The hit is missed

Signed-off-by: YuPengZTE <yu.peng36@zte.com.cn>
(cherry picked from commit ced272984157e277523a942505435aa392913ac4)
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

docs/installation/linux/oracle.md

@@ -110,11 +110,11 @@ To create the `docker` group and add your user:
 
 2. Create the `docker` group.
 
-        sudo groupadd docker
+        $ sudo groupadd docker
 
 3. Add your user to `docker` group.
 
-        sudo usermod -aG docker username
+        $ sudo usermod -aG docker username
 
 4. Log out and log back in.