CentOS设置网络访问代理

Configuring Web Proxy on CentOS
If your internet connection is behind a web proxy, you need to configure the following on your CentOS server:

System-wide proxy settings - add the following lines to your /etc/environment file:
# vi /etc/environment
http_proxy="http://<proxy_host>:<proxy_port>/"
https_proxy="https://<proxy_host>:<proxy_port>/"
ftp_proxy="ftp://<proxy_host>:<proxy_port>/"
no_proxy=".mylan.local,.domain1.com,host1,host2"

To apply these settings without restarting the machine run the following commands on the bash shell:
export http_proxy="http://<proxy_host>:<proxy_port>/"
export https_proxy="https://<proxy_host>:<proxy_port>/"
export ftp_proxy="ftp://<proxy_host>:<proxy_port>/"
export no_proxy=".mylan.local,.domain1.com,host1,host2"

You also need to configure yum:
# vi /etc/yum.conf
proxy=http://<proxy_host>:<proxy_port>
Save and close the file, then clear the cache used by yum with the following command:
#yum clean all

You also need to configure wget:
# vi /etc/wgetrc    or    vi ~/.wgetrc
https_proxy = http://<proxy_host>:<proxy_port>
http_proxy = http://<proxy_host>:<proxy_port>
ftp_proxy = http://<proxy_host>:<proxy_port>
proxy_user=username
proxy_password=password

You also need to configure curl:
You can make a alias in your ~/.bash_profile file :
alias curl="curl -x <proxy_host>:<proxy_port>"
Another solution is to use (maybe the better solution) the ~/.curlrc file (create it if it does not exist) :
proxy = <proxy_host>:<proxy_port>