今天是第二次安裝RAC，但是遇到了一個很奇怪的問題，這裏寫下來，防止以後發生類似的問題。
環境是：在Vmware Workstation 8上安裝兩個CentOS4.4 ，並配置好網絡，NTP，RAW，SSH以及參數等等。但是在檢查用戶等價時總是提示失敗，我也到網站上找了好幾篇文章來看，可以還是沒能解決，後來也按照ORACLE官方文檔來做了，但是還是失敗，鬱悶了半天，但是最後還是解決了，哎，其實這個真的不是問題啊，其他的文件都檢查了，就把這個個給遺漏了，做了大量無用的工作，最後還是回到了原點，哈哈。
錯誤提示如下：
[oracle@oel1 ~]$ /media/cdrecorder/cluvfy/runcluvfy.sh stage -pre crsinst -n oel1,oel2
Performing pre-checks for cluster services setup
Checking node reachability...
Node reachability check passed from node "oel1".
Checking user equivalence...
User equivalence check failed for user "oracle". #錯誤出現，正常情況下是 User equivalence check passed for user "oracle".
Check failed on nodes:
oel1
WARNING:
User equivalence is not set for nodes:
oel1
Verification will proceed with nodes:
oel2
Checking administrative privileges...
User existence check passed for "oracle".
Group existence check passed for "oinstall".
Membership check for user "oracle" in group "oinstall" [as Primary] passed.
Administrative privileges check passed.
Checking node connectivity...
Node connectivity check passed for subnet "128.192.0.0" with node(s) oel2.
Node connectivity check passed for subnet "10.10.10.0" with node(s) oel2.
Suitable interfaces for VIP on subnet "128.192.0.0":
oel2 eth0:128.192.0.2
Suitable interfaces for the private interconnect on subnet "10.10.10.0":
oel2 eth1:10.10.10.2
Node connectivity check passed.
Checking system requirements for 'crs'...
Total memory check passed.
Free disk space check passed.
Swap space check passed.
System architecture check passed.
Kernel version check passed.
Package existence check passed for "make-3.79".
Package existence check passed for "binutils-2.14".
Package existence check passed for "gcc-3.2".
Package existence check passed for "glibc-2.3.2-95.27".
Package existence check passed for "compat-db-4.0.14-5".
Package existence check failed for "compat-gcc-7.3-2.96.128".
Check failed on nodes:
oel2
Package existence check failed for "compat-gcc-c++-7.3-2.96.128".
Check failed on nodes:
oel2
Package existence check failed for "compat-libstdc++-7.3-2.96.128".
Check failed on nodes:
oel2
Package existence check failed for "compat-libstdc++-devel-7.3-2.96.128".
Check failed on nodes:
oel2
Package existence check passed for "openmotif-2.2.3".
Package existence check passed for "setarch-1.3-1".
Group existence check passed for "dba".
Group existence check passed for "oinstall".
User existence check passed for "nobody".
System requirement failed for 'crs'
Pre-check for cluster services setup was unsuccessful on all the nodes.
處理如下：
檢查了SSH沒問題
檢查了網絡沒問題，都可以正常通信
檢查了安裝包
但是問題依然存在，最近看了service ntpd status 都是stop的狀態，原來問題是出在這裏
把ntp服務重新啓動後，檢查通過，順利安裝crs軟件。
最後總結：
1。時間必須同步
2。public網卡的ip一定要記得設置網關，保證網關能ping通
3。保證ssh互信
4。需要的安裝包都裝上