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macOS Big Sur

When executing sudo mkdir xxx in the root directory of macOS Monterey, the error message Read-only file system is returned.

For security and protection purposes, Apple has restricted the ability to create files in the root directory starting from macOS Big Sur. Even if you use sudo with root privileges, you cannot create files directly in the root directory. However, Apple has provided a workaround solution using Firmlinks, a link mechanism similar to Unix symbolic links, that can satisfy specific user requirements without compromising the system. Many online solutions require users to restart the computer and enter recovery mode, which is complicated.