Creating a Nix OS live CD

edit motivation

creating a modified NIXOS live CD out of a working nixos installation gives you the benefits:

verify what is included
no need to download it
it is easy to add your own programs to the image

edit how to build such an image

just run this command:

nix-build -A iso_minimal /etc/nixos/nixos/release.nix

once the building process is over, there will be a path like this:

/nix/store/2y4bivmrzg4d2dgby2b7prvfj7445088-nixos-iso-0.1pre1234/

use this command:

cat /nix/store/2y4bivmrzg4d2dgby2b7prvfj7445088-nixos-iso-0.1pre1234/nix-support/hydra-build-products 
file iso /nix/store/94rrfklbk2hcqhkr4627vsrlprlyva50-iso9660-image/iso/nixos-minimal-0.1pre1234-i686-linux-test.iso

and copy the new image from there.

edit adding additional software to the image

the basic script /etc/nixos/nixos/release.nix contains several entry points for custom images. as we are using -A iso_minimal have a look at: iso_minimal which will redirect us to:

./modules/installer/cd-dvd/installation-cd-minimal.nix -> /etc/nixos/nixos/modules/installer/cd-dvd/installation-cd-minimal.nix

# This module defines a small NixOS installation CD.  It does not
# contain any graphical stuff.
{config, pkgs, ...}:
{
  require = [
    ./installation-cd-base.nix
    ../../profiles/minimal.nix
  ];
}

edit step 1/3: starting ssh automatically in the image and adding a ssh key to it

setting a default password on the boot cdrom (so that nobody can login using the default 'unset' password: TODO

edit step 2/3: starting ssh automatically in the image and adding a ssh key to it

this is a hack, however it surely gives you an idea how to modify the stuff there:

in /etc/nixos/nixos/modules/installer/cd-dvd/installation-cd-base.nix add:

       mkdir -p /root/.ssh/
       echo 'ssh-rsa ssh-rsa  AAAAB3Nz...(cut here)...AzV foo@bar' > /root/.ssh/authorized_keys

at the end of

boot.postBootCommands =

edit step 3/3: starting ssh automatically in the image and adding a ssh key to it

THIS IS NOT WORKING YET: IGNORE LINES BELOW

vi /etc/nixos/nixos/modules/installer/cd-dvd/system-tarball-pc.nix

comment this line with a leading '#':

jobs.openssh.startOn = "network interfaces started";

edit software installation inside the 'once' deployed and booted image

in case you have booted from your image you can add software as described here:

install/remove software

Without NixOS you need to supply the source instead of /etc/nixos/nixos.

edit references

See also section "Building your own NixOS CD" of the NixOS manual.

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