Archives for February 2017

A TCP/IP network connection may be either blocked, dropped, open, or filtered. These actions are generally controlled by the IPtables firewall the system uses and is independent of any process or program that may be listening on a network port. Beyond the firewall, a program or process (a server or daemon) may be listening on a port or not listening. This can be checked using the netstat or ss programs. Checking to see if a port is open, blocked, dropped, or filtered at the firewall is not … [Read more...] about CentOS / RHEL : How to find if a network port is open or not?

There are two ways to add another IP address to an interface. The old way creates a new virtual interface named in the style of ethX:Y where X and Y are numbers, for instance, eth0:1. Each interface has one IP address. It appears in ifconfig output as an ordinary interface and in ip output with a label attached. The new way adds a secondary address to the main interface. So, instead of having one interface per IP address, it is possible to add many addresses to the real interface. However, … [Read more...] about CentOS / RHEL 6 : How to add/remove additional IP addresses to a network interface

Question: How to prevent disabled repositories from being downloaded into the yum cache Answer: Yum does not fetch content from disabled repositories, but the yum cache may still hold a record of these repositories. The command "yum clean all" does not try to remove content from disabled repositories. So, to entirely get rid of them, use # rm -rf /var/cache/yum/* … [Read more...] about CentOS / RHEL : How to prevent disabled repositories from being downloaded into the yum cache