Tips, Tricks and Information for the Modern Technologist

Category: Configurations


Apache 2.4 Upgrade and the “Invalid Command ‘Order’” Error

Posted 6th March in Configurations. No Comments

The new Apache 2.4 has been released a few weeks ago and I decided to use this version while installing a new server (I compiled it from scratch rather that using an rpm or deb). After using one of my tried and true Apache configuration files, I received this error on start: 12Starting httpd: AH00526: [...]



The Easy CIDR Cheatsheet

Even though I’ve been working with Classless Inter-Domain Routing (henceforth known as CIDR) for years now, I always need a bit up a help remember how many addresses are in each block and how many sub-blocks fit into larger blocks. I have the following printed out for easy reference, and here it is for your geeky enjoyment:

CIDR        Total number    Network             Description:
Notation:   of addresses:   Mask:
--------------------------------------------------------------
/0          4,294,967,296   0.0.0.0             Every Address
/1          2,147,483,648   128.0.0.0           128 /8 nets
/2          1,073,741,824   192.0.0.0           64 /8 nets
/3          536,870,912     224.0.0.0           32 /8 nets
/4          268,435,456     240.0.0.0           16 /8 nets
/5          134,217,728     248.0.0.0           8 /8 nets
/6          67,108,864      252.0.0.0           4 /8 nets
/7          33,554,432      254.0.0.0           2 /8 nets
/8          16,777,214      255.0.0.0           1 /8 net (Class A)
--------------------------------------------------------------
/9          8,388,608       255.128.0.0         128 /16 nets
/10         4,194,304       255.192.0.0         64 /16 nets
/11         2,097,152       255.224.0.0         32 /16 nets
/12         1,048,576       255.240.0.0         16 /16 nets
/13         524,288         255.248.0.0         8 /16 nets
/14         262,144         255.252.0.0         4 /16 nets
/15         131.072         255.254.0.0         2 /16 nets
/16         65,536          255.255.0.0         1 /16 (Class B)
--------------------------------------------------------------
/17         32,768          255.255.128.0       128 /24 nets
/19         16,384          255.255.192.0       64 /24 nets
/19         8,192           255.255.224.0       32 /24 nets
/20         4,096           255.255.240.0       16 /24 nets
/21         2,048           255.255.248.0       8 /24 nets
/22         1,024           255.255.252.0       4 /24 nets
/23         512             255.255.254.0       2 /24 nets
/24         256             255.255.255.0       1 /24 (Class C)
--------------------------------------------------------------
/25         128             255.255.255.128     Half of a /24
/26         64              255.255.255.192     Fourth of a /24
/27         32              255.255.255.224     Eighth of a /24
/28         16              255.255.255.240     1/16th of a /24
/29         8               255.255.255.248     5 Usable addresses
/30         4               255.255.255.252     1 Usable address
/31         2               255.255.255.254     Unusable
/32         1               255.255.255.255     Single host
--------------------------------------------------------------
Reserved Space:
	0.0.0.0/8
	127.0.0.0/8
	192.0.2.0/24
	10.0.0.0/8
	172.16.0.0/12
	192.168.0.0/16
	169.254.0.0/16

Disabling The hald-addon-storage Service On CentOS/RedHat

The hald – Hardware Access Layer Daemon – runs several processes in order to keep track of what hardware is installed on your system. This includes polling USB Drives and ‘hot-swap’ devices to check for changes along with a host of other tasks. You might see it running on your system as follows: 12342474 ? [...]


How to Install SNMP on Tomato Router Firmware and Graph Traffic with Cacti

You’ve flashed your old WRT54G or other vanilla router with the Tomato firmware. This itself turns your router into a lean, mean routing machine with QOS, SSH and more, but let’s say we want to take it a bit further. What it we want to get some more stats out of it? In order to [...]


A Twitter Search WordPress Plugin

Ok, this is not really a plugin per se, but WordPress already has the capability of displaying a Twitter search stream via it’s RSS feed widget. It is dirt simple to set up. Go into Appearance -> Widgets and select the widget area you wish to add the twitter search stream to; Add “RSS” and [...]


Password Protected Folder Gives 404 Not Found in WordPress Installation Sub-folder.

Came across this little maddening issue again today after fixing it a few months back. I created a directory that is password protected using a .htaccess file. However, when trying to access this folder or anything under this directory, a File Not Found 404 error from WordPress is displayed before it even prompts you for [...]


Installing And Compiling Zabbix Client / Agent

Zabbix is an excellent system monitoring package. It does everything from basic availability checking to detailed system resource analysis. It is capable of graphing the variables pulled from the system, and alerting admins if there is a problem or something needed for attention. Once you have the Zabbix server set up, you need to install [...]