Packer base image

agent.pkr.hcl

source "docker" "alm" {
  image = "alm/base:20.04"
  pull = false # cause we previously built it
  commit = true
}

build {
  name = "agent"
  source "sources.docker.alm" {
    changes = []
    # that f*ckin' line which was supposed to be set to true BY DEFAULT
    # uncomment to make it work
    # fix_upload_owner = true 
  }
  provisioner "shell" {
    inline = [
      "echo Hello from Hell!"
    ]
    execute_command = "sudo sh -c '{{ .Vars }} {{ .Path }}'"
  }
  post-processor "docker-tag" {
    repository = "alm/agent"
    tags = [ "20.04" ]
  }
}

base.pkr.hcl

source "docker" "base" {
  image = "ubuntu:20.04"
  pull = false # already in cache
  commit = true
}

build {
  name = "base"
  source "sources.docker.base" {
    changes = [
      "USER johndoe" # run our 'base' image as johndoe
    ]
  }
  provisioner "shell" {
    inline = [ "apt-get update && apt-get install sudo -y" ] # cause sudo isn't in the base image. shame...
  }
  provisioner "shell" {
    inline = [ 
      "echo Hello from base!", 
      "groupadd -g 666 johndoe", # create johndoe group
      "useradd -r -m -u 666 -g 666 -G sudo johndoe && passwd -d johndoe", # create passwordless, sudoer user johndoe in the johndoe group
    ]
  }
  post-processor "docker-tag" {
    repository = "alm/base"
    tags = [ "20.04" ]
  }
}