nixos/scripts/bootstrap.sh

#!/usr/bin/env bash

echo -e "
Before using this tool, ensure that the host has been setup correctly.
Boot the latest Nixos-minimal install ISO on the host and access the tty.

Use 'ip a' to get the ip address, then 'sudo su' to change to root. Finally
Run 'passwd' and set a temporary password (something simple like '1234') 
for the root user.
"

read -p "Confirm host had been setup using the above steps...(yes|no): " confirm
[ "$confirm" != "yes" ] && echo "Exiting" && exit 0

hostname="sparky"
ip="192.168.122.192"
config="bootstrap"

# Delete key in known hosts if exists
sed -i "/$ip/d" ~/.ssh/known_hosts 

# Authorise source public key
echo "Copying pubkey to target host"
ssh-copy-id -i "$(readlink -f "$HOME/.ssh/id_ed25519.pub")" "root@$ip"

# Create temp directory for ssh keys to be copied to host:
temp=$(mktemp -d)

# Function to cleanup temporary directory on exit
cleanup() {
  rm -rf "$temp"
}
trap cleanup EXIT

# Create the directory where sshd expects to find the host keys
install -d -m755 "$temp/persist/etc/ssh"

# Create ssh keys if not exists
echo "Creating '$hostname' ssh keys"
ssh-keygen -t ed25519 -f "$temp/persist/etc/ssh/ssh_host_ed25519_key" -C root@"$hostname" -N ""

chmod 600 "$temp/persist/etc/ssh/ssh_host_ed25519_key"
chmod 644 "$temp/persist/etc/ssh/ssh_host_ed25519_key.pub"

# Generate age key from target host and user public ssh key
echo "Generating age key from target host and user ssh key"
HOST_AGE_KEY=$(nix-shell -p ssh-to-age --run "cat $temp/persist/etc/ssh/ssh_host_ed25519_key.pub | ssh-to-age")
echo -e "Host age key:\n$HOST_AGE_KEY\n"

# Update .sops.yaml with new age key:
SOPS_FILE="../nix-secrets/.sops.yaml"
sed -i "{
# Remove any * and & entries for this host
/[*&]$hostname/ d;
# Inject a new age: entry
# n matches the first line following age: and p prints it, then we transform it while reusing the spacing
/age:/{n; p; s/\(.*- \*\).*/\1$hostname/};
# Inject a new hosts: entry
/&hosts:/{n; p; s/\(.*- &\).*/\1$hostname $HOST_AGE_KEY/}
}" $SOPS_FILE

# Install Nixos to target
cd "$HOME/nixos"
git add . && git commit -m "auto: bootstrapping $hostname" && git push
[ $? != 0 ] && echo "Error commiting current changes" && exit 1

SHELL=/bin/sh nix run github:nix-community/nixos-anywhere -- --extra-files "$temp" --flake .#"$config" root@"$ip" -i "$HOME/.ssh/id_ed25519"
[ $? != 0 ] && echo "Error installing Nixos" && exit 1

## Delete keys from local known_hosts
echo "Deleting host from known_hosts"
sed -i "/$ip/d" ~/.ssh/known_hosts

# Check host OS has booted (and not booted back into live cd)
while true;
do
  read -p "Confirm live CD has been removed... (yes|no): " confirm
  [ "$confirm" = "yes" ] && break
done
echo "Waiting for $ip to come back online and port 22 to be open..."
while ! ping -c 1 $ip &> /dev/null || ! nc -zvw3 $ip 22 &> /dev/null
do
    echo "$ip is still offline or port 22 is not open. Checking again in 5 seconds..."
    sleep 5
done
echo "$ip is now online and port 22 is open!"

# Authorise source public key
echo "Copying pubkey to target host"
ssh-copy-id -i "$(readlink -f "$HOME/.ssh/id_ed25519.pub")" "root@$ip"

# Copy deploy_key to target for personal repo authorisation
scp -i "$(readlink -f "$HOME/.ssh/id_ed25519")" "$(readlink -f "$HOME/.ssh/deploy_key-ssh-ed25519")" "root@$ip:/persist/etc/ssh/deploy_key-ssh-ed25519"

ssh -i "$(readlink -f "$HOME/.ssh/id_ed25519")" "root@$ip" "nix-shell -p git --run 'git clone git@git.bitlab21.com:sam/nixos.git /persist/etc/nixos/'"

echo -e "###\nSuccessfully installed Nixos on the target host!\n###"

exit 0