---
description: |
  The `lxc` Packer builder builds containers for lxc1. The builder starts an LXC
  container, runs provisioners within this container, then exports the container
  as a tar.gz of the root file system.
page_title: LXC - Builders
---

# LXC Builder

Type: `lxc`
Artifact BuilderId: `ustream.lxc`

The `lxc` Packer builder builds containers for lxc1. The builder starts an LXC
container, runs provisioners within this container, then exports the container
as a tar.gz of the root file system.

The LXC builder requires a modern linux kernel and the `lxc` or `lxc1` package.
This builder does not work with LXD.

~> Note: to build Centos images on a Debian family host, you will need the
`yum` package installed. <br />Some provisioners such as `ansible-local` get
confused when running in a container of a different family. E.G. it will
attempt to use `apt-get` to install packages, when running in a Centos
container if the parent OS is Debian based.

## Basic Example

Below is a fully functioning example.

```json
{
  "builders": [
    {
      "type": "lxc",
      "name": "lxc-trusty",
      "config_file": "/tmp/lxc/config",
      "template_name": "ubuntu",
      "template_environment_vars": ["SUITE=trusty"]
    },
    {
      "type": "lxc",
      "name": "lxc-xenial",
      "config_file": "/tmp/lxc/config",
      "template_name": "ubuntu",
      "template_environment_vars": ["SUITE=xenial"]
    },
    {
      "type": "lxc",
      "name": "lxc-jessie",
      "config_file": "/tmp/lxc/config",
      "template_name": "debian",
      "template_environment_vars": ["SUITE=jessie"]
    },
    {
      "type": "lxc",
      "name": "lxc-centos-7-x64",
      "config_file": "/tmp/lxc/config",
      "template_name": "centos",
      "template_parameters": ["-R", "7", "-a", "x86_64"]
    }
  ]
}
```

## Configuration Reference

### Required:

- `config_file` (string) - The path to the lxc configuration file.

- `template_name` (string) - The LXC template name to use.

- `template_environment_vars` (array of strings) - Environmental variables to
  use to build the template with.

### Optional:

- `target_runlevel` (number) - The minimum run level to wait for the
  container to reach. Note some distributions (Ubuntu) simulate run levels
  and may report 5 rather than 3.

- `output_directory` (string) - The directory in which to save the exported
  tar.gz. Defaults to `output-<BuildName>` in the current directory.

- `container_name` (string) - The name of the LXC container. Usually stored
  in `/var/lib/lxc/containers/<container_name>`. Defaults to
  `packer-<BuildName>`.

- `command_wrapper` (string) - Allows you to specify a wrapper command, such
  as `ssh` so you can execute Packer builds on a remote host. Defaults to
  Empty.

- `init_timeout` (string) - The timeout in seconds to wait for the the
  container to start. Defaults to 20 seconds.

- `template_parameters` (array of strings) - Options to pass to the given
  `lxc-template` command, usually located in
  `/usr/share/lxc/templates/lxc-<template_name>`. Note: This gets passed as
  ARGV to the template command. Ensure you have an array of strings, as a
  single string with spaces probably won't work. Defaults to `[]`.

- `create_options` (array of strings) - Options to pass to `lxc-create`. For
  instance, you can specify a custom LXC container configuration file with
  `["-f", "/path/to/lxc.conf"]`. Defaults to `[]`. See `man 1 lxc-create` for
  available options.

- `start_options` (array of strings) - Options to pass to `lxc-start`. For
  instance, you can override parameters from the LXC container configuration
  file via `["--define", "KEY=VALUE"]`. Defaults to `[]`. See
  `man 1 lxc-start` for available options.

- `attach_options` (array of strings) - Options to pass to `lxc-attach`. For
  instance, you can prevent the container from inheriting the host machine's
  environment by specifying `["--clear-env"]`. Defaults to `[]`. See
  `man 1 lxc-attach` for available options.
