nixos-rebuild: Add ‘dry-activate’ command

‘nixos-rebuild dry-activate’ builds the new configuration and then
prints what systemd services would be stopped, restarted etc. if the
configuration were actually activated. This could be extended later to
show other activation actions (like uids being deleted).

To prevent confusion, ‘nixos-rebuild dry-run’ has been renamed to
‘nixos-rebuild dry-build’.

1 files changed, 6 insertions, 5 deletions

diff --git a/nixos/modules/installer/tools/nixos-rebuild.sh b/nixos/modules/installer/tools/nixos-rebuild.sh
index 8157f8fc7da5..1d6df8cb3f71 100644
--- a/nixos/modules/installer/tools/nixos-rebuild.sh
+++ b/nixos/modules/installer/tools/nixos-rebuild.sh
@@ -26,7 +26,8 @@ while [ "$#" -gt 0 ]; do
       --help)
         showSyntax
         ;;
-      switch|boot|test|build|dry-run|build-vm|build-vm-with-bootloader)
+      switch|boot|test|build|dry-build|dry-run|dry-activate|build-vm|build-vm-with-bootloader)
+        if [ "$i" = dry-run ]; then i=dry-build; fi
         action="$i"
         ;;
       --install-grub)
@@ -137,7 +138,7 @@ fi
 
 # First build Nix, since NixOS may require a newer version than the
 # current one.
-if [ -n "$rollback" -o "$action" = dry-run ]; then
+if [ -n "$rollback" -o "$action" = dry-build ]; then
     buildNix=
 fi
 
@@ -180,7 +181,7 @@ if [ -n "$canRun" ]; then
 fi
 
 
-if [ "$action" = dry-run ]; then
+if [ "$action" = dry-build ]; then
     extraBuildFlags+=(--dry-run)
 fi
 
@@ -193,7 +194,7 @@ if [ -z "$rollback" ]; then
     if [ "$action" = switch -o "$action" = boot ]; then
         nix-env "${extraBuildFlags[@]}" -p "$profile" -f '<nixpkgs/nixos>' --set -A system
         pathToConfig="$profile"
-    elif [ "$action" = test -o "$action" = build -o "$action" = dry-run ]; then
+    elif [ "$action" = test -o "$action" = build -o "$action" = dry-build -o "$action" = dry-activate ]; then
         nix-build '<nixpkgs/nixos>' -A system -k "${extraBuildFlags[@]}" > /dev/null
         pathToConfig=./result
     elif [ "$action" = build-vm ]; then
@@ -224,7 +225,7 @@ fi
 
 # If we're not just building, then make the new configuration the boot
 # default and/or activate it now.
-if [ "$action" = switch -o "$action" = boot -o "$action" = test ]; then
+if [ "$action" = switch -o "$action" = boot -o "$action" = test -o "$action" = dry-activate ]; then
     if ! $pathToConfig/bin/switch-to-configuration "$action"; then
         echo "warning: error(s) occured while switching to the new configuration" >&2
         exit 1