https://wiki.archlinux.org/index.php/Touchpad_Synaptics
wiki很好，建議閱讀。
可以用synclient命令來配置屬性，
synclient TapButton1 = 1
一開始我的觸摸板觸碰沒有點擊的效果，必須要按鍵，現在在這裏設置就行了
TapButton1 = 1
TapButton2 = 3
TapButton3 = 2
如此一指觸碰即左鍵單擊，兩指觸碰也就是右擊，三指是按下中間滾輪，很方便
這在終端複製時很方便。
CircularScrolling這一選項可以順時針和逆時針上下翻頁，
把他的值改爲1就可以了，circscrolltrigger默認爲零，表示在任何邊緣開始轉圈都可以。
感到滿意了，就把配置寫入配置文件中，具體的參見wiki
如果在GDM登錄窗口無法使用觸摸板按鍵，按照以下方法可解決：
You have to export $(dbus-launch) and set the gsettings backend (tested on archlinux with gdm 3.18.2):
switch to a VT (e.g. Ctrl+Alt+F3), login as root and run:
su - gdm -s /bin/sh
to switch user to gdm.
then run:
export $(dbus-launch)
and:
GSETTINGS_BACKEND=dconf gsettings set org.gnome.desktop.peripherals.touchpad tap-to-click true
run exit or hit Ctrl+D to return to root account.
restart the display manager:
systemctl restart gdm
Reverting is pretty much the same, just change true to false @ step 2.
http://unix.stackexchange.com/questions/266586/gdm-how-to-enable-touchpad-tap-to-click