How to detect a docker daemon port

Question

I have installed Ubuntu and Docker  I am trying to launch Raik container     DOCKER RIAK AUTOMATIC CLUSTERING 1 DOCKER RAIK CLUSTER SIZE 5 DOCKER RIAK BACKEND leveldb make start-cluster   bin start   and get the error message      It looks like the environment variable DOCKER HOST has not been set     The Riak cluster cannot be started unless this has been set   appropriately   For example       export DOCKER HOST  tcp   127 0 0 1 2375    If I set   export DOCKER HOST  tcp   127 0 0 1 2375    all my other containers stop working and said  that can not find the Docker daemon   It looks like my Docker damon use other than 2375 port   How can I check it

User · Answer

Reference docs of docker  https   docs docker com install linux linux-postinstall  configure-where-the-docker-daemon-listens-for-connections    There are 2 ways in configuring the docker daemon port  1  Configuring at  etc default docker file   DOCKER OPTS  -H tcp   127 0 0 1 5000 -H unix    var run docker sock    2  Configuring at  etc docker daemon json      debug   true   hosts     tcp   127 0 0 1 5000    unix    var run docker sock       If the docker default socket is not configured Docker will wait for infinite period i e   Waiting for  var run docker sock Waiting for  var run docker sock Waiting for  var run docker sock Waiting for  var run docker sock Waiting for  var run docker sock   NOTE   BUT DON T CONFIGURE IN BOTH THE CONFIGURATION FILES  the following error may occur    Waiting for  var run docker sock unable to configure the Docker daemon with file  etc docker daemon json  the following directives are specified both as a flag and in the configuration file  hosts   from flag   tcp   127 0 0 1 5000 unix    var run docker sock   from file  tcp   127 0 0 1 5000    The reason for adding both the user port  tcp   127 0 0 1 5000  and default docker socket unix    var run docker sock  is that the user port enables the access to the docker APIs whereas the default socket enables the CLI  In case the default port unix    var run docker sock  is not mentioned in  etc default docker file the following error may occur     docker ps Cannot connect to the Docker daemon at unix    var run docker sock  Is the docker daemon running    This error is not because that the docker is not running  but because of default docker socket is not enabled   Once the configuration is enabled restart the docker service and verify the docker port is enabled or not     netstat -tunlp   grep -i 5000 tcp        0      0 127 0 0 1 5000          0 0 0 0                 LISTEN      31661 dockerd    Applicable for Docker Version 17 04  may vary with different versions of docker

User · Answer

By default  the docker daemon will use the unix socket unix    var run docker sock  you can check this is the case for you by doing a sudo netstat -tunlp and note that there is no docker daemon process listening on any ports   It s recommended to keep this setting for security reasons but it sounds like Riak requires the daemon to be running on a TCP socket   To start the docker daemon with a TCP socket that anybody can connect to  use the -H option   sudo docker -H 0 0 0 0 2375 -d  amp    Warning  This means machines that can talk to the daemon through that TCP socket can get root access to your host machine   Related docs   http   basho com posts technical running-riak-in-docker   https   docs docker com install linux linux-postinstall  configure-where-the-docker-daemon-listens-for-connections

User · Answer

Prepare extra configuration file  Create a file named  etc systemd system docker service d docker conf  Inside the file docker conf  paste below content     Service  ExecStart  ExecStart  usr bin dockerd -H tcp   0 0 0 0 2375 -H unix    var run docker sock      Note that if there is no directory like docker service d or a file named docker conf then you should create it     Restart Docker  After saving this file  reload the configuration by  systemctl daemon-reload and restart Docker by systemctl restart docker service   Check your Docker daemon   After restarting docker service  you can see the port in the output of  systemctl status docker service like  usr bin dockerd -H tcp   0 0 0 0 2375 -H unix    var run docker sock     Hope this may help  Thank you

User · Answer

Try add -H tcp   0 0 0 0 2375 at end of Execstart line  instead of -H 0 0 0 0 2375

User · Answer

Since I also had the same problem of  How to detect a docker daemon port  however I had on OSX and after little digging in I found the answer  I thought to share the answer here for people coming from osx    If you visit known-issues from docker for mac and github issue  you will find that by default the docker daemon only listens on unix socket  var run docker sock and not on tcp  The default port for docker is 2375  unencrypted  and 2376 encrypted  communication over tcp although you can choose any other port    On OSX its not straight forward to run the daemon on tcp port  To do this one way is to use socat container to redirect the Docker API exposed on the unix domain socket to the host port on OSX   docker run -d -v  var run docker sock  var run docker sock -p 127 0 0 1 2375 2375 bobrik socat TCP-LISTEN 2375 fork UNIX-CONNECT  var run docker sock   and then   export DOCKER HOST tcp   localhost 2375   However for local client on mac os you don t need to export DOCKER HOST variable to test the api

User · Answer

If you run ps -aux   dockerd you should see the tcp endpoint it is running on

[docker] How to detect a docker daemon port

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