这个问题是简单的没有下载ping

root@ubuntu:/# ping www.baidu.com
bash: ping: command not found

下载就好了

root@ubuntu:/#  apt-get install inetutils-ping
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following NEW packages will be installed:
  inetutils-ping
0 upgraded, 1 newly installed, 0 to remove and 31 not upgraded.
Need to get 56.9 kB of archives.
After this operation, 338 kB of additional disk space will be used.
Get:1 http://archive.ubuntu.com/ubuntu xenial/universe amd64 inetutils-ping amd64 2:1.9.4-1build1 [56.9 kB]
Fetched 56.9 kB in 1s (35.7 kB/s)         
debconf: unable to initialize frontend: Dialog
debconf: (No usable dialog-like program is installed, so the dialog based frontend cannot be used. at /usr/share/perl5/Debconf/FrontEnd/Dialog.pm line 76, <> line 1.)
debconf: falling back to frontend: Readline
Selecting previously unselected package inetutils-ping.
(Reading database ... 24501 files and directories currently installed.)
Preparing to unpack .../inetutils-ping_2%3a1.9.4-1build1_amd64.deb ...
Unpacking inetutils-ping (2:1.9.4-1build1) ...
Setting up inetutils-ping (2:1.9.4-1build1) ...