disko can either be used after booting from a NixOS installer, or in conjunction with nixos-anywhere if you're installing remotely.

Before using disko, the specifications of the disks, partitions, type of formatting and the mount points must be defined in a Nix configuration. You can find examples of typical configurations in the Nix community repository, and use one of these as the basis of your own configuration.

You can keep your configuration and re-use it for other installations, or for a system rebuild.

disko is flexible, in that it supports most of the common formatting and partitioning options, including:

Disk layouts: GPT, MBR, and mixed.
Partition tools: LVM, mdadm, LUKS, and more.
Filesystems: ext4, btrfs, ZFS, bcachefs, tmpfs, and others.

It can work with these in various configurations and orders, and supports recursive layouts.

I erase my systems at every boot.

Over time, a system collects state on its root partition. This state lives in assorted directories like /etc and /var, and represents every under-documented or out-of-order step in bringing up the services.

“Right, run myapp-init.”

These small, inconsequential “oh, oops” steps are the pieces that get lost and don’t appear in your runbooks.

“Just download ca-certificates to … to fix …”

Each of these quick fixes leaves you doomed to repeat history in three years when you’re finally doing that dreaded RHEL 7 to RHEL 8 upgrade.

“Oh, touch /etc/ipsec.secrets or the l2tp tunnel won’t work.”

Setting up a new machine is time-consuming, and becomes complicated when it needs to be done remotely. If you're installing NixOS, the nixos-anywhere tool allows you to pre-configure the whole process including:

• Disk partitioning and formatting
• Configuring and installing NixOS
• Installing additional files and software

You can then initiate an unattended installation with a single CLI command. Since nixos-anywhere can access the new machine using SSH, it's ideal for remote installations.

Once you have initiated the command, there is no need to 'babysit' the installation. It all happens automatically.

You can use the stored configuration to repeat the same installation if you need to.