How to set an environment variable in a running docker container

Question

If I have a docker container that I started a while back  what is the best way to set an environment variable in that running container  I set an environment variable initially when I ran the run command      docker run --name my-wordpress -e VIRTUAL HOST domain com --link my-mysql mysql -d spencercooley wordpress   but now that it has been running for a while I want to add another VIRTUAL HOST to the environment variable  I do not want to delete the container and then just re-run it with the environment variable that I want because then I would have to migrate the old volumes to the new container  it has theme files and uploads in it that I don t want to lose    I would just like to change the value of VIRTUAL HOST environment variable

User · Answer

You wrote that you do not want to migrate the old volumes  So I assume either the Dockerfile that you used to build the spencercooley wordpress image has VOLUMEs defined or you specified them on command line with the -v switch   You could simply start a new container which imports the volumes from the old one with the --volumes-from switch like     docker run --name my-new-wordpress --volumes-from my-wordpress -e VIRTUAL HOST domain com --link my-mysql mysql -d spencercooley wordpres   So you will have a fresh container but you do not loose the old data  You do not even need to touch or migrate it   A well-done container is always stateless  That means its process is supposed to add or modify only files on defined volumes  That can be verified with a simple docker diff  lt containerId gt  after the container ran a while   In that case it is not dangerous when you re-create the container with the same parameters  in your case slightly modified ones   Assuming you create it from exactly the same image from which the old one was created and you re-use the same volumes with the above mentioned switch    After the new container has started successfully and you verified that everything runs correctly you can delete the old wordpress container  The old volumes are then referred from the new container and will not be deleted

User · Answer

If you are running the container as a service using docker swarm  you can do   docker service update --env-add  lt you environment variable gt   lt service name gt   Also remove using --env-rm    To make sure it s addedd as you wanted  just run  docker exec -it  lt container id gt  env

User · Answer

Here s how you can modify a running container to update its environment variables  This assumes you re running on Linux  I tested it with Docker 19 03 8  Live Restore  First  ensure that your Docker daemon is set to leave containers running when it s shut down  Edit your  etc docker daemon json  and add  live-restore   true as a top-level key   sudo vim  etc docker daemon json   My file looks like this          default-runtime    nvidia        runtimes              nvidia                  path    nvidia-container-runtime                runtimeArgs                            live-restore   true     Taken from here   Get the Container ID  Save the ID of the container you want to edit for easier access to the files   export CONTAINER ID  docker inspect --format     Id     lt YOUR CONTAINER NAME gt     Edit Container Configuration  Edit the configuration file  go to the  Env  section  and add your key   sudo vim  var lib docker containers  CONTAINER ID config v2 json   My file looks like this        Env    TEST 1        Stop and Start Docker  I found that restarting Docker didn t work  I had to stop and then start Docker with two separate commands   sudo systemctl stop docker sudo systemctl start docker   Because of live-restore  your containers should stay up   Verify That It Worked  docker exec  lt YOUR CONTAINER NAME gt  bash -c  echo  TEST    Single quotes are important here   You can also verify that the uptime of your container hasn t changed   docker ps

User · Answer

For a somewhat narrow use case  docker issue 8838 mentions this sort-of-hack      You just stop docker daemon and change container config in  var lib docker containers  container-id  config json  sic    This solution updates the environment variables without the need to delete and re-run the container  having to migrate volumes and remembering parameters to run   However  this requires a restart of the docker daemon  And  until issue issue 2658 is addressed  this includes a restart of all containers

User · Answer

Use export VAR Value  Then type printenv in terminal to validate it is set correctly

User · Answer

To    set up many env  vars in one step  prevent exposing them in  sh  history  like with  -e  option  passing credentials api tokens      you can use     --env-file key value file txt   option   docker run --env-file key value file txt  INSTANCE ID

User · Answer

Docker doesn t offer this feature   There is an issue   How to set an enviroment variable on an existing container   8838   Also from  Allow docker start to take environment variables  7561       Right now Docker can t change the configuration of the container once it s created  and generally this is OK because it s trivial to create a new container

User · Answer

here is how to update a docker container config permanently   stop container  docker stop  lt container name gt  edit container config  docker run -it -v  var lib docker  var lib docker alpine vi   docker inspect --format   var lib docker containers    Id   config v2 json   lt container name gt   restart docker

User · Answer

I solve this problem with docker commit after some modifications in the base container  we only need to tag the new image and start that one docs docker com engine reference commandline commit  docker commit  container-id   tag    docker commit b0e71de98cb9 stack-overflow 0 0 1  then you can pass environment vars or file  docker run --env AWS ACCESS KEY ID --env AWS SECRET ACCESS KEY --env AWS SESSION TOKEN --env-file env local -p 8093 8093 stack-overflow 0 0 1

User · Answer

You could set an environment variable to a running Docker container by  docker exec -it -e  your environment Key   your new value   lt container gt   bin bash  Verify it using below command   printenv  This will update your key with the new value provided   Note  This will get reverted back to old on if docker gets restarted

User · Answer

Firstly you can set env inside the container the same way as you do on a linux box   Secondly  you can do it by modifying the config file of your docker container   var lib docker containers xxxx config v2 json   Note you need restart docker service to take affect  This way you can change some other things like port mapping etc

User · Answer

There are generaly two options  because docker doesn t support this feature now    Create your own script  which will act like runner for your command  For example      bin bash export VAR1 VAL1 export VAR2 VAL2 your cmd  Run your command following way   docker exec -i CONTAINER ID  bin bash -c  export VAR1 VAL1  amp  amp  export VAR2 VAL2  amp  amp  your cmd

[docker] How to set an environment variable in a running docker container

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