[kamran@kworkhorse network-multitool]$

[kamran@kworkhorse network-multitool]$ docker ps
CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS              PORTS               NAMES
6e8b6ed8bfa6        nginx               "nginx -g 'daemon of…"   3 minutes ago       Up 3 minutes        80/tcp              nginx
[kamran@kworkhorse network-multitool]$ 



[kamran@kworkhorse network-multitool]$ docker ps -a
CONTAINER ID        IMAGE                      COMMAND                  CREATED             STATUS                      PORTS               NAMES
17afa2eda1c4        praqma/network-multitool   "/docker-entrypoint.…"   30 seconds ago      Exited (1) 26 seconds ago                       multitool
6e8b6ed8bfa6        nginx                      "nginx -g 'daemon of…"   3 minutes ago       Up 3 minutes                80/tcp              nginx

[kamran@kworkhorse network-multitool]$ 


[kamran@kworkhorse network-multitool]$ docker logs multitool 
2019/07/29 11:08:08 [emerg] 13#13: bind() to 0.0.0.0:80 failed (98: Address in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address in use)
2019/07/29 11:08:08 [emerg] 13#13: bind() to 0.0.0.0:80 failed (98: Address in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address in use)
2019/07/29 11:08:08 [emerg] 13#13: bind() to 0.0.0.0:80 failed (98: Address in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address in use)
2019/07/29 11:08:08 [emerg] 13#13: bind() to 0.0.0.0:80 failed (98: Address in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address in use)
2019/07/29 11:08:08 [emerg] 13#13: bind() to 0.0.0.0:80 failed (98: Address in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address in use)
2019/07/29 11:08:08 [emerg] 13#13: still could not bind()
nginx: [emerg] still could not bind()
[kamran@kworkhorse network-multitool]$ 

This means the port of the container needs to be configurable at run time , using some "port modifier directive"/"environment variables". It should serve on default ports 80 and 443 if port modifier directives are not present.