alpine-tftp

MultiArch Alpine Linux + S6 + Trivial FTP(-hpa) Daemon

This image containerizes Trivial FTP daemon, providing a primitive but reliable file-access service intended to network-boot (or PXE) hosts. Checkout alpine-nfs for post-boot rootfs-serving needs.

Based on Alpine Linux from the s6 image with the tftp-hpa package installed in it.

Get the Image¶

Docker Hub

Pull the image from Docker Hub.

docker pull woahbase/alpine-tftp

Image Tags

The image is tagged respectively for the following architectures,

latest tag is annotated as multiarch so pulling without any tags should fetch the correct image for your architecture. Same goes for any of the version tags.

non-x86_64 builds have embedded binfmt_misc support and contain the qemu-user-static binary that allows for running it also inside an x86_64 environment that has support for it.

Run¶

Running the container starts the service.

docker run --rm \
  --name docker_tftp \
  -p 69:69/udp \
  -p 63050-63100/udp \
  -v $PWD/data:/data \
woahbase/alpine-tftp

Multi-Arch Support

If you want to run images for other architectures on a x86_64 machine, you will need to have binfmt support configured for your machine before running the image. multiarch, has made it easy for us containing that into a docker container, just run

docker run --rm --privileged multiarch/qemu-user-static --reset -p yes

Now images built for other architectures will also be executable. This is optional though, without the above, you can still run the image that is made for your architecture.

Configuration¶

We can customize the runtime behaviour of the container with the following environment variables.

ENV Vars	Default	Description
TFTP_ROOT	/data	Path to storage directory.
TFTPD_ARGS	--port-range 63050:63100 --secure $TFTP_ROOT	Customizable arguments passed to `in.tftp` service.
S6_NEEDED_PACKAGES	empty string	Space-separated list of extra APK packages to install on start. E.g. `"curl git tzdata"`
PUID	1000	Id of `S6_USER`.
PGID	100	Group id of `S6_USER`.
S6_USER	alpine	(Preset) Default non-root user for services to drop privileges to.
S6_USERHOME	/home/alpine	(Preset) HOME directory for `S6_USER`.

Did you know?

You can check your own UID/GID by running the command id in a terminal.

Also,

Recommended to use a remap-file to add further safety. E.g.

rg \\ /      # Convert backslashes to slashes
r ^[^/] /\0  # Convert non-absolute files
a ^/private/ # Reject requests for private dir
a \.pvt$     # Reject requests for private files
e ^/public/  # Allow access to  public files
# Add the remote IP address as a folder on the front of all requests.
# Essentially puts every request under its own IP jail. This way,
#  Any host can have its own fileset in its own directory by its IP, referenced by /
#  Only provisioned hosts can boot, other hosts unaffected
#  HostA cannot get HostB files
r ^ \i/

Checkout the docs to customize your own.

Stop the container with a timeout, (defaults to 2 seconds)

docker stop -t 2 docker_tftp

Restart the container with

docker restart docker_tftp

Removes the container, (always better to stop it first and -f only when needed most)

docker rm -f docker_tftp

Shell access¶

Get a shell inside a already running container,

docker exec -it docker_tftp /bin/bash

Optionally, login as a non-root user, (default is alpine)

docker exec -u alpine -it docker_tftp /bin/bash

Or set user/group id e.g 1000/100,

docker exec -u 1000:100 -it docker_tftp /bin/bash

Logs¶

To check logs of a running container in real time

docker logs -f docker_tftp

As-A-Service¶

Run the container as a service with the following as reference (and modify it as needed).

composenomad

With docker-compose (alpine-tftp.yml)

