FTP Server for Local Development Environments

Disclaimer: This container was created with a local development environment in mind and therefore may not be very secure.

This Docker container implements a vsftpd server, with the following features:

• Debian:jesse base image.
• Virtual users with the ability to specify home directory and system user ID
• Passive mode

The compiled versions of this container can be found in the Docker registry.

Environment variables

This image uses environment variables to allow the configuration of some parameters at run time:

VSFTP_USER_[0-9]+

• Accepted values: A string in the format <username>:<password>:<system_uid>:<ftp_root_dir>. The <system_uid> and <ftp_root_dir> are optional, but the separating colons must still exist.
• Description: These are compound variables that allow for addition of any number of users.

Examples

• VSFTP_USER_1=hello:world:: - Create a user named hello with a password of world. The system user's UID will be the same as that of the built-in ftp account (UID: 104) and the FTP user's root directory will default to /home/virtual/hello.
• VSFTP_USER_1=user1:docker:33: - Create a user named user1 with a password of docker. The system user's UID will be 33 and the FTP user's root directory will default to /home/virtual/user1. If a system user with that ID already exists, vsftpd will tie that existing user to this user.
• VSFTP_USER_1=mysql:mysql:999:/srv/ftp/mysql - Create a user named mysql with a password of mysql. The system user's UID will be 999 and the FTP user's root directory will be set to /srv/ftp/mysql.

Caveats

• vsftpd apparently has special handling of an FTP user with the name ftp, so it's recommended to not use this name when defining an FTP user.

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PASV_ADDRESS

• Accepted values: DNS name or IP address that you use to FTP into this container.
• Description: This tells vsftpd which address to advertise to FTP clients as its address for passive connections. It's recommended to set this as an IP address since the container may not have the same DNS lookup settings as the Docker host.
• Note: If this is not specified, FTP communication most likely will not work as vsftpd will automatically use the IP of the interface on which the connection was received and that IP will usually be internal to the docker container.

Common Values

Environment	IP	Comment
Docker for Windows	10.0.75.1	Default Hyper-V host IP
boot2docker	192.168.99.100	Default docker-machine IP

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PASV_MIN_PORT

• Default value: 30000
• Accepted values: an integer less than PASV_MAX_PORT.
• Description: The minimum port to use for passive connections.

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PASV_MAX_PORT

• Default value: 30009
• Accepted values: an integer that is greater than PASV_MIN_PORT.
• Description: The minimum port to use for passive connections.

Ports

vsftpd is configured to listen on port 21. The container will need to open that port up as well as the range of passive ports (defaults of 30000-30009).

Volumes

By default, a user is given an FTP home directory of /home/virtual/${username}. Any volumes that you want a user to access should be mounted underneath the user's home folder.

Considerations

1. It's important that these are not mounted directly to the user's home directory but instead to a sub-directory of the user's home directory. The reason for this is because the user does not have write permissions in the root of their home directory.
2. Any folder that is mounted must already have the same permissions as the system user that the FTP user is operating under. So, if the we define a VSFTP_USER_1=user1:pass:33:, then the mounted folders must be owned by a user with ID of 33 for the FTP user to access it.

Named Volumes

Folders that are mounted directly from the host computer are orders of magnitude slower than named volumes. That is one of the reasons (a big one) to use named volumes instead of shared folders from the host.

Named volumes work nicely with this container. Docker supports the ability to mount the same named volumes to multiple containers at the same time. So, your application data is stored in a named volume and that same volume can be attached to this container to present FTP access to that data. That is one of the main reasons this container was created.

Example

  # create the volume
  docker volume create --name html-data
  
  # start the FTP daemon connected to the 'html-data' volume
  docker run --rm -d --name vsftpd \
       -v html-data:/home/virtual/hello/html \
       -e "PASV_ADDRESS=10.0.75.1" \
       -e "VSFTPD_USER_1=hello:world::" \
       -p "21:21" -p "30000-30009:30000-30009" \
       -t wildscamp/vsftpd
  
  # start the application that uses the 'html-data' volume
  docker run --rm -i --name webapp \
       -v html-data:/var/www/html \
       -t debian:jesse /bin/bash

You'll notice that both containers are given the same named volume but mounted in different locations. If one container changed something in the named volume, that change will be reflected in the other container.

Use cases

1. Spin up an the FTP server with a user named hello, password of world and mount a named volume under hello's FTP root directory:

  docker run --rm --name vsftpd -i \
    -v docker-html:/home/virtual/hello/html \
    -e "PASV_ADDRESS=10.0.75.1" \
    -e "VSFTPD_USER_1=hello:world::" \
    -p "21:21" -p "30000-30009:30000-30009" \
    -t wildscamp/vsftpd

2. Create multiple users with access to different volumes:

  docker run --rm --name vsftpd -i \
    -v docker-html:/home/virtual/hello/html \
    -v docker-mysql:/home/virtual/mysql/mysql \
    -e "PASV_ADDRESS=10.0.75.1" \
    -e "VSFTPD_USER_1=hello:world:33:" \
    -e "VSFTPD_USER_2=mysql:mysql:999:" \
    -p "21:21" -p "30000-30009:30000-30009" \
    -t wildscamp/vsftpd

User Environment Variables and Docker Compose

There is one special consideration regarding the VSFTPD_USER_[0-9]+ environment variables and Docker Compose. If you do not specify a root directory in a user configuration variable, the variable will end with a : and that has special meaning in a YAML file. In this case, it is necessary to define the environment variables using the dictionary method as demonstrated here.

  services:
    vsftpd:
      container_name: vsftpd
      image: wildscamp/vsftpd
      hostname: vsftpd
      ports:
        - "21:21"
        - "30000-30009:30000-30009"
      volumes:
        - docker-html:/home/virtual/www-data/html
        - docker-certificates:/home/virtual/certs/certs
        - docker-mysql:/home/virtual/mysql/mysql
      environment:
        PASV_ADDRESS: 10.0.75.1
        PASV_MIN_PORT: 30000
        PASV_MAX_PORT: 30009
        VSFTPD_USER_1: 'www-data:ftp:33:'
        VSFTPD_USER_2: 'mysql:mysql:999:'
        VSFTPD_USER_3: 'certs:certs:50:'