ubnutu的任务栏都是在左侧：
zhang@zhang-virtual-machine:~$ gsettings set com.canonical.Unity.Launcher launcher-position Bottom #底部（苹果风格）
zhang@zhang-virtual-machine:~$ gsettings set com.canonical.Unity.Launcher launcher-position Left #左侧（默认）
zhang@zhang-virtual-machine:~$ gsettings set com.canonical.Unity.Launcher launcher-position Right #右侧
zhang@zhang-virtual-machine:~$ gsettings set com.canonical.Unity.Launcher launcher-position Top #顶部
