How to execute docker exec commande inside a docker container

Question

I execute a command inside a docker container :

docker exec -i nullmailer sendmail -f username@gmail.com

The container response is :

the docker command does not exist.

How to execute docker exec command inside a docker container ?

Answer 1

If your containers are running on the same host, you can run docker commands inside the container, by exposing the docker socket to the container.

To achieve this, when running the container, mount the docker.sock as such:

docker run -v /var/run/docker.sock:/var/run/docker.sock ...

Now you can execute docker commands from within the container.

Comments

And for Windows it is:

`docker run -v //var/run/docker.sock:/var/run/docker.sock ...`

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Hi @Werner, Can you put this up as an answer? It'll be helpful for other readers. Thank you!

Answer 2

You need to get inside the container and then try to execute your command

Follow these steps:

• Use docker ps to get the name of the existing container

• Use the command docker exec -it <container name> /bin/bash to get a bash shell in the container

• Or directly use docker exec -it <container name> <command> to execute whatever command you specify in the container.

Comments

I am doing this same thing but it isn't working when I have a date variable in it. Have any ideas on how to get this to work? I want to be able to run it from a crontab. 

docker exec -it docker-partkeepr_database_1 bash -c mysqldump --databases partkeepr -upartkeepr -pUSERPASSWORD  > /var/lib/mysql/backup/partkeeprsql.$(date +%Y-%m-%d-%H.%M.%S).sql

It comes back saying -bash: /var/lib/mysql/backup/partkeeprsql.$(date +%Y-%m-%d-%H.%M.%S).sql: No such file or directory

Yet when I run the command mysqldump --databases partkeepr -upartkeepr -pUSERPASSWORD  > /var/lib/mysql/backup/partkeeprsql.$(date +%Y-%m-%d-%H.%M.%S).sql 

after having already done a docker exec -it docker-partkeepr_database_1 bash command to get into the container it runs just fine and puts the date on it.  

Any suggestions? 

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Hi,

I think you need to pass your command in a quote. Try with the below command once.

docker exec -it docker-partkeepr_database_1 bash -c "mysqldump --databases partkeepr -upartkeepr -pUSERPASSWORD  > /var/lib/mysql/backup/partkeeprsql.$(date +%Y-%m-%d-%H.%M.%S).sql"