With fail2ban, what is a 'jail'?

What is the path to the global Postfix configuration file? (Specify the full name of the file, including path.)

In order to export /usr and /bin via NFSv4, /exports was created and contains working bind mounts to /usr and /bin.
The following lines are added to /etc/exports on the NFC server:

After running mount-tnfsv4 server://mnt of an NFC-Client, it is observed that /mnt contains the content of the server's /usr directory instead of the content of the NFSv4 foot folder.
Which option in /etc/exports has to be changed or removed in order to make the NFSv4 root folder appear when mounting the highest level of the server?
(Specify ONLY the option name without any values or parameters.)

Which option in named.conf specifies which host are permitted to ask for domain name information from the server?

Which of the following commands can be used to connect and interact with remote TCP network services?
(Choose two.)