i try on my localhost recommended commands to learn playing with docker. The exact command is :
docker run -it --rm postgres psql
The error message i get is :
psql: error: connection to server on socket "/var/run/postgresql/.s.PGSQL.5432" failed: No such file or directory
Is the server running locally and accepting connections on that socket?
In fact the file .s.PGSQL.5432 does no exist in the container, while it exists on the host machine. So, what is wrong in my reasoning/command ?
You should think of containers as, conceptually, separate machines. Separate from the host and separate from each other.
When you run psql without any parameters, like you do here, it'll look for a postgres database running on the local machine, on port 5432. But since psql is running in a container it looks for the database inside the container. And there isn't one. That's what the error message is trying to tell you.
To get it to work, you need to specify the -h parameter on the psql command to tell it where the database is located. To get the address of the host machine, you can add --add-host=host.docker.internal:host-gateway to the docker run command. It's customary to call the host host.docker.internal.
So you end up with the command
docker run -it --rm --add-host=host.docker.internal:host-gateway postgres psql -h host.docker.internal
which should then let you connect to the postgres database on the host machine.
