How to Connect an SFTP Client to a Dockerized Server

Kinkaku-ji, Japan, 2023

Recently, I joined a new business team to learn and handle some new technologies. One of my tasks involves fetching data from a database, generating a JSONLines file, and then sending it to the Bloomreach PATCH API via SFTP using a cron job. The repository has been under development for more than two years, but it lacks beginner-friendly documentation to explain what SFTP is or how it works within this project. After struggling for two days, I finally figured it out, and I want to share my experience here, along with a general use case example.

Steps:

1, Download the FileZilla Client from the official website.

2, Set Up an SFTP Server:

• Refer to this image to create and run an SFTP Server container from the docker hub: atmoz-sftp, if you want to know more about it, here is the GitHub repo.
• Generate an SSH key pair: Create a private key sftp_rsa and a public key sftp_rsa.pub. Store them in a directory, e.g., ~/Downloads/sftp/keys.
• Pull the Docker image, docker pull atmoz/sftp.
• Choose a hostname: use "foo" for the client and "19" as the port.

3, Run the Docker Container:

• Use the command below to start the docker container, mount the volumes to transfer the public key to the server, and share files between the localhost and Docker container:

docker run \
  -v ~/Downloads/sftp/keys/sftp_rsa.pub:/home/foo/.ssh/keys/sftp_rsa.pub:ro \
  -v ~/Downloads/share:/home/foo/share \
  -p 19:22 -d atmoz/sftp \
  foo::1001

4, Configure FileZilla Client:

• Start FileZilla Client: Go to File → Site Manager → My Sites (create a name) → General → Set the following:
• Protocol: SFTP
• Host: localhost
• Port: 19
• Logon type: Key file
• User: foo
• Key file: Browse and select the private key sftp_rsa
• Click Connect.

5, Verify Connection:

• You should see the message “Status: Directory listing of /share successful" in the FileZilla dashboard. The remote site /share folder should reflect the files from your local ~/Downloads/share folder.

6, Troubleshooting:

• If you encounter issues, use the following commands to check the status and logs of the Docker container:

docker ps
docker logs <CONTAINER ID>