nixos/switch-to-configuration: Never unmount / or /nix (85c1c30f) · Commits · nix / nixpkgs

nixos/doc/manual/development/what-happens-during-a-system-switch.chapter.md

+3 −2

Original line number	Diff line number	Diff line
		@@ -21,8 +21,9 @@ If the action is `switch` or `test`, the currently running system is inspected
		and the actions to switch to the new system are calculated. This process takes
		two data sources into account: `/etc/fstab` and the current systemd status.
		Mounts and swaps are read from `/etc/fstab` and the corresponding actions are
		generated. If a new mount is added, for example, the proper `.mount` unit is
		marked to be started. The current systemd state is inspected, the difference
		generated. If the options of a mount are modified, for example, the proper `.mount`
		unit is reloaded (or restarted if anything else changed and it's neither the root
		mount or the nix store). The current systemd state is inspected, the difference
		between the current system and the desired configuration is calculated and
		actions are generated to get to this state. There are a lot of nuances that can
		be controlled by the units which are explained here.

nixos/modules/system/activation/switch-to-configuration.pl

+14 −4

Original line number	Diff line number	Diff line
		@@ -661,10 +661,20 @@ foreach my $mount_point (keys(%{$cur_fss})) {
		# Filesystem entry disappeared, so unmount it.
		$units_to_stop{$unit} = 1;
		} elsif ($cur->{fsType} ne $new->{fsType} \|\| $cur->{device} ne $new->{device}) {
		if ($mount_point eq '/' or $mount_point eq '/nix') {
		if ($cur->{options} ne $new->{options}) {
		# Mount options changed, so remount it.
		$units_to_reload{$unit} = 1;
		record_unit($reload_list_file, $unit);
		} else {
		# Don't unmount / or /nix if the device changed
		$units_to_skip{$unit} = 1;
		}
		} else {
		# Filesystem type or device changed, so unmount and mount it.
		$units_to_stop{$unit} = 1;
		$units_to_start{$unit} = 1;
		record_unit($start_list_file, $unit);
		$units_to_restart{$unit} = 1;
		record_unit($restart_list_file, $unit);
		}
		} elsif ($cur->{options} ne $new->{options}) {
		# Mount options changes, so remount it.
		$units_to_reload{$unit} = 1;

nixos/tests/switch-test.nix

+69 −0

Original line number	Diff line number	Diff line
		@@ -66,6 +66,25 @@ in {
		# Hello world!
		'';

		addedMount.configuration.virtualisation.fileSystems."/test" = {
		device = "tmpfs";
		fsType = "tmpfs";
		};

		addedMountOptsModified.configuration = {
		imports = [ addedMount.configuration ];
		virtualisation.fileSystems."/test".options = [ "x-test" ];
		};

		addedMountDevModified.configuration = {
		imports = [ addedMountOptsModified.configuration ];
		virtualisation.fileSystems."/test".device = lib.mkForce "ramfs";
		};

		storeMountModified.configuration = {
		virtualisation.fileSystems."/".device = lib.mkForce "auto";
		};

		simpleService.configuration = {
		systemd.services.test = {
		wantedBy = [ "multi-user.target" ];
		@@ -672,6 +691,56 @@ in {
		out = switch_to_specialisation("${machine}", "modifiedSystemConf")
		assert_contains(out, "starting the following units: dbus.service\n")

		with subtest("fstab mounts"):
		switch_to_specialisation("${machine}", "")
		# add a mountpoint
		out = switch_to_specialisation("${machine}", "addedMount")
		assert_lacks(out, "stopping the following units:")
		assert_lacks(out, "NOT restarting the following changed units:")
		assert_lacks(out, "\nrestarting the following units:")
		assert_lacks(out, "\nstarting the following units:")
		assert_contains(out, "the following new units were started: test.mount\n")
		# modify the mountpoint's options
		out = switch_to_specialisation("${machine}", "addedMountOptsModified")
		assert_lacks(out, "stopping the following units:")
		assert_lacks(out, "NOT restarting the following changed units:")
		assert_contains(out, "reloading the following units: test.mount\n")
		assert_lacks(out, "\nrestarting the following units:")
		assert_lacks(out, "\nstarting the following units:")
		assert_lacks(out, "the following new units were started:")
		# modify the device
		out = switch_to_specialisation("${machine}", "addedMountDevModified")
		assert_lacks(out, "stopping the following units:")
		assert_lacks(out, "NOT restarting the following changed units:")
		assert_lacks(out, "reloading the following units:")
		assert_contains(out, "\nrestarting the following units: test.mount\n")
		assert_lacks(out, "\nstarting the following units:")
		assert_lacks(out, "the following new units were started:")
		# modify both
		out = switch_to_specialisation("${machine}", "addedMount")
		assert_lacks(out, "stopping the following units:")
		assert_lacks(out, "NOT restarting the following changed units:")
		assert_lacks(out, "reloading the following units:")
		assert_contains(out, "\nrestarting the following units: test.mount\n")
		assert_lacks(out, "\nstarting the following units:")
		assert_lacks(out, "the following new units were started:")
		# remove the mount
		out = switch_to_specialisation("${machine}", "")
		assert_contains(out, "stopping the following units: test.mount\n")
		assert_lacks(out, "NOT restarting the following changed units:")
		assert_contains(out, "reloading the following units: dbus.service\n")
		assert_lacks(out, "\nrestarting the following units:")
		assert_lacks(out, "\nstarting the following units:")
		assert_lacks(out, "the following new units were started:")
		# change something about the / mount
		out = switch_to_specialisation("${machine}", "storeMountModified")
		assert_lacks(out, "stopping the following units:")
		assert_contains(out, "NOT restarting the following changed units: -.mount")
		assert_contains(out, "reloading the following units: dbus.service\n")
		assert_lacks(out, "\nrestarting the following units:")
		assert_lacks(out, "\nstarting the following units:")
		assert_lacks(out, "the following new units were started:")

		with subtest("services"):
		switch_to_specialisation("${machine}", "")
		# Nothing happens when nothing is changed