I'm studying linux server book. I'm now seeing telnet.
they say after install telnet, I should modify telnet configure in /etc/xinetd.d/telnet
but there is no telnet file. but install is well finished.
Fedora 23 is based on Systemd. The Fedora 23 telnet-server
(that's what you installed) uses sytemd service units to manage the telnetd service. To enable it, run systemctl enable telnetd.socket and to start it, systemctl start telnetd.socket
. Use this /usr/lib/systemd/system/telnet.socket
instead for checking configuration.