coreos-installer

coreos-installer is a program to assist with installing Fedora CoreOS (FCOS) and Red Hat Enterprise Linux CoreOS (RHCOS). It can do the following:

Download and install the operating system to a target disk, optionally customizing it with an Ignition config or first-boot kernel parameters (coreos-installer install)
Download and verify an operating system image for various cloud, virtualization, or bare metal platforms (coreos-installer download)
List Fedora CoreOS images available for download (coreos-installer list-stream)
Embed an Ignition config in a live ISO image to customize the running system that boots from it (coreos-installer iso)

The options available for each subcommand are available via the --help option. This documentation will focus on how to obtain and run coreos-installer.

On Fedora CoreOS or RHEL CoreOS

coreos-installer is included in Fedora CoreOS and RHEL CoreOS. Just run coreos-installer from the command line. Fedora CoreOS provides live CD and network boot images you can run from RAM; you can use these to run coreos-installer to install Fedora CoreOS or RHEL CoreOS to disk.

On other Fedora editions

On other Fedora editions, you can install coreos-installer with DNF in the usual way:

sh sudo dnf install coreos-installer

Install with Cargo

You can also install coreos-installer with Rust's Cargo package manager:

sh cargo install coreos-installer

Run from a container

You can run coreos-installer from a container. You'll need to bind-mount /dev and /run/udev, as well as a data directory if you want to access files in the host. For example:

sh sudo podman run --pull=always --privileged --rm \ -v /dev:/dev -v /run/udev:/run/udev -v .:/data \ quay.io/coreos/coreos-installer:release \ install /dev/vdb -s testing -i /data/config.ign

Run from a live image using kernel command-line options

If you want a fully automated install, you can configure the Fedora CoreOS live CD or netboot image to run coreos-installer and then reboot the system. You do this by passing coreos.inst.<arg> arguments on the kernel command line.

Kernel command line options for coreos-installer running as a service

coreos.inst.install_dev - The block device on the system to install to, such as /dev/sda. Mandatory.
coreos.inst.stream - The Fedora CoreOS stream to install. Optional; defaults to stable unless coreos.inst.image_url is specified.
coreos.inst.image_url - The URL of the CoreOS image to install, overriding coreos.inst.stream. Optional.
coreos.inst.ignition_url - The URL of the Ignition config. Optional. If missing, no Ignition config will be embedded, which is probably not what you want.
coreos.inst.platform_id - The Ignition platform ID of the platform the CoreOS image is being installed on. Optional; defaults to metal. Normally this should be specified only if installing inside a virtual machine.
coreos.inst.insecure - Permit the OS image to be unsigned. Optional.
coreos.inst.skip_reboot - Don't reboot after installing. Optional.
coreos.inst.stream_base_url - Override the base URL of Fedora CoreOS stream metadata. Optional.

Installing from ISO

Download a Fedora CoreOS ISO image. The ISO image can install in either legacy boot (BIOS) mode or in UEFI mode. You can boot it in either mode, regardless of what mode the OS will boot from once installed.

Burn the ISO to disk and boot it, or use ISO redirection via a LOM interface. Alternatively you can use a VM like so:

virt-install --name cdrom --ram 4500 --vcpus 2 --disk size=20 --accelerate --cdrom /path/to/fedora-coreos-30.20191014.1-live.x86_64.iso --network default

Alternatively you can use qemu directly. Create a disk image to use as install target:

qemu-img create -f qcow2 fcos.qcow2 8G

Now, run the following qemu command:

qemu-system-x86_64 -accel kvm -name fcos -m 2048 -cpu host -smp 2 -netdev user,id=eth0,hostname=coreos -device virtio-net-pci,netdev=eth0 -drive file=/path/to/fcos.qcow2,format=qcow2 -cdrom /path/to/fedora-coreos-30.20191014.1-live.x86_64.iso

Once you have reached the boot menu, press <TAB> (isolinux) or e (grub) to edit the kernel command line. Add the parameters to the kernel command line telling it what you want it to do. For example:

coreos.inst.install_dev=/dev/sda
coreos.inst.stream=testing
coreos.inst.ignition_url=http://example.com/config.ign
coreos.inst.platform_id=qemu

Now press <ENTER> (isolinux) or <CTRL-x> (grub) to kick off the install.

The install will complete and eventually reboot the machine. After reboot the machine will boot into the installed system and the embedded Ignition config will run on first boot.

Installing from PXE

Download a Fedora CoreOS PXE kernel and initramfs image. The PXE image can install in either legacy boot (BIOS) mode or in UEFI mode. You can boot it in either mode, regardless of what mode the OS will boot from once installed.

Here is an example pxelinux.cfg for booting the installer images with PXELINUX:

DEFAULT pxeboot TIMEOUT 20 PROMPT 0 LABEL pxeboot KERNEL fedora-coreos-30.20191014.1-live-kernel-x86_64 APPEND ip=dhcp rd.neednet=1 initrd=fedora-coreos-30.20191014.1-live-initramfs.x86_64.img console=tty0 console=ttyS0 coreos.inst.install_dev=/dev/sda coreos.inst.stream=testing coreos.inst.ignition_url=http://192.168.1.101:8000/config.ign IPAPPEND 2

If you don't know how to use this information to test a PXE install you can start with something like these instructions for testing out PXE installs via a local VM + libvirt.

Build and test the installer for development

NOTE: The install subcommand writes directly to a block device (disk) and consumes the entire device. The device specified to the installer needs to be available and not currently in use. You cannot target a disk that is currently mounted.

Build coreos-installer and use it to install a Fedora CoreOS testing image to a partitionable loop device:

sh cargo build truncate -s 8G image-file sudo losetup -P /dev/loop0 image-file sudo target/debug/coreos-installer install /dev/loop0 -s testing