Custom RancherOS ISO

It’s easy to build your own RancherOS ISO.

Create a clone of the main RancherOS repository to your local machine with a git clone.
```
$ git clone https://github.com/rancher/os.git
```
In the root of the repository, the “General Configuration” section of Dockerfile.dapper can be updated to use custom kernels, or custom Docker.
After you’ve saved your edits, run make in the root directory. After the build has completed, a ./dist/artifacts directory will be created with the custom built RancherOS release files.

Build Requirements: bash, make, docker (Docker version >= 1.10.3)
```
$ make
$ cd dist/artifacts
$ ls
initrd             rancheros.iso
iso-checksums.txt	vmlinuz
```

The rancheros.iso is ready to be used to boot RancherOS from ISO or launch RancherOS using Docker Machine.

Creating a GCE Image Archive

You can build the GCE image archive using Packer. You will need Packer, QEMU and GNU tar installed.

First, create gce-qemu.json:

{
 "builders":
 [
   {
     "type": "qemu",
     "name": "qemu-googlecompute",
     "iso_url": "https://github.com/rancher/os/releases/download/<RancherOS-Version>/rancheros.iso",
     "iso_checksum": "<rancheros.iso-MD5-hash>",
     "iso_checksum_type": "md5",
     "ssh_wait_timeout": "360s",
     "disk_size": 10000,
     "format": "raw",
     "headless": true,
     "accelerator": "none",
     "ssh_host_port_min": 2225,
     "ssh_host_port_max": 2229,
     "ssh_username": "rancher",
     "ssh_password": "rancher",
     "ssh_port": 22,
     "net_device": "virtio-net",
     "disk_interface": "scsi",
     "qemuargs": [
       ["-m", "1024M"], ["-nographic"], ["-display", "none"]
     ]
   }
 ],
 "provisioners": [
   {
     "type":"shell",
     "script": "../scripts/install2disk"
   }
 ]
}

NOTE: For faster builds You can use "kvm" as the accelerator field value if you have KVM, but that’s optional.

Run:

$ packer build gce-qemu.json

Packer places its output into output-qemu-googlecompute/packer-qemu-googlecompute - it’s a raw VM disk image. Now you just need to name it disk.raw and package it as sparse .tar.gz:

$ mv output-qemu-googlecompute/packer-qemu-googlecompute disk.raw
$ tar -czSf rancheros-<RancherOS-Version>.tar.gz disk.raw

NOTE: the last command should be using GNU tar. It might be named gtar on your system.