To mount the /usr/ports directory inside a jail on a FreeBSD system, you will need to do the following:
Make sure that the jail is running and has access to the file system where the /usr/ports directory is located. This typically means that the jail needs to be created on the same file system as the /usr/ports directory.
Create a mount point for the /usr/ports directory inside the jail. This can be done by creating a new directory in the jail, such as /mnt/ports.
Use the mount command to mount the /usr/ports directory at the mount point inside the jail. The mount command needs to be run from within the jail, either by logging in to the jail or using a utility such as jexec.
For example, to mount the /usr/ports directory at the /mnt/ports mount point inside the jail, you can run the following command from within the jail:
# mount /usr/ports /mnt/ports
This will mount the /usr/ports directory at the /mnt/ports mount point inside the jail.
To unmount the /usr/ports directory, you can use the umount command:
# umount /mnt/ports
Note that you will need to have the necessary permissions to mount and unmount file systems on the system.
For more information about mounting file systems inside a jail on a FreeBSD system, you can refer to the FreeBSD documentation and the mount and umount man pages by running man mount and man umount on the command line.