Hello, I check my website and see today was downtime 2hour, How i can check why this happend ? I use CentOS 6.6 (64bits) Thanks.
Check your server logs. Was there a gap in traffic to your websites during the 2 hours? Was there maintenance going on, a software rebuild? Was the server actually down or was there a problem somewhere along the network from your computer to your server? A lot of people mistakenly think their server is down when the fact is it is up and serving visitors, there is just a problem between your ISP and your server somewhere along the line. I see it all the time.
You should check the apache domlogs, at /usr/local/apache/domlogs/domain.com or just in your domlogs folder in apache installation directory if not that one. You can also check the error_log at /usr/local/apache/logs/error_log and the server message log at /var/log/messages for indicators as to what the issue was.