Docker image using Packer - non-root user

[Alterego]

Hello

I'm new to packer, I've got the following packer script. I would like to create a docker ubuntu image with a non root user (ubuntu lets say). Further I would like add this user into the sudoers group.

I'm trying to adduser using shell provisioner but the build is failing with an error (note: I tried all flags possible but it's still giving me an error). 

How can I achieve this with Packer/Docker?

==> docker: Usage: useradd [options] LOGIN
==> docker:        useradd -D
==> docker:        useradd -D [options]
==> docker:
==> docker: Options:
==> docker:   -b, --base-dir BASE_DIR       base directory for the home directory of the
==> docker:                                 new account
==> docker:   -c, --comment COMMENT         GECOS field of the new account
==> docker:   -d, --home-dir HOME_DIR       home directory of the new account
==> docker:   -D, --defaults                print or change default useradd configuration
==> docker:   -e, --expiredate EXPIRE_DATE  expiration date of the new account
==> docker:   -f, --inactive INACTIVE       password inactivity period of the new account
==> docker:   -g, --gid GROUP               name or ID of the primary group of the new
==> docker:                                 account
==> docker:   -G, --groups GROUPS           list of supplementary groups of the new
==> docker:                                 account
==> docker:   -h, --help                    display this help message and exit
==> docker:   -k, --skel SKEL_DIR           use this alternative skeleton directory
==> docker:   -K, --key KEY=VALUE           override /etc/login.defs defaults
==> docker:   -l, --no-log-init             do not add the user to the lastlog and
==> docker:                                 faillog databases
==> docker:   -m, --create-home             create the user's home directory
==> docker:   -M, --no-create-home          do not create the user's home directory
==> docker:   -N, --no-user-group           do not create a group with the same name as
==> docker:                                 the user
==> docker:   -o, --non-unique              allow to create users with duplicate
==> docker:                                 (non-unique) UID
==> docker:   -p, --password PASSWORD       encrypted password of the new account
==> docker:   -r, --system                  create a system account
==> docker:   -R, --root CHROOT_DIR         directory to chroot into
==> docker:   -s, --shell SHELL             login shell of the new account
==> docker:   -u, --uid UID                 user ID of the new account
==> docker:   -U, --user-group              create a group with the same name as the user
==> docker:   -Z, --selinux-user SEUSER     use a specific SEUSER for the SELinux user mapping
==> docker:       --extrausers              Use the extra users database
==> docker:
==> docker: Killing the container: 2dc2bd524c302eaadb1f5e12ea72a19023ae6c02250138440f5191cf2f76dc43
Build 'docker' errored: Script exited with non-zero exit status: 2.Allowed exit codes are: [0]

Here's my simple json. file.

{
  "variables": {
    "repository": "ubuntu",
    "tag": "1.0",
    "root_password": null
  },
  "builders": [{
    "type": "docker",
    "author": "",
    "image": "ubuntu:latest",
    "commit": true,
    "changes": [
     "USER ubuntu"
    ]


  }],
  "provisioners": [
   {
     "type": "shell",
     "inline": [
       "apt-get update -y && apt-get install -y sudo",
       "sudo apt-get dist-upgrade -y && sudo apt-get autoremove -y && sudo apt clean -y && sudo apt-get install -y sudo bash-completion curl net-tools iputils-ping git python iptables",
       "sleep 15",
       "sudo groupadd -r ubuntu -g 901",
       "sudo useradd -D -u 901 -r -g ubuntu",
       "cd /tmp"
     
     ]


}],


  "post-processors": [
    {
      "type": "docker-tag",
      "repository": "{{user `repository`}}",
      "tag": "{{user `tag`}}"
    },
    {
  "type": "shell-local",
  "inline": ["echo foo"]
  }
  ]
}

Thanks

[Rickard von Essen]

useradd -D -u 901 -r -g ubuntu

Is incorrect, remove the -D. 

And it's a bit weird to make the ubuntu users system user, and give it a gui/uid < 1000.

Another style thing, it's a bit awkward to use sudo in front of every command when this is running as root. The only real reason to include sudo in a docker image is because there are some legacy scripts/software that uses it. 

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[Alterego]

Awesome it works.

{

 "variables": {

   "repository": "ubuntu",

   "tag": "1.0",

   "root_password": null

 },

 "builders": [{

   "type": "docker",

   "author": "",

   "image": "ubuntu:latest",

   "commit": true,

   "changes": [

    "USER ubuntu"

   ]

  }],

 "provisioners": [

  {

    "type": "shell",

    "inline": [

      "apt-get update -y && apt-get install -y sudo",

      "apt-get dist-upgrade -y && apt-get autoremove -y && apt clean -y && apt-get install -y bash-completion curl net-tools iputils-ping git python iptables",

      "sleep 15",

      "groupadd -r ubuntu",

      "useradd -r -g ubuntu ubuntu",