---
services:
  tftp:
    container_name: tftp
    deploy:
      resources:
        limits:
          cpus: '1.00'
          memory: 256M
      restart_policy:
        condition: on-failure
        delay: 10s
        max_attempts: 5
        window: 120s
    environment:
      PUID: ${PUID:-1000}
      PGID: ${PGID:-100}
      # TZ: ${TZ}
      TFTP_ROOT: /tftp
      TFTPD_ARGS: >-
        --address 0.0.0.0:${TFTP_PORT:-69}
        --port-range 63050:63100
        --secure
        /tftp/
      # --map-file /etc/tftpd.map
      # --verbose
      # -L4
    hostname: tftp
    image: woahbase/alpine-tftp:${TFTP_TAG:-latest}
    network_mode: host
    # ports:
    #   - protocol: udp
    #     host_ip: 0.0.0.0
    #     published: ${TFTP_PORT:-69}
    #     target: 69
    #
    #   - "63050-63100:63050-63100"
    volumes:
      - type: bind
        source: ${TFTP_DIR:?err}
        target: /tftp
        bind:
          create_host_path: false
      # - type: bind
      #   source: ${TFTP_DIR:?err}/configs/tftpd.map
      #   target: /etc/tftpd.map
      #   bind:
      #     create_host_path: false
      - type: bind
        source: /etc/localtime
        target: /etc/localtime
        read_only: true
        bind:
          create_host_path: false

With HashiCorp Nomad (alpine-tftp.hcl)

variables {
  dc   = "dc1" # to load the dc-local config file
  pgid = 100   # gid for docker
  puid = 1000  # uid for docker
  version = "5.2"
}
# locals { var = yamldecode(file("${var.dc}.vars.yml")) } # load dc-local config file

job "tftp" {
  datacenters = [var.dc]
  # namespace   = local.var.namespace
  priority    = 80
  # region      = local.var.region
  type        = "service"

  constraint { distinct_hosts = true }

  group "docker" {
    count = 1

    restart {
      attempts = 2
      interval = "2m"
      delay    = "15s"
      mode     = "fail"
    }
    update {
      max_parallel     = 1
      min_healthy_time = "10s"
      healthy_deadline = "3m"
      auto_revert      = false
    }

    service {
      name        = NOMAD_JOB_NAME
      port        = "tftp"
      tags        = ["ins${NOMAD_ALLOC_INDEX}", attr.unique.hostname]
      canary_tags = ["canary${NOMAD_ALLOC_INDEX}"]
    }

    ephemeral_disk { size = 128 } # MB
    network {
      # dns { servers = local.var.dns_servers }
      port "tftp"  { static = 69  }
      # port-range mapping unsupported in nomad
      # using host network anyway
      # port "range" { static = 63050-63100 }
    }
    volume "nomad-tftp-pxe" {
      type      = "host"
      read_only = false
      source    = "nomad-tftp-pxe"
    }

    task "tftp" {
      driver = "docker"

      config {
        healthchecks { disable = true }
        hostname     = NOMAD_JOB_NAME
        image        = "woahbase/alpine-tftp:${var.version}"
        network_mode = "host"
        ports        = ["tftp"]

        logging {
          type = "journald"
          config {
            mode = "non-blocking"
            tag = NOMAD_JOB_NAME
          }
        }

        mount {
          type     = "bind"
          source   = "local/tftpd.map"
          target   = "/etc/tftpd.map"
          readonly = true
        }
        mount {
          type     = "bind"
          target   = "/etc/localtime"
          source   = "/etc/localtime"
          readonly = true
        }
      }

      volume_mount {
        # ensure policies allow vault-generated-token to read-write to the volume
        volume      = "nomad-tftp-pxe"
        destination = "/tftp"
        read_only   = false
      }

      env {
        PUID = var.puid
        PGID = var.pgid
        # TZ   = local.var.tz

        TFTP_ROOT = "/tftp"
        TFTPD_ARGS  = "-L4 --address 0.0.0.0:69 --port-range 63050:63100 --secure --map-file /etc/tftpd.map -vvv /tftp/"
      }

      resources {
        cpu    = 512 # MHz
        memory = 256 # MB
      }

      template {
        change_mode = "restart"
        destination = "local/tftpd.map"
        perms       = "755"
        data        = <<-EOF
          # from: https://linux.die.net/man/8/in.tftpd
          rg \\ /      # Convert backslashes to slashes
          r ^[^/] /\0  # Convert non-absolute files
          a ^/private/ # Reject requests for private dir
          a \.pvt$     # Reject requests for private files
          e ^/public/  # Allow access to  public files
          # Add the remote IP address as a folder on the front of all requests.
          # Essentially puts every request under its own IP jail. This way,
          #  Any host can have its own fileset in its own directory by its IP, referenced by /
          #  Only provisioned hosts can boot, other hosts unaffected
          #  HostA cannot get HostB files
          r ^ \i/
        EOF
      }
    }
  }
}

