netstat HowTo - Linux / Unix Q & A from nixCraft

How to check if port is in use on Linux or Unix

last updated August 11, 2019 in CentOS, Debian / Ubuntu, FreeBSD, Linux, RedHat and Friends, Suse, UNIX

How do I determine if a port is in use under Linux or Unix-like system? How can I verify which ports are listening on Linux server? How do I check if port is in use on Linux operating system using the CLI?

Linux: Check Network Connection Command

last updated January 10, 2011 in Linux, Networking

How do I check network connections under Linux using command line options?

ping command: TTL Expired In Transit Error and Solution

last updated October 27, 2010 in BASH Shell, Networking

When I try to ping other UNIX / Linux / BSD or MS-Windows servers in our network I get the following message:

TTL Expired In Transit

How do I fix this problem?

CentOS / Redhat Linux: Install OpenNTPD To Synchronize The Local Clock

last updated November 22, 2016 in CentOS, Fedora Linux, Linux, Package Management, RedHat and Friends

OpenNTPD is a Unix system daemon implementing the Network Time Protocol to synchronize the local clock of a computer system with remote NTP servers. How do I install OpenNTPD under CentOS / RHEL / Fedora Linux instead of default NTPD client / server?