How to update etc hosts file in Docker image during docker build

Question

I want to update my  etc hosts file during  docker build    I added below line in Dockerfile but it s neither updating  etc hosts file nor giving any error   RUN echo  192 168 33 11    mynginx   gt  gt   etc hosts   I need to update  etc hosts  Can anyone suggest on this

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Complete Answer   Prepare your own hosts file you wish to add to docker container    1 2 3 4 abc tv 5 6 7 8 domain xyz 1 3 5 7 odd org 2 4 6 8 even net    COPY your hosts file into the container by adding the following line in the Dockerfile   COPY hosts  etc hosts extra    If you know how to use ENTRYPOINT or CMD or CRON job then incorporate the following command line into it or at least run this inside the running container     cat  etc hosts extra  gt  gt  etc hosts     You cannot add the following in the Dockerfile because the modification will be lost    RUN cat  etc hosts extra  gt  gt  etc hosts

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I m using AWS Elasticbeanstalk   Docker   Supervisord   Quick answer  Just add some code in Dockerfile   CMD echo 123 123 123 123 this is my host  gt  gt   etc hosts  supervisord -n

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Just a quick answer to run your container using   docker exec -it  lt container name gt   bin bash   once the container is open   cd      then   cd etc    and then you can  cat hosts   or   apt-get update apt-get vim   or any editor you like and open it in vim  here you can modify say your startup ip to 0 0 0 0

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Tis is me Dockefile FROM XXXXX ENV DNS 1  10 0 0 1 TEST1 COM  ENV DNS 1  10 0 0 1 TEST2 COM   CMD   bash   change hosts sh      cat change hosts sh su - root -c  env   grep DNS   akw -F       print  2    gt  gt   etc hosts     info user must su

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With a more recent version of docker  this could be done with docker-compose and its extra hosts directive  Add hostname mappings  Use the same values as the docker run client --add-host parameter  which should already be available for docker 1 8    extra hosts   -  quot somehost 162 242 195 82 quot   -  quot otherhost 50 31 209 229 quot   In short  modify  etc hosts of your container when running it  instead of when building it   With Docker 17 x   you have a docker build --add-host mentioned below  but  as commented in issue 34078 and in this answer   The --add-host feature during build is designed to allow overriding a host during build  but not to persist that configuration in the image   The solutions mentioned do refer the docker-compose I was suggesting above    Run an internal DNS  you can set the default DNS server to use in the daemon  that way every container started will automatically use the configured DNS by default    Use docker compose and provide a docker-compose yml to your developers  The docker compose file allows you to specify all the options that should be used when starting a container  so developers could just docker compose up to start the container with all the options they need to set

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I think docker recently added the --add-host flag to docker build which is really great    Edit  So this feature was updated on 17 04 0-ce  For more detail on how to use docker build with the --add-host flag please visit  https   docs docker com edge engine reference commandline build

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Since this still comes up as a first answer in Google I ll contribute possible solution   Command taken from here suprisingly worked for me  Docker 1 13 1  Ubuntu 16 04     docker exec -u 0  lt container-name gt   bin sh -c  echo   lt ip gt   lt name gt   gt  gt   etc hosts

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You can do with the following command at the time of running docker  docker run  OPTIONS  --add-host example com 127 0 0 1  lt your-image-name gt   lt your tag gt   Here I am mapping example com to localhost 127 0 0 1 and its working

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If this is useful for anyone  the HOSTALIASES env variable worked for me   echo  fakehost realhost   gt   etc host aliases export HOSTALIASES  etc host aliases

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You can not modify the host file in the image using echo in RUN step because docker daemon will maintain the file  etc hosts  and its content hosts entry  when you start a container from the image    However following can be used to achieve the same   ENTRYPOINT    bin sh    -c     echo 192 168 254 10   database-server  gt  gt   etc hosts  amp  amp  echo 192 168 239 62   redis-ms-server  gt  gt   etc hosts  amp  amp  exec java -jar   botblocker jar       Key to notice here is the use of exec command as docker documentation suggests  Use of exec will make the java command as PID 1 for the container  Docker interrupts will only respond to that    See https   docs docker com engine reference builder  entrypoint

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Following worked for me by mounting the file during docker run instead of docker build  docker service create --name  lt name gt   --mount type bind source  etc hosts dst  etc hosts    lt image gt

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You can use the --add-host option during docker run  For your case use  docker run --add-host   mynginx 192 168 33 11   image name   tag  This will update your  etc hosts you can check it by using following commands   docker exec -it  container id  sh  if sh doesnt work for you  then you can try bash or  bin sh or  bin bash  cd etc cat hosts

[docker] How to update /etc/hosts file in Docker image during "docker build"

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