Build Your Own¶

Feel free to clone (or fork) the repository and customize it for your own usage, build the image for yourself on your own systems, and optionally, push it to your own public (or private) repository.

Here's how...

Setting up¶

Before we clone the /repository, we must have Git, GNU make, and Docker (optionally, with buildx plugin for multi-platform images) setup on the machine. Also, for multi-platform annotations, we might require enabling experimental features of Docker.

Now, to get the code,

Github

Clone the repository with,

git clone https://github.com/woahbase/alpine-tftp
cd alpine-tftp

To get a list of all available targets, run

make help

Always Check Before You Make!

Did you know, we could check what any make target is going to execute before we actually run them, with

make -n <targetname> <optional args>

Build and Test¶

To create the image for your architecture, run the build and test target with

make build test

For building an image that targets another architecture, it is required to specify the ARCH parameter when building. e.g.

aarch64armhfarmv7lx86_64

make build test ARCH=aarch64

make build test ARCH=armhf

make build test ARCH=armv7l

make build test ARCH=x86_64

Build Parameters

All images have a few common build parameters that can be customized at build time, like

ARCH

The target architecture to build for. Defaults to host architecture, auto-detected at build-time if not specified. Also determines if binfmt support is required before build or run and runs the regbinfmt target automatically. Possible values are aarch64, armhf, armv7l, and x86_64.

BUILDDATE

The date of the build. Can be used to create separate tags for images. (format: yyyymmdd)

DOCKERFILE

The dockerfile to use for build. Defaults to the file Dockerfile, but if per-arch dockerfiles exist, (e.g. for x86_64 the filename would be Dockerfile_x86_64) that is used instead.

TESTCMD

The command to run for testing the image after build. Runs in a bash shell.

VERSION

The version of the app/tool, may need to be preset before starting the build (e.g. for binaries from github releases), or extracted from the image after build (e.g. for APK or pip packages).

REGISTRY

The registry to push to, defaults to the Docker Hub Registry (docker.io) or any custom registry that is set via docker configurations. Does not need to be changed for local or test builds, but to override, either pass it by setting an environment variable, or with every make command.

ORGNAME

The organization (or user) name under which the image repositories exist, defaults to woahbase. Does not need to be changed for local or test builds, but to override, either pass it by setting an environment variable, or with every make command.

The image may also require custom parameters (like binary architecture). Before you build, check the makefile for a complete list of parameters to see what may (or may not) need to be set.

BuildX and Self-signed certificates

If you're using a private registry (a-la docker distribution server) with self-signed certificates, that fail to validate when pulling/pushing images. You will need to configure buildx to allow insecure access to the registry. This is configured via the config.toml file. A sample is provided in the repository, make sure to replace YOUR.PRIVATE.REGISTRY with your own (include port if needed).

Make to Run¶

Running the image creates a container and either starts a service (for service images) or provides a shell (can be either a root-shell or usershell) to execute commands in, depending on the image. We can run the image with

make run

But if we just need a root-shell in the container without any fance pre-tasks (e.g. for debug or to test something bespoke), we can run bash in the container with --entrypoint /bin/bash. This is wrapped in the makefile as

make shell

Nothing vs All vs Run vs Shell

By default, if make is run without any arguments, it calls the target all. In our case this is usually mapped to the target run (which in turn may be mapped to shell).

There may be more such targets defined as per the usage of the image. Check the makefile for more information.

