mkdir: cannot create directory ‘/var/ftp/userdir’: No such file or directory

This error message indicates that the "mkdir" command is attempting to create a directory named "userdir" within the "/var/ftp" directory, but the "/var/ftp" directory does not exist.

To resolve this issue, you need to create the "/var/ftp" directory first, then create the "userdir" directory within it. You can do this by running the following commands:

sudo mkdir /var/ftp
sudo mkdir /var/ftp/userdir

The "sudo" command is used to run these commands with administrative privileges, which may be necessary depending on your system configuration.