Ignition is the utility used by CoreOS Container Linux to manipulate disks during the initramfs. This includes partitioning disks, formatting partitions, writing files (regular files, systemd units, networkd units, etc.), and configuring users. On first boot, Ignition reads its configuration from a source of truth (remote URL, network metadata service, hypervisor bridge, etc.) and applies the configuration.
Odds are good that you don't want to invoke Ignition directly. In fact, it isn't even present in the Container Linux root filesystem. Take a look at the Getting Started Guide for details on providing Ignition with a runtime configuration.
Use the bug tracker to report bugs.