Unable to create files in mac root directory

The reason is that
mac os has introduced the System Integrity Protection (SIP) mechanism and cannot create new files in the / and /usr directories.

Solution 1:
Open the terminal and enter

csrutil status

Displaying enabled indicates that SIP is enabled, and you need to disable SIP next;

Restart your mac and hold down command+R to enter recovery mode;

Click the fourth column of utility tools in the upper left corner of the screen: Terminal, open the terminal, enter csrutil disable, and restart;

After restarting, you will find that you still cannot create new files and will prompt Read-only file system. At this time, you need to remount the root directory:

sudo mount -uw

After remounting, you can create a new folder, but this mount will become invalid after the computer is restarted, that is, it will revert to the Read-only file system after the restart;

To re-enable SIP, you need to re-enter recovery mode, enter csrutil enable and then restart.

Solution 2:

Create a new /etc/synthetic.conf file:

sudo vim /etc/synthetic.conf

Add directory mapping to the file. Each line is equivalent to creating a soft link. It contains three columns. The first column represents the directory name under the root directory/, and the second column is a tab key \t (cannot be a space). The third column is its own directory:

data	/Users/my/data

The above configuration is equivalent to ln -s /Users/my/data /data

Restart your mac and you will see an additional /data directory in the root directory.