问题：
[hadoop@hadoop001 conf]$ nc -lk 9999
-bash: nc: command not found
从提示信息中我们可以知道，是由于nc命令无法被找到
没有配置nc的命令
解决：
[root@hadoop001 ~]# yum install -y nc
[root@hadoop001 ~]# yum install -y nc
Loaded plugins: fastestmirror
base | 3.6 kB 00:00:00
epel | 4.7 kB 00:00:00
extras | 3.4 kB 00:00:00
updates | 3.4 kB 00:00:00
(1/6): extras/7/x86_64/primary_db | 156 kB 00:00:00
(2/6): base/7/x86_64/group_gz | 166 kB 00:00:00
(3/6): epel/x86_64/updateinfo | 953 kB 00:00:00
(4/6): updates/7/x86_64/primary_db | 1.3 MB 00:00:00
(5/6): epel/x86_64/primary_db | 6.6 MB 00:00:01
(6/6): base/7/x86_64/primary_db | 6.0 MB 00:00:01
Determining fastest mirrors
Resolving Dependencies
--> Running transaction check
---> Package nmap-ncat.x86_64 2:6.40-16.el7 will be installed
--> Finished Dependency Resolution
Dependencies Resolved
====================================================================================
Package Arch Version Repository Size
====================================================================================
Installing:
nmap-ncat x86_64 2:6.40-16.el7 base 206 k
Transaction Summary
====================================================================================
Install 1 Package
Total download size: 206 k
Installed size: 423 k
Downloading packages:
nmap-ncat-6.40-16.el7.x86_64.rpm | 206 kB 00:00:00
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
Installing : 2:nmap-ncat-6.40-16.el7.x86_64 1/1
Verifying : 2:nmap-ncat-6.40-16.el7.x86_64 1/1
Installed:
nmap-ncat.x86_64 2:6.40-16.el7
Complete!
解决
[hadoop@hadoop001 conf]$ nc -lk 9999
a,a,a,