打开 /etc/apt/sources.list 添加下面两行

Ubuntu ：
deb http://nginx.org/packages/ubuntu/ lucid nginx
deb-src http://nginx.org/packages/ubuntu/ lucid nginx

debian：
deb http://nginx.org/packages/debian/ squeeze nginx
deb-src http://nginx.org/packages/debian/ squeeze nginx

更新包、安装nginx
apt-get update
apt-get install nginx

提示：

Configuration file `/etc/nginx/nginx.conf'
==> Modified (by you or by a script) since installation.
==> Package distributor has shipped an updated version.
What would you like to do about it ? Your options are:
Y or I : install the package maintainer's version
N or O : keep your currently-installed version
D : show the differences between the versions
Z : background this process to examine the situation
The default action is to keep your current version.
*** nginx.conf (Y/I/N/O/D/Z) [default=N] ?

这时输入N，保留之前的nginx.conf配置。

完成安装后，重启nginx
service nginx restart

完成更新，可以输入以下命令查看当前版本。
nginx -v