How to allow USB to Serial adapters in OSX “El Capitan”

I use a Mac as my daily laptop.  I sometimes have to console into really old Cisco devices.  If you find that after updating to OSX El Capitan, your USB to Serial adapters aren’t showing up anymore, here is what you’ll need to do.


WARNING: This will disable the new Rootless protection.


OSX 10.11 has a new feature called “System Integrity Protection” that blocks any kind of third party driver from being used.  This is also referred to as “Rootless”.  This process will turn that off and allow you to run processes that can modify system files.

  1. Install your USB Serial adapter drivers if you haven’t already done so.
  2. Open a terminal and type sudo nvram boot-args="kext-dev-mode=1 rootless=0"
  3. Reboot.
  4. Open terminal with USB adapter attached and cd to /dev
  5. type ls and your adapter should show up like tty.usbserial.

36 Responses

  1. James Morris says:

    boot mac into recovery mode (command+r). hold it down until you see the mouse cursor
    utilities, terminal
    csrutil status
    probably says enabled
    csrutil disable

  2. Chris K says:

    If you don’t want to disable system integrity protection, and you’re using your adapter with a terminal program to console into devices, I developed a terminal app that doesn’t require you to install drivers and works perfectly with El Capitan. It’s called Serial, available on the Mac App Store.

    I also know the people at mac-usb-serial dot com (no affiliation) are working on a signed version of their driver for the PL2303 that works with 10.11. It’s commercial too, but seems to work well and will allow you to use your device with any program on the Mac. (My app, Serial, doesn’t make the port available to other applications).

    Unfortunately the “official” Prolific driver from the manufacturer still remains unsigned, and won’t work with Yosemite or El Capitan without disabling security features. You could try putting some pressure on them to update their driver as well…

    Hope this helps, and hope you don’t mind the shameless plug for my app.

  3. Michael Newton says:

    This is very poor advice. There are going to be lots of folks randomly plugging commands into their Macs to get something or other working, and this should not be one of those commands.

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  6. Ntwk says:

    I updated my prolific drivers for MAC (El Capitan) no joy. However, I will note the USB driver reflects version 3 instead of Version 4 per the prolific PDF.
    Came to this website.
    I ran the command:
    sudo nvram boot-args=”kext-dev-mode=1 rootless=0″
    I disabled csrutil in recovery mode and rebooted.

    Still does not work.
    I bought the app mentioned above and no joy.

    I have confirmed the settings and I know my Pluggable USB to Serial is good.

    I am not sure where to go next.

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