Tips, Tricks and Information for the Modern Technologist

Category: Code Samples


Simple Disk Benchmarking in Linux Using ‘dd’

Posted 21st March in Linux, Shell, System Administration. 2 Comments

A great way to do a real-world disk test on your linux system is with a program called dd. dd stands for data description and is used for copying data sources. A simple command to do real-world disk write test in linux is: 1dd bs=1M count=512 if=/dev/zero of=test conv=fdatasync This creates a file named ‘test’ [...]


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

Exporting Announcements from WHMCS

Posted 6th September in Code Samples, PHP. No Comments

Doing some integration work with WHMCS, I found the need to export some of the announcements into Wordpress. Since there isn’t any native implementation of this, I found the best way is to export it directly from the database. The PHP code to do this is fairly easy…


What a Resilver Looks Like in ZFS (and a Bug and/or Feature)

At home I have an (admittedly small) ZFS array set up to experiment with this neat newish raid technology. I think it has been around long enough that it can be used in production, but I’m still getting used to the little bugs/features, and here is one that I just found.

After figuring out that I had 2 out of 3 of my 1TB Seagate Barracuda hard drives fail, I had to give the array up for a loss and test out my backup strategy. Fortunately it worked and there was no data loss. After receiving the replacement drives in from RMA, I rebuilt the ZFS array (using raidz again) and went along my merry way. After 6 months or so, I started getting some funky results from my other drive. Thinking it might have some issue as with the others, I removed the drive and ran Seatools on it (by the way, Seatools doesn’t offer a 64-bit Windows version – what year is this?).

The drive didn’t show any signs of failure, so I decided to wipe it and add it back into the array to see what happens. That, of course, is easier said than done.



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 ? [...]


Experimenting with Pascal on Ubuntu

Posted 21st February in Code Samples, Other Code, Ubuntu. No Comments

I’ve been busy lately on a number of projects, one of which is a programming class I am currently taking. The class itself is interesting, we are learning about the different types of programming languages. For our latest project, we were tasked with writing a simple program in Pascal. Pascal isn’t used too much any [...]