Running a Docker container that accept traffic from the host

Question

I have the following config:
Dockerfile

FROM centos   MAINTAINER Eduar Tua <[email protected]>    RUN yum -y update && yum clean all RUN yum -y install httpd && yum clean all RUN echo "Apache works" >> /var/www/html/index.html  EXPOSE 80  ADD run-apache.sh /run-apache.sh RUN chmod -v +x /run-apache.sh  CMD ["/run-apache.sh"] 

The run-apache.sh script:

#!/bin/bash  rm -rf /run/httpd/* /tmp/httpd*  exec /usr/sbin/apachectl -D FOREGROUND 

Then I build the image with:

sudo docker build --rm -t platzi/httpd .   

then

sudo docker run -d -p 80:80 platzi/httpd 

After that when I try to run the container accepting connections from the host in the 80 port I get this:

67ed31b50133adc7c745308058af3a6586a34ca9ac53299d721449dfa4996657 FATA[0002] Error response from daemon: Cannot start container     67ed31b50133adc7c745308058af3a6586a34ca9ac53299d721449dfa4996657: Error starting userland proxy: listen tcp 0.0.0.0:80: bind: address already in use 

Any help?

Answer 1

It is saying port 80 is busy ... run this to see who is using port 80

sudo netstat -tlnp | grep 80 # sudo apt-get install net-tools # to install netstat  tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN      1380/nginx -g daemo tcp6       0      0 :::80                   :::*                    LISTEN      1380/nginx -g daemo 

scroll to far right to see offending PID of process holding port 80 ... its PID 1380 so lets do a process list to see that pid

ps -eaf | grep 1380  root      1380     1  0 11:33 ?        00:00:00 nginx: master process /usr/sbin/nginx -g daemon on; master_process on; 

so teardown that offending process to free up the port 80

sudo kill 1380  # if you know the pid ( 1380 for example ) 

__ or __

sudo fuser -k 80/tcp #  just kill whatever pid is using port 80 tcp 

If after doing above its still saying busy then probably the process which you killed got auto relaunched in which case you need to kill off its watcher however you can walk up the process tree from netstat output to identify this parent process and kill that too

Here is how to identify the parent pid of a given process pid

ps -eafww  eve         2720    2718  0 07:56 ?        00:00:00 /usr/share/skypeforlinux/skypeforlinux --type=zygote 

in above pid is 2720 and its parent will be the next column to right pid 2718 ... there are commands to show a process tree to visualize these relationships

ps -x --forest   

or

pstree  -p 

with sample output of

systemd(1)─┬─ModemManager(887)─┬─{ModemManager}(902)            │                   └─{ModemManager}(906)            ├─NetworkManager(790)─┬─{NetworkManager}(872)            │                     └─{NetworkManager}(877)            ├─accounts-daemon(781)─┬─{accounts-daemon}(792)            │                      └─{accounts-daemon}(878)            ├─acpid(782)            ├─avahi-daemon(785)───avahi-daemon(841)            ├─colord(1471)─┬─{colord}(1472)            │              └─{colord}(1475)            ├─containerd(891)─┬─containerd-shim(1836)─┬─registry(1867)─┬─{registry}(1968)            │                 │                       │                ├─{registry}(1969)            │                 │                       │                ├─{registry}(1970)