# Reference Manual: disko ## Module Options We are currently having issues being able to generate proper module option documentation for our recursive disko types. However you can read the available options [here](https://github.com/nix-community/disko/tree/master/lib/types). Combined wit the [examples](https://github.com/nix-community/disko/tree/master/example) this hopefully gives you an overview. ## Command Line Options ``` Usage: ./disko [options] disk-config.nix or ./disko [options] --flake github:somebody/somewhere#disk-config With flakes, disk-config is discovered first under the .diskoConfigurations top level attribute or else from the disko module of a NixOS configuration of that name under .nixosConfigurations. Options: * -m, --mode mode set the mode, either format, mount or disko format: create partition tables, zpools, lvms, raids and filesystems mount: mount the partition at the specified root-mountpoint disko: first unmount and destroy all filesystems on the disks we want to format, then run the create and mount mode * -f, --flake uri fetch the disko config relative to this flake's root * --arg name value pass value to nix-build. can be used to set disk-names for example * --argstr name value pass value to nix-build as string * --root-mountpoint /some/other/mnt where to mount the device tree (default: /mnt) * --dry-run just show the path to the script instead of running it * --no-deps avoid adding another dependency closure to an in-memory installer requires all necessary dependencies to be available in the environment * --debug run with set -x ``` ## Generating Disk Images with Secrets Included using Disko Using Disko on NixOS allows you to efficiently create `.raw` VM images from a system configuration. The generated image can be used as a VM or directly written to a physical drive to create a bootable disk. Follow the steps below to generate disk images: ### Generating the `.raw` VM Image 1. **Create a NixOS configuration that includes the disko and the disk configuration of your choice** In the this example we create a flake containing a nixos configuration for `myhost`. ```nix # save this as flake.nix { description = "A disko images example"; inputs = { nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable"; disko.url = "github:nix-community/disko"; disko.inputs.nixpkgs.follows = "nixpkgs"; }; outputs = { self, disko, nixpkgs }: { nixosConfigurations.myhost = nixpkgs.lib.nixosSystem { system = "x86_64-linux"; modules = [ # You can get this file from here: https://github.com/nix-community/disko/blob/master/example/simple-efi.nix ./simple-efi.nix disko.nixosModules.disko ({ config, ... }: { # shut up state version warning system.stateVersion = config.system.nixos.version; # Adjust this to your liking. # WARNING: if you set a too low value the image might be not big enough to contain the nixos installation disko.devices.disk.vdb.imageSize = "10G"; }) ]; }; }; } ``` 2. **Build the disko image script:** Replace `myhost` in the command below with your specific system configuration name: ```console nix build .#nixosConfigurations.myhost.config.system.build.diskoImagesScript ``` 3. **Execute the disko image script:** Execute the generated disko image script. Running `./result --help` will output the available options: ```console ./result --help Usage: $script [options] Options: * --pre-format-files copies the src to the dst on the VM, before disko is run This is useful to provide secrets like LUKS keys, or other files you need for formating * --post-format-files copies the src to the dst on the finished image These end up in the images later and is useful if you want to add some extra stateful files They will have the same permissions but will be owned by root:root * --build-memory specify the ammount of memory that gets allocated to the build vm (in mb) This can be usefull if you want to build images with a more involed NixOS config By default the vm will get 1024M/1GB * --write-to-disk use an actuall disk instead of writing to a file This only works if your conifg has only one disk specified There is no check if the specified path is actually a disk so you can also write to another file ``` An example run may look like this: ``` sudo ./result --build-memory 2048 ``` The script will generate the actual image outside of the nix store in the current working directory. The create image names depend on the names used in `disko.disks` attrset in the NixOS configuration. In our code example it will produce the following image: ``` $ ls -la vdb.raw .rw-r--r-- root root 10 GB 2 minutes ago vdb.raw ``` ### Additional Configuration - For virtual drive use, define the image size in your Disko configuration: ```console disko.devices.disk..imageSize = "32G"; # Set your preferred size ``` - If the `.raw` image size is not optimal, use `--write-to-disk` to write directly to a drive. This bypasses the `.raw` file generation, which saves on read/write operations and is suitable for single disk setups. ### Understanding the Image Generation Process 1. Files specified in `--pre-format-files` and `--post-format-files` are temporarily copied to `/tmp`. 2. Files are then moved to their respective locations in the VM both before and after the Disko partitioning script runs. 3. The NixOS installer is executed, having access only to `--post-format-files`. 4. Upon installer completion, the VM is shutdown, and the `.raw` disk files are moved to the local directory. > **Note**: The auto-resizing feature is currently not available in Disko. > Contributions for this feature are welcomed. Adjust the `imageSize` > configuration to prevent issues related to file size and padding. By following these instructions and understanding the process, you can smoothly generate disk images with Disko for your NixOS system configurations.