This is just a brief howto about installing and configuring NTPD (Network Time Protocol Daemon) on a Linux server which in this case is specifically NTPD. First we will install ntpd, then update the current time on the server, configure ntpd to restart on server boot, and then start ntpd.

1. Install NTPD: Run the below command to install ntpd via yum.

[root@server ~]# yum install ntp

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Tags: CentOS, chkconfig, grep, Linux, network time protocol, ntp, ntpd, ps, rdate, time

Follow the below directions to turn off selinux on a CentOS server. SeLinux can cause many issues and if your server is behind a properly configured firewall as well as the systems administrator only opens necessary ports that are configured properly your risks should be minimal.

1. Modify selinux Configuration:Modify the selinux config file by issuing the command below and changing the SELINUX option to disabled as shown below.

[root@server ~]#vi /etc/selinux/config

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Tags: CentOS, config, dmesg, grep, reboot, security, security enhanced linux, selinux

If you are in process of installing the NRPE daemon as an xinetd service for Nagios monitoring capabilities you may run across this error in /var/log/messages.

If you have started xinetd by typing the following:
shell# /etc/init.d/xinetd start

but you do not see the NRPE service listening by using netstat:
shell# netstat -an | grep 5666

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If you want to see the actual active lines from a configuration file in Linux you can exclude any lines with comments by issuing the below command.

shell# cat /etc/postfix/main.cf | grep -v “# *”

If you also want to exclude the blank lines from the file use this command.

shell# cat /etc/postfix/main.cf | grep -v “# *” | grep -v “^$”

Sometimes that does not catch every line so add one more grep to exclude the lines that does not catch like this.

shell#cat /etc/postfix/main.cf | grep -v “# *” | grep -v “^$” | grep -v “  “

I had created a script to run ask for a couple CLI arguements and then run httperf against a server. The goal was to load test a server for HTTP and for HTTPS. I added the –ssl switch but could not verify a couple things including if httperf had been compiled with SSL support or if the –ssl was working at all.

1. Was httperf installed with SSL support?
This is an easy one. If the –ssl option exists then your httperf was compiled with SSL support. I wasn’t sure since I installed httperf via YUM in CentOS. I also tested by compiling myself and both versions had SSL support. If you do compile yourself you can check compile-dir/config.status and see if SSL support compiled properly.
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