This tutorial shows you how to fix 504 gateway Timeout on Nginx

來源： How To Fix 504 Gateway Time-out on Nginx – idroot

Linux服务器通常需要远程登录访问，尤其是当服务器或VPS还允许root直接登录时，应该为SSH登录成功配置一个自动的email提醒。

sendmail直接发送的话很可能会发送到垃圾邮箱里，需要把地址加入到白名单。

把下面的admin@hackhp.com更改为你要接收登录通知的电子邮件地址。

CentOS

vim ~/.bash_profile

IP="$(echo $SSH_CONNECTION | cut -d " " -f 1)"
HOSTNAME=$(hostname)
NOW=$(date +"%e %b %Y, %a %r")

echo 'Someone from '$IP' logged into '$HOSTNAME' on '$NOW'.' | mail -s 'SSH Login Notification' admin@hackhp.com

Ubuntu/Debian

vim ~/.bashrc

IP="$(echo $SSH_CONNECTION | cut -d " " -f 1)"
HOSTNAME=$(hostname)
NOW=$(date +"%e %b %Y, %a %r")

echo 'Someone from '$IP' logged into '$HOSTNAME' on '$NOW'.' | mail -s 'SSH Login Notification' admin@hackhp.com

如果不想接收到邮箱，只想重定向到一个文件的话。

IP="$(echo $SSH_CONNECTION | cut -d " " -f 1)"
HOSTNAME=$(hostname)
NOW=$(date +"%e %b %Y, %a %r")
echo 'Someone from '$IP' logged into '$HOSTNAME' on '$NOW'.' >>/root/login.txt

Step One—Install Deny Hosts

We need to use a repository to install Deny Hosts on CentOS.

sudo rpm -Uvh http://mirror.metrocast.net/fedora/epel/6/i386/epel-release-6-8.noarch.rpm

sudo yum install denyhosts

Once the program has finished downloading to the VPS, denyhosts is installed and configured.

yum install denyhosts

http://blogger.liaohaha.tw/2012/02/denyhosts.html