Push the Image¶

If the build and test steps finish without any error, and we want to use the image on other machines, it is the next step push the image we built to a container image repository (like /hub), for that, run the push target with

make push

If the built image targets another architecture then it is required to specify the ARCH parameter when pushing. e.g.

aarch64armhfarmv7lx86_64

make push ARCH=aarch64

make push ARCH=armhf

make push ARCH=armv7l

make push ARCH=x86_64

Pushing Multiple Tags

With a single make push, we are actually pushing 3 tags of the same image, e.g. for x86_64 architecture, they're namely

alpine-tftp:x86_64

The actual image that is built.

alpine-tftp:x86_64_(version)

It is expected that the application is versioned when built or packaged, it can be specified in the tag, this makes pulling an image by tag possible. Usually this is obtained from the parameter VERSION, which by default, is set by calling a function to extract the version string from the package installed in the container, or from github releases. Can be skipped with the parameter SKIP_VERSIONTAG to a non-empty string value like 1.

alpine-tftp:x86_64_(version)_(builddate)

When building multiple versions of the same image (e.g. for providing fixes or revisions), this ensures that a more recent push does not fully replace a previously pushed image. This way, although the architecture and version tags are replaced, it is possible to roll back to the previously built image by build date (format yyyymmdd). This value is obtained from the BUILDDATE parameter, and if not essential, can be skipped by setting the parameter SKIP_BUILDDATETAG to a non-empty string value like 1.

Pushing To A Private Registry

If you want to push the image to a custom registry that is not pre-configured on your system, you can set the REGISTRY variable either on the build environment, or as a makefile parameter, and that will be used instead of the default Docker Hub repository. Make sure to have push access set up before you actually push, and include port if needed. E.g.

export REGISTRY=your.private.registry:5000
make build test push

or

make build test push REGISTRY=your.private.registry:5000

Annotate Manifest(s)¶

For single architecture images, the above should suffice, the built image can be used in the host machine, and on other machines that have the same architecture too, i.e. after a push.

But for use-cases that need to support multiple architectures, there's a couple more things that need to be done. We need to create (or amend if already created beforehand) a manifest for the image(s) that we built, then annotate it to map the images to their respective architectures. And for our three tags created above we need to do it thrice.

Did you know?

We can inspect the manifest of any image by running

docker manifest inspect <imagename>:<optional tag, default is latest>

Tag Latest¶

Assuming we built the images for all supported architectures, to facilitate pulling the correct image for the architecture, we can create/amend the latest manifest and annotate it to map the tags :aarch64, :armhf, :armv7l, :x86_64 to the tag :latest by running

make annotate_latest

How it works

First we create or amend the manifest with the tag latest

createamend

docker manifest create \
woahbase/alpine-tftp:latest \
woahbase/alpine-tftp:aarch64 \
woahbase/alpine-tftp:armhf \
woahbase/alpine-tftp:armv7l \
woahbase/alpine-tftp:x86_64 \
;

docker manifest create --amend \
woahbase/alpine-tftp:latest \
woahbase/alpine-tftp:aarch64 \
woahbase/alpine-tftp:armhf \
woahbase/alpine-tftp:armv7l \
woahbase/alpine-tftp:x86_64 \
;

Then annotate the image for each architecture in the manifest with

aarch64armhfarmv7lx86_64

docker manifest annotate --os linux --arch arm64 \
    woahbase/alpine-tftp:latest \
    woahbase/alpine-tftp:aarch64;

docker manifest annotate --os linux --arch arm --variant v6 \
    woahbase/alpine-tftp:latest \
    woahbase/alpine-tftp:armhf;

docker manifest annotate --os linux --arch arm --variant v7 \
    woahbase/alpine-tftp:latest \
    woahbase/alpine-tftp:armv7l;

docker manifest annotate --os linux --arch amd64 \
    woahbase/alpine-tftp:latest \
    woahbase/alpine-tftp:x86_64;

