Flash Nexus 5 Manually

• fastboot erase boot
• fastboot erase cache
• fastboot erase recovery
• fastboot erase system
• fastboot flash bootloader "name-of-bootloader.img"
• fastboot reboot-bootloader
• fastboot flash radio "name-of-radio.img" (if present)
• fastboot reboot-bootloader
• fastboot flash system system.img
• fastboot flash boot boot.img
• fastboot flash recovery recovery.img
• fastboot flash cache cache.img
• fastboot flash vendor vendor.img (Nexus 9 only)
• fastboot erase userdata
• fastboot flash userdata userdata.img
• fastboot reboot

Source : http://www.howtogeek.com/176284/how-to-upgrade-your-nexus-device-without-waiting-by-flashing-a-factory-image/