nixos-config/modules/initrd-ssh.nix

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# SPDX-FileCopyrightText: 2021-2023 Simon Bruder <simon@sbruder.de>
#
# SPDX-License-Identifier: AGPL-3.0-or-later
# To enable this on a host, you have to do the following:
# For network to work in initrd,
# either pass the `ip=` kernel parameter or enable networking.useDHCP.
# You also have to add the required kernel modules for the network adapter to `boot.initrd.availableKernelModules`
# (if it is not loaded by default).
# Then, you can set `boot.initrd.network.enable=true`,
# which enables networking in initrd.
# SSH in the initrd is enabled by this module automatically once networking is enabled.
# To be able to log in,
# you have to generate an SSH host key for the system (see the comments in the module on how to)
# and copy it to that host.
# It is then recommended to add a new `<host>-initrd`-entry to `modules/ssh.nix`
# to ensure the key is known and trusted by default on all other hosts.
# The host also needs a valid entry in `machines/default.nix`
# with `targetHost` set.
# If necessary, also set `unlockOverV4`,
# which forces the SSH connection to use IPv4
# (useful if the network of the host does not do SLAAC).
# If all that is done,
# remote unlocking should be possible by running `nix run .#unlock/host`
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{ config, lib, ... }:
{
boot.initrd.network = {
#enable = true;
ssh = {
enable = lib.mkDefault config.boot.initrd.network.enable;
port = 2222;
# ssh-keygen -t ed25519 -N "" -f ssh_host_ed25519_key_initrd -C HOSTNAME
# scp ssh_host_ed25519_key_initrd root@machine:/etc/ssh/
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hostKeys = [
"/etc/ssh/ssh_host_ed25519_key_initrd"
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];
};
};
# This only works for vfat (EFI),
# for ext2 (MBR) it needs to be changed manually with chmod.
fileSystems."/boot".options = lib.mkIf
(config.boot.initrd.network.ssh.enable && config.fileSystems."/boot".fsType == "vfat")
(lib.mkDefault [ "umask=0077" ]);
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}