You can also upgrade the system by turning off sip. The system interrupted the download during the patch download process, that is, the completed patch package was not downloaded. The specific reason is that Apple has fully enabled a system integrity protection technology called System Integrity Protection (SIP) in 10.11. As a result, many unsigned third-party kexts and modified original kexts cannot be loaded and used. Even if most system files are It cannot be modified directly under the root user. Therefore, you need to temporarily turn off this SIP function before you can continue to complete the system update.