SFTP (SSH File Transfer Protocol) server using OpenSSH

This project provides a Docker image for hosting a SFTP server. Included are Docker (docker-cli and docker-compose) and Kubernetes (kubectl and helm) deployment scripts

Supports architectures: amd64, arm and arm64

Support

If you need help or found a bug, please feel free to open an issue on the emberstack/docker-sftp GitHub project.

Usage

The SFTP server can be easily deployed to any platform that can host containers based on Docker. Below are deployment methods for:

• Docker CLI
• Docker-Compose
• Kubernetes using Helm (recommended for Kubernetes)

Process:

1. Create server configuration
2. Mount volumes as needed
3. Set host file for consistent server fingerprint

Configuration

The SFTP server uses a json based configuration file for default server options and to define users. This file has to be mounted on /app/config/sftp.json inside the container. Environment variable based configuration is not supported (see the Advanced Configuration section below for the reasons).

Below is the simplest configuration file for the SFTP server:

{
    "Global": {
        "Chroot": {
            "Directory": "%h",
            "StartPath": "sftp"
        },
        "Directories": ["sftp"]
    },
    "Users": [
        {
            "Username": "demo",
            "Password": "demo"
        }
    ]
}

This configuration creates a user demo with the password demo. A directory "sftp" is created for each user in the own home and is accessible for read/write. The user is chrooted to the /home/demo directory. Upon connect, the start directory is sftp.

You can add additional users, default directories or customize start directories per user. You can also define the UID and GID for each user. See the Advanced Configuration section below for all configuration options.

Deployment using Docker CLI

Simple Docker CLI run

$ docker run -p 22:22 -d emberstack/sftp --name sftp

This will start a SFTP in the container sftp with the default configuration. You can connect to it and login with the user: demo and password: demo.

Provide your configuration

$ docker run -p 22:22 -d emberstack/sftp --name sftp -v /host/sftp.json:/app/config/sftp.json:ro

This will override the default (/app/config/sftp.json) configuration with the one from the host /host/sftp.json.

Mount a directory from the host for the user 'demo'

$ docker run -p 22:22 -d emberstack/sftp --name sftp -v /host/sftp.json:/app/config/sftp.json:ro -v /host/demo:/home/demo/sftp

This will mount the demo directory from the host on the sftp directory for the "demo" user.

Deployment using Docker Compose

Simple docker-compose configuration

Create a docker-compose configuration file:

version: '3'
services:
  sftp:
    image: "emberstack/sftp"
    ports:
      - "22:22"
    volumes:
      - ../config-samples/sample.sftp.json:/app/config/sftp.json:ro

And run it using docker-compose

$ docker-compose -p sftp -f docker-compose.yaml up -d

The above configuration is available in the deploy\docker-compose folder in this repository. You can use it to start customizing the deployment for your environment.

Deployment to Kubernetes using Helm

Use Helm to install the latest released chart:

$ helm repo add emberstack https://emberstack.github.io/helm-charts
$ helm repo update
$ helm upgrade --install sftp emberstack/sftp

You can customize the values of the helm deployment by using the following Values:

Parameter	Description	Default
nameOverride	Overrides release name	""
fullnameOverride	Overrides release fullname	""
image.repository	Container image repository	emberstack/sftp
image.tag	Container image tag	latest
image.pullPolicy	Container image pull policy	Always if image.tag is latest, else IfNotPresent
storage.volumes	Defines additional volumes for the pod	{}
storage.volumeMounts	Defines additional volumes mounts for the sftp container	{}
configuration	Allows the in-line override of the configuration values	null
configuration.Global.Chroot.Directory	Global chroot directory for the sftp user group. Can be overriden per-user	"%h"
configuration.Global.Chroot.StartPath	Start path for the sftp user group. Can be overriden per-user	"sftp"
configuration.Global.Directories	Directories that get created for all sftp users. Can be appended per user	["sftp"]
configuration.Global.HostKeys.Ed25519	Set the server's ED25519 private key	""
configuration.Global.HostKeys.Rsa	Set the server's RSA private key	""
configuration.Users	Array of users and their properties	Contains demo user by default
configuration.Users[].Username	Set the user's username	N/A
configuration.Users[].Password	Set the user's password. If empty or null, password authentication is disabled	N/A
configuration.Users[].PasswordIsEncrypted	true or false. Indicates if the password value is already encrypted	false
configuration.Users[].AllowedHosts	Set the user's allowed hosts. If empty, any host is allowed	[]
configuration.Users[].PublicKeys	Set the user's public keys	[]
configuration.Users[].UID	Sets the user's UID.	null
configuration.Users[].GID	Sets the user's GID. A group is created for this value and the user is included	null
configuration.Users[].Chroot	If set, will override global Chroot settings for this user.	null
configuration.Users[].Directories	Array of additional directories created for this user	null
initContainers	Additional initContainers for the pod	{}
resources	Resource limits	{}
nodeSelector	Node labels for pod assignment	{}
tolerations	Toleration labels for pod assignment	[]
affinity	Node affinity for pod assignment	{}

Find us on Helm Hub

Advanced Configuration

TODO: This section is under development due to the number of configuration options being added. Please open an issue on the emberstack/docker-sftp project if you need help.