安装telnet出错

安装telnet出错
#sudo apt-get install telnet-server

sudo: /etc/sudoers.d is world writable
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Package telnet-server is a virtual package provided by:
  heimdal-servers 1.6~git20131207+dfsg-1ubuntu1.2
  telnetd-ssl 0.17.24+0.1-24
  telnetd 0.17-36build2
  inetutils-telnetd 2:1.9.2-1
You should explicitly select one to install.

E: Package 'telnet-server' has no installation candidate

解决方法如下：

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