kali@kali:~$ sudo apt-get install xterm<br>
[sudo] password for kali: <br>
Reading package lists... Done<br>
Building dependency tree <br>
Reading state information... Done<br>
Package xterm is not available, but is referred to by another package.<br>
This may mean that the package is missing, has been obsoleted, or
is only available from another source<br>
<br>
E: Package 'xterm' has no installation candidate<br>
首先执行sudo apt-get update，然后尝试sudo apt-get install xterm。