I need an explanation of the meanings of "synaptic" and "synaptics". Linux Mint 19.1 on a HP Laptop. The laptop has a synaptics touchpad which I need to disable on bootup. A config file to do this goes in the directory /etc/X11/xorg.conf.d/ and the filename seems to be variously called synaptics.conf or 50-synaptics.conf or 70-synaptics.conf
Synaptics is a major manufacturer of laptop touchpads, and also the name of the widely-used Xorg touchpad driver that originated as a driver for Synaptics touchpads, but now covers other touchpad manufacturers' products too.
Synaptic without the s, however, is completely unrelated: it is a graphical APT package manager front-end for the GTK toolkit (i.e. native to the GNOME desktop).
Mint 19.1 is likely to use the newer
libinput X11 input driver instead of the dedicated synaptics touchpad driver used in previous versions; beginner6789's answer to this question or
man libinput may be helpful in configuring it.
Also, you can use the
xinput command without any parameters to list the X11 input devices, and then use
xinput --list-props <input device number of your touchpad> to view all the settings for it available through the current driver.
Before trying to manipulate the settings directly, note that your desktop environment may already be controlling some of the settings. For example, in KDE the "Synaptics Off" setting is controlled by the touchpad input device management of KDE System Settings: if you set the "Disable touchpad when typing" option, it will manipulate the "Synaptics Off" setting according to whether keystrokes have been recently detected or not.
I am using the synaptics driver for my Elan1300 clickpad with voidlinux. Mint could be different.
In my /usr/share/X11/xorg.conf.d/ is 70-synaptics.conf file I copied to /etc/X11/xorg.conf.d/70-synaptics.conf and edited with my settings. The /var/log/Xorg.0.log file shows if the xorg is using the synaptics driver. The synaptics driver has settings to disable the touchpad when running the Xserver.
The touchpad using the synaptics driver can be turned off in the config file:
Option "TouchpadOff" "true"
That should disable the touchpad as soon as the display manager begins. Some desktop managers can affect the way xorg works with the input devices so that would be different. After X begins then the touchpad can be turned off in the .xinitrc file or other startup file like this:
If the xf86-input-synaptics is not installed then the xf86-input-libinput might be activating the touchpad instead of the synaptics driver.
An excerpt from the Xorg.0.log file might have given better information and show how the touchpad is being setup or the xinput can also give some details.
The xorg.conf.d files could even be modified to ignore the touchpad in the evdev.conf, libinput.conf and synaptics.conf files and so prevent any touchpad driver from loading:
MatchIsTouchpad "on" Option "Ignore" "true"
So I suppose the synaptics package would not be needed just to disable all touchpads in the evdev and libinput drivers.
EDIT: This might not be enough because the Xserver could activate the touchpad as a simple mouse instead of a touchpad. Then a MatchProduct would be needed to completely Ignore the touchpad.
Unless a touchscreen driver is needed then blacklisting the hid_multitouch kernel module can also disable the touchpad. And building a custom kernel is also an option...
Try something like this to Ignore the touchpad no matter if Xorg tries to use the synaptics, libinput or mouse drivers:
Section "InputClass" Identifier "stop touchpad" MatchProduct "" Option "Ignore" "on" EndSection
Put the above into a config file in /etc/X11/xorg.conf.d say 99-stopit.conf and see what happens. Be sure to put the correct string into the MatchProduct maybe just "Synaptics" or other substring could work. Also there are alternatives like MatchPnPID, MatchVendor explained in the "xorg.conf" man page.