diff --git a/Install-preparations.md b/Install-preparations.md
index e506870..5fba146 100644
--- a/Install-preparations.md
+++ b/Install-preparations.md
@@ -1,17 +1,16 @@
 # 1. Ubuntu:
 
+The default `netcat` tool doesn't support `-4` , `-6` and local address, So, please install `netcat-openbsd` to support all the options.
+
 ```
 apt-get install openssl cron  netcat-openbsd  curl
 ```
 
-Or install `netcat`.
-```
-apt-get install netcat
-```
-
 
 # 2. CentOS
 
+The default `nc` tool doesn't support `-4` , `-6` and local address, So, please install `netcat-openbsd` to support all the options.
+
 ```
 yum -q -y install  openssl  crontabs  netcat-openbsd curl
 ```
@@ -21,10 +20,6 @@ For centos 5:
 yum -q -y install openssl vixie-cron netcat-openbsd curl
 ```
 
-Or install `nc`
-```
-yum -q -y install nc
-```
 
 # 3. alpine