A package may be declared absent, and an uninstalled front end is retired for good (hq ADR 0175)

absent: true on a package has the host remove it through the machine's own
package manager when it is installed and leave alone a machine that never had
it; read back either way. Undeclaring a package still removes nothing. A
found firewall whose command is gone is recorded as removed, said once, and
asked nothing of.

internal/system/alpine.go

@@ -46,6 +46,11 @@ func (a alpine) PackageInstalled(ctx context.Context, run Runner, name string) (
 	return strings.TrimSpace(out) != "", nil
 }
 
+func (alpine) RemovePackage(ctx context.Context, run Runner, name string) error {
+	_, err := run(ctx, "apk", "del", name)
+	return err
+}
+
 func (alpine) InstallPackage(ctx context.Context, run Runner, name string) error {
 	_, err := run(ctx, "apk", "add", "--no-cache", name)
 	return err

internal/system/android.go

@@ -65,6 +65,10 @@ func (a android) InstallPackage(context.Context, Runner, string) error {
 	return fmt.Errorf("%w: package", ErrUnsupported)
 }
 
+func (a android) RemovePackage(context.Context, Runner, string) error {
+	return fmt.Errorf("%w: package", ErrUnsupported)
+}
+
 func (a android) ServiceState(context.Context, Runner, string) (string, error) {
 	return "", fmt.Errorf("%w: service (init is not reachable without root)", ErrUnsupported)
 }

internal/system/arch.go

@@ -39,6 +39,14 @@ func (a arch) PackageInstalled(ctx context.Context, run Runner, name string) (bo
 	return true, nil
 }
 
+// RemovePackage removes one package and nothing it depends on: `-R`, not `-Rs`, because what else
+// relied on a dependency is not this declaration's to know. pacman keeps a configuration file the
+// operator changed as `.pacsave`, which is what "never flushed" comes to once the front end is gone.
+func (arch) RemovePackage(ctx context.Context, run Runner, name string) error {
+	_, err := run(ctx, "pacman", "-R", "--noconfirm", name)
+	return err
+}
+
 func (arch) InstallPackage(ctx context.Context, run Runner, name string) error {
 	out, err := run(ctx, "pacman", "-S", "--noconfirm", "--needed", name)
 	if err == nil {

internal/system/system.go

@@ -51,6 +51,9 @@ type System interface {
 
 	PackageInstalled(ctx context.Context, run Runner, name string) (bool, error)
 	InstallPackage(ctx context.Context, run Runner, name string) error
+	// RemovePackage uninstalls one package, leaving its dependencies and anything the operator
+	// changed in its configuration where the package manager leaves them (novox/hq ADR 0175).
+	RemovePackage(ctx context.Context, run Runner, name string) error
 
 	// ServiceState is "running" or "stopped". A unit that does not exist is an error, never
 	// "stopped" — reporting absence as satisfaction is the fault this host exists to prevent.