我现在使用的系统是ubuntu12.10，默认使用network manager作为网络管理器，就在屏幕右上方，这里他的VPN是不能配置的，需要安装一个插件。

sudo apt-get install network-manager-gnome network-manager-pptp

sudo apt-get install network-manager-openvpn // 安装OpenVPN协议管理器

sudo NetworkManager restart // 重启
接下来需要将openvpn的配置文件复制到/etc/openvpn目录下。
sudo cp ca.crt client.crt client.key client.ovpn /etc/openvpn/
接下来就是启动openvpn了。拨openvpn的方法有两种：一种是通过network manager创建一个vpn连接（这个比较麻烦，不在这里讲解，大家可以自己去尝试）;另一种方法是通过命令行来拨openvpn。

启动命令如下：

cd /etc/openvpn && sudo openvpn –config /etc/openvpn/openvpn_client.ovpn
 

注意1：必须以root权限执行。如果不以root权限执行，报错如下

netcat@netcat:/etc/openvpn$ openvpn –config /etc/openvpn/openvpn_client.ovpn

Fri Feb 22 13:38:29 2013 OpenVPN 2.2.1 i686-linux-gnu [SSL] [LZO2] [EPOLL] [PKCS11] [eurephia] [MH] [PF_INET6] [IPv6 payload 20110424-2 (2.2RC2)] built on Oct 8 2012

Fri Feb 22 13:38:29 2013 WARNING: No server certificate verification method has been enabled. See http://openvpn.net/howto.html#mitm for more info.

Fri Feb 22 13:38:29 2013 NOTE: OpenVPN 2.1 requires ‘–script-security 2’ or higher to call user-defined scripts or executables

Fri Feb 22 13:38:29 2013 Cannot load private key file houwenhui.key: error:0200100D:system library:fopen:Permission denied: error:20074002:BIO routines:FILE_CTRL:system lib: error:140B0002:SSL routines:SSL_CTX_use_PrivateKey_file:system lib

Fri Feb 22 13:38:29 2013 Error: private key password verification failed

Fri Feb 22 13:38:29 2013 Exiting
注意2：必须在/etc/openvpn目录下执行，否则报错如下：
netcat@netcat:~$ sudo openvpn –config /etc/openvpn/openvpn_client.ovpn

Fri Feb 22 13:39:04 2013 OpenVPN 2.2.1 i686-linux-gnu [SSL] [LZO2] [EPOLL] [PKCS11] [eurephia] [MH] [PF_INET6] [IPv6 payload 20110424-2 (2.2RC2)] built on Oct 8 2012

Fri Feb 22 13:39:04 2013 WARNING: No server certificate verification method has been enabled. See http://openvpn.net/howto.html#mitm for more info.

Fri Feb 22 13:39:04 2013 NOTE: OpenVPN 2.1 requires ‘–script-security 2’ or higher to call user-defined scripts or executables

Fri Feb 22 13:39:04 2013 Cannot load certificate file houwenhui.crt: error:02001002:system library:fopen:No such file or directory: error:20074002:BIO routines:FILE_CTRL:system lib: error:140AD002:SSL routines:SSL_CTX_use_certificate_file:system lib

Fri Feb 22 13:39:04 2013 Exiting