Why and how to fix Ubuntu: apt get :Package has no installation

When I type this command at the terminal, it says telnetd: apt-get :Package has no installation

sudo apt-get install xinetd telnetd 

At the beginning, I thought there was no package. Later, I checked the data and found that there was this software. Therefore, I didn't know the following operation was needed to solve the above problems until I checked the data.

# apt-get update 
# apt-get upgrade 
# apt-get install <packagename> 

This will allow you to use apt-get as normal.

Next, follow the steps in the previous reprinted article to configure the telent server:

//www.ofstack.com/article/98670.htm

Note: in/usr sbin/in telnetd must want to have this file, because this is install telnetd needs a service, without it, during a visit to the server remote telnetd will be 23 port access denied.