And finally, push it to the repository using

docker manifest push -p woahbase/alpine-tftp:latest

Tag Version¶

Next, to facilitate pulling images by version, we create/amend the image-version manifest and annotate it to map the tags :aarch64_(version), :armhf_(version), :armv7l_(version), :x86_64_(version) to the tag :(version) by running

make annotate_version

How it works

First we create or amend the manifest with the tag (version)

createamend

docker manifest create \
woahbase/alpine-tftp:(version) \
woahbase/alpine-tftp:aarch64_(version) \
woahbase/alpine-tftp:armhf_(version) \
woahbase/alpine-tftp:armv7l_(version) \
woahbase/alpine-tftp:x86_64_(version) \
;

docker manifest create --amend \
woahbase/alpine-tftp:(version) \
woahbase/alpine-tftp:aarch64_(version) \
woahbase/alpine-tftp:armhf_(version) \
woahbase/alpine-tftp:armv7l_(version) \
woahbase/alpine-tftp:x86_64_(version) \
;

Then annotate the image for each architecture in the manifest with

aarch64armhfarmv7lx86_64

docker manifest annotate --os linux --arch arm64 \
    woahbase/alpine-tftp:(version) \
    woahbase/alpine-tftp:aarch64_(version);

docker manifest annotate --os linux --arch arm --variant v6 \
    woahbase/alpine-tftp:(version) \
    woahbase/alpine-tftp:armhf_(version);

docker manifest annotate --os linux --arch arm --variant v7 \
    woahbase/alpine-tftp:(version) \
    woahbase/alpine-tftp:armv7l_(version);

docker manifest annotate --os linux --arch amd64 \
    woahbase/alpine-tftp:(version) \
    woahbase/alpine-tftp:x86_64_(version);

And finally, push it to the repository using

docker manifest push -p woahbase/alpine-tftp:(version)

Tag Build-Date¶

Then, (optionally) we create/amend the (version)_(builddate) manifest and annotate it to map the tags :aarch64_(version)_(builddate), :armhf_(version)_(builddate), :armv7l_(version)_(builddate), :x86_64_(version)_(builddate) to the tag :(version)_(builddate) by running

make annotate_date

How it works

First we create or amend the manifest with the tag (version)_(builddate)

createamend

docker manifest create \
woahbase/alpine-tftp:(version)_(builddate) \
woahbase/alpine-tftp:aarch64_(version)_(builddate) \
woahbase/alpine-tftp:armhf_(version)_(builddate) \
woahbase/alpine-tftp:armv7l_(version)_(builddate) \
woahbase/alpine-tftp:x86_64_(version)_(builddate) \
;

docker manifest create --amend \
woahbase/alpine-tftp:(version)_(builddate) \
woahbase/alpine-tftp:aarch64_(version)_(builddate) \
woahbase/alpine-tftp:armhf_(version)_(builddate) \
woahbase/alpine-tftp:armv7l_(version)_(builddate) \
woahbase/alpine-tftp:x86_64_(version)_(builddate) \
;

Then annotate the image for each architecture in the manifest with

aarch64armhfarmv7lx86_64

docker manifest annotate --os linux --arch arm64 \
    woahbase/alpine-tftp:(version)_(builddate) \
    woahbase/alpine-tftp:aarch64_(version)_(builddate);

docker manifest annotate --os linux --arch arm --variant v6 \
    woahbase/alpine-tftp:(version)_(builddate) \
    woahbase/alpine-tftp:armhf_(version)_(builddate);

docker manifest annotate --os linux --arch arm --variant v7 \
    woahbase/alpine-tftp:(version)_(builddate) \
    woahbase/alpine-tftp:armv7l_(version)_(builddate);

docker manifest annotate --os linux --arch amd64 \
    woahbase/alpine-tftp:(version)_(builddate) \
    woahbase/alpine-tftp:x86_64_(version)_(builddate);

And finally, push it to the repository using

docker manifest push -p woahbase/alpine-tftp:(version)_(builddate)

That's all folks! Happy containerizing!

Maintenance¶

Sources at Github. Built and tested at home using Buildbot. Images at Docker Hub.

Maintained (or sometimes a lack thereof?) by WOAHBase.