adb reboot bootloaderStep 3: Once the device boots into bootloader mode, enter the following command:
fastboot oem unlockYou will be prompted with some instructions on your Nexus, so follow those to proceed. Mac users- Step 1: Launch Terminal and type the following command to set up ADB and Fastboot automatically:
bash <(curl https://raw.githubusercontent.com/corbindavenport/nexus-tools/master/install.sh)>Step 2: Navigate to System Preferences > Keyboard – Shortcuts then click on Services. Find the New Terminal at Folder option and click to enable it. Step 3: Connect your Nexus device to your Mac via USB. Step 4: Extract the contents of the Lollipop factory image on the desktop inside a folder. Right-click on the folder, then float the mouse pointer on Services, click on New Terminal at Folder. Step 5: Enter the following command in the Terminal window to reboot the device into bootloader mode:
adb reboot bootloaderNow enter the following command to unlock the bootloader
fastboot oem unlockFollow any on-screen instructions on your Nexus to ultimately unlock your bootloader. Also See: Installing Lollipop on your Nexus Device!