Tag Archives: linux

Change Runtime Settings for Linux Servers

I install RHEL on all my production machines and CentOS on all my test/development boxes. Installing the GUI is helpful for configuration, but you sure don’t want to run them that way all the time. So after everything is installed, configured and tested, I make the following change:

nano /etc/inittab

Change

id:5:initdefault:

To

id:3:initdefault:

Save the file and reboot the machine. When you want to launch a GUI, just run:

startx

Add a Virtual IP Address in Linux

nano /etc/sysconfig/network-scripts/ifcfg-eth0

Should look something like this


DEVICE=eth0
BOOTPROTO=static
BROADCAST=172.16.0.255
HWADDR=00:00:00:00:00:00
IPADDR=172.16.0.2
NETMASK=255.255.255.0
NETWORK=172.16.0.0
ONBOOT=yes

Duplicate that and open the new file

cp /etc/sysconfig/network-scripts/ifcfg-eth0 /etc/sysconfig/network-scripts/ifcfg-eth0:0
nano /etc/sysconfig/network-scripts/ifcfg-eth0:0

Change device name, set new IP, remove reference to hardware


DEVICE=eth0:0
BOOTPROTO=static
BROADCAST=172.16.0.255
IPADDR=172.16.0.3
NETMASK=255.255.255.0
NETWORK=172.16.0.0
ONBOOT=yes

Pause a Linux Shell Script using Sleep

It’s easy to pause a shell script during execution. Just add:

sleep 10

(where 10 is the number of seconds you want the script to pause.)

Some code for testing would be…

#!/bin/sh
before="$(date +%s)"
echo $before
sleep 3
after="$(date +%s)"
echo $after
elapsed_seconds="$(expr $after - $before)"
echo Elapsed time for code block: $elapsed_seconds

Have other ideas? Please comment.