On the other hand, I really miss the WordPress interface. I have been blogging with WordPress for so long that I seem to write better posts using the WordPress interface than I can anywhere else. I am definitely a creature of habit.

I wonder how a map would look in the middle of this post?

Source: Wikipedia

