diff --git a/README.md b/README.md
index eca6ef1..4601fe6 100644
--- a/README.md
+++ b/README.md
@@ -21,6 +21,8 @@ systemctl may be used to introspect and control the state of the "systemd" syste
 - [ ] `systemctl is-enabled`
 - [ ] `systemctl daemon-reload`
 - [ ] `systemctl show`
+- [ ] `systemctl mask`
+- [ ] `systemctl unmask`
 
 ## TODO
 
diff --git a/errors.go b/errors.go
new file mode 100644
index 0000000..c5313c7
--- /dev/null
+++ b/errors.go
@@ -0,0 +1,14 @@
+package systemctl
+
+import (
+	"errors"
+)
+
+var (
+	// ErrSystemctlNotInstalled means that upon trying to manually locate systemctl in the user's path,
+	// it was not found. If this error occurs, the library isn't entirely useful.
+	ErrNotInstalled = errors.New("systemd binary was not found")
+
+	// ErrExecTimeout means that the provided context was done before the command finished execution.
+	ErrExecTimeout = errors.New("command timed out")
+)
diff --git a/systemctl.go b/systemctl.go
index ec94ff6..4d54196 100644
--- a/systemctl.go
+++ b/systemctl.go
@@ -49,6 +49,17 @@ func IsEnabled(unit string) (bool, error) {
 func DaemonReload(unit string) error {
 	return nil
 }
+
+//TODO
 func Show(unit string, property string) (string, error) {
 	return "", nil
 }
+
+//TODO
+func Mask(unit string) error {
+	return nil
+}
+
+func Unmask(unit string) error {
+	return nil
+}