Moving files in and out of a docker container

I recently stumbled across an old note I wrote about moving files in and out of Docker containers. It’s one of those commands I don’t use often enough to remember, but when I need it, I really need it.

So here’s a cleaned-up version for future me.

TL;DR

docker cp works much like the regular cp command. The only difference is that one side of the copy can be a Docker container.

# move file from host to a container
docker cp <file_path_in_host> <container_name_or_id>:<file_path_in_container>

# move file from container to a host
docker cp <container_name_or_id>:<file_path_in_container> <file_path_in_host>

A Practical Example

Let’s restore a sample PostgreSQL database inside a Docker container, create a backup, and then copy that backup back to the host.

Prerequisite

For this example, I already have a PostgreSQL 18 container running locally.

CONTAINER ID   IMAGE                COMMAND                  CREATED             STATUS             PORTS                                           NAMES
900ee02ff8eb   postgres:18-alpine   "docker-entrypoint.s…"   About an hour ago   Up About an hour   0.0.0.0:15432->5432/tcp, [::]:15432->5432/tcp   pg-swe-kata

I’ll be using the pg-swe-kata container throughout the rest of this guide.

• Download the sample database

  The PostgreSQL Tutorial from Neon provides a sample database called dvdrental.

  wget https://neon.com/postgresqltutorial/dvdrental.zip

• Copy the ZIP file into the container

  docker cp dvdrental.zip pg-swe-kata:dvdrental.zip

  The file is now available inside the container’s current working directory.

• Open a shell in the container and extract the archive

  docker exec -it pg-swe-kata bash
  unzip dvdrental.zip

• Create the database and restore it

  psql -U postgres
  CREATE DATABASE dvdrental;
  \q # exit psql

  Restore the database using pg_restore.

  pg_restore -U postgres -d dvdrental dvdrental.tar

• Verify the database was restored

  psql -U postgres
  \c dvdrental # connect to database
  \dt # list all tables
  \q # exit psql

• Create a database backup

  pg_dump -U postgres -W -F tar dvdrental -vf dvdrental_db_backup.tar

• Copy the backup back to the host

  docker cp pg-swe-kata:dvdrental_db_backup.tar dvdrental_db_backup.tar

That’s it.