Add initial QVM CLI, Nix flake, scripts and README

bin/qvm-rebuild

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+#!/usr/bin/env bash
+#
+# qvm-rebuild - Build the base qcow2 image from user's flake
+#
+# This script builds the QVM base image by:
+# - Ensuring a user flake exists (copying default if needed)
+# - Running nix build on the user's flake configuration
+# - Copying the resulting qcow2 to the base image location
+# - Optionally warning if VM is running
+#
+
+set -euo pipefail
+
+# Source common library
+QVM_LIB_DIR="${QVM_LIB_DIR:-$(dirname "$(readlink -f "$0")")/../lib}"
+# shellcheck source=lib/common.sh
+source "$QVM_LIB_DIR/common.sh"
+
+#
+# ensure_user_flake - Ensure user's flake exists, copy default if missing
+#
+ensure_user_flake() {
+    if [[ -f "$QVM_USER_FLAKE/flake.nix" ]]; then
+        log_info "Using existing user flake: $QVM_USER_FLAKE/flake.nix"
+        return 0
+    fi
+    
+    log_info "User flake not found, copying default template..."
+    
+    # Determine default flake location
+    # In installed version: $QVM_LIB_DIR/../flake/default-vm/
+    # In development: $(dirname "$0")/../flake/default-vm/
+    local default_flake_dir="$QVM_LIB_DIR/../flake/default-vm"
+    
+    if [[ ! -d "$default_flake_dir" ]]; then
+        die "Default flake template not found at: $default_flake_dir"
+    fi
+    
+    if [[ ! -f "$default_flake_dir/flake.nix" ]]; then
+        die "Default flake.nix not found at: $default_flake_dir/flake.nix"
+    fi
+    
+    # Create user flake directory and copy template
+    mkdir -p "$QVM_USER_FLAKE"
+    cp -r "$default_flake_dir"/* "$QVM_USER_FLAKE/"
+    
+    log_info "Default flake copied to: $QVM_USER_FLAKE"
+    echo ""
+    echo "You can customize your VM by editing: $QVM_USER_FLAKE/flake.nix"
+    echo ""
+}
+
+#
+# build_base_image - Build the base image using nix
+#
+build_base_image() {
+    log_info "Building base image from flake..."
+    
+    # Build the qcow2 output from user's flake
+    local build_result="$QVM_STATE_DIR/result"
+    
+    if ! nix build "$QVM_USER_FLAKE#qcow2" --out-link "$build_result"; then
+        die "Failed to build base image. Check your flake configuration at: $QVM_USER_FLAKE/flake.nix"
+    fi
+    
+    # Verify the result contains nixos.qcow2
+    local qcow2_path="$build_result/nixos.qcow2"
+    if [[ ! -f "$qcow2_path" ]]; then
+        die "Build succeeded but nixos.qcow2 not found at: $qcow2_path"
+    fi
+    
+    # Copy the qcow2 to base image location
+    log_info "Copying image to: $QVM_BASE_IMAGE"
+    cp -L "$qcow2_path" "$QVM_BASE_IMAGE"
+    
+    # Remove the result symlink
+    rm -f "$build_result"
+    
+    # Get image size for informational output
+    local image_size
+    image_size=$(du -h "$QVM_BASE_IMAGE" | cut -f1)
+    
+    log_info "Base image built successfully"
+    echo ""
+    echo "Base image: $QVM_BASE_IMAGE"
+    echo "Image size: $image_size"
+}
+
+#
+# warn_if_running - Warn user if VM is currently running
+#
+warn_if_running() {
+    if is_vm_running; then
+        log_warn "VM is currently running"
+        echo ""
+        echo "The new base image will only take effect after restarting the VM:"
+        echo "  qvm stop"
+        echo "  qvm start"
+        echo ""
+        echo "Note: Changes to your VM overlay will be preserved."
+        echo "      Use 'qvm reset' to start fresh with the new base image."
+        echo ""
+    fi
+}
+
+#
+# main - Main execution flow
+#
+main() {
+    log_info "Rebuilding QVM base image..."
+    
+    # Ensure required directories exist
+    ensure_dirs
+    
+    # Ensure user has a flake configuration
+    ensure_user_flake
+    
+    # Build the base image
+    build_base_image
+    
+    # Warn if VM is running
+    warn_if_running
+    
+    # Print next steps
+    echo "Next steps:"
+    if is_vm_running; then
+        echo "  1. Stop the VM: qvm stop"
+        echo "  2. Start the VM: qvm start"
+    else
+        echo "  - Start the VM: qvm start"
+    fi
+    echo "  - Customize the VM: edit $QVM_USER_FLAKE/flake.nix"
+    echo "  - Reset to fresh state: qvm reset"
+}
+
+# Run main function
+main "$@"