How to allow install of non app store or identified developers on MacOS Sierra

Question

I'm getting this error trying to install software on MacOS Sierra (10.12.5):

Your security preferences allow installation of only apps from the App Store and identified developers.

I'd like to change the settings so that these types of installations are allowed. Similar to what is shown here:

http://www.synergy.com/wordpress_650164087/faqs/if-you-get-the-following-error-trying-to-install-kg-under-os-10-8-your-security-preferences-allow-installation-of-only-apps-from-the-mac-app-store-and-identified-developers/

However, my system doesn't seem to have the Anywhere option (screen shot below). This option is also not available if the Advanced button is selected.

Answer 1

From: How to Allow Apps from Anywhere in macOS Sierra Gatekeeper

1. Quit out of System Preferences

2. Open the Terminal app from the /Applications/Utilities/ folder and then enter the following command syntax:
   

   sudo spctl --master-disable
   

3. Hit return and authenticate with an admin password

4. Relaunch System Preferences and go to “Security & Privacy” and the “General” tab

5. You will now see the “Anywhere” option under ‘Allow apps downloaded from:’ Gatekeeper options

Answer 2

Just right-click (or ^ ctrl click) the pkg file in question and choose Open. This will let you open the file no matter where it came from. Note that this is different from double-clicking.

You can do this with any application downloaded from the Internet, and macOS will remember that application next time you run it.

From a security standpoint, I prefer doing this over disabling the safeguard systemwide.

Answer 3

To do this without needing admin privileges and without disabling security features:

• Open up terminal
• Type xattr -c
• Drag (from finder) the file you wish to open into the terminal window
• Run the command by pressing Enter

xattr -c removes the metadata of a file or folder. This removes the developer, date of download and a few other things. It does not effect the contents of the app.

Answer 4

As of macOS High Sierra 10.13.4, right-clicking (or ^ ctrl clicking) .app packages, which are not registered with Apple by an identified developer, and choosing Open won't work, so the only option left is to enable the Anywhere option under Security and Privacy in System Preferences (at least temporarily).

From How to open apps from unidentified developers on macOS Sierra:

1. Close System Preferences on your Mac.
2. Open Terminal.

3. Type the following command:

   sudo spctl --master-disable

4. Hit enter on your keyboard.

5. Enter your administrator password.
6. Hit enter on your keyboard.

This will restore the Anywhere setting and select it by default. To verify you can open System Preferences and select Security & Privacy.

To return to the default and more secure GateKeeper settings, follow the same steps, changing the command to sudo spctl --master-enable