forked from mirrors/nixpkgs
47 lines
1.9 KiB
Markdown
47 lines
1.9 KiB
Markdown
# Building a NixOS (Live) ISO {#sec-building-image}
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Default live installer configurations are available inside `nixos/modules/installer/cd-dvd`.
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For building other system images, [nixos-generators] is a good place to start looking at.
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You have two options:
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- Use any of those default configurations as is
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- Combine them with (any of) your host config(s)
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System images, such as the live installer ones, know how to enforce configuration settings
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on wich they immediately depend in order to work correctly.
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However, if you are confident, you can opt to override those
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enforced values with `mkForce`.
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[nixos-generators]: https://github.com/nix-community/nixos-generators
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## Practical Instructions {#sec-building-image-instructions}
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```ShellSession
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$ git clone https://github.com/NixOS/nixpkgs.git
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$ cd nixpkgs/nixos
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$ nix-build -A config.system.build.isoImage -I nixos-config=modules/installer/cd-dvd/installation-cd-minimal.nix default.nix
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```
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To check the content of an ISO image, mount it like so:
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```ShellSession
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# mount -o loop -t iso9660 ./result/iso/cd.iso /mnt/iso
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```
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## Technical Notes {#sec-building-image-tech-notes}
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The config value enforcement is implemented via `mkImageMediaOverride = mkOverride 60;`
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and therefore primes over simple value assignments, but also yields to `mkForce`.
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This property allows image designers to implement in semantically correct ways those
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configuration values upon which the correct functioning of the image depends.
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For example, the iso base image overrides those file systems which it needs at a minimum
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for correct functioning, while the installer base image overrides the entire file system
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layout because there can't be any other guarantees on a live medium than those given
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by the live medium itself. The latter is especially true befor formatting the target
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block device(s). On the other hand, the netboot iso only overrides its minimum dependencies
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since netboot images are always made-to-target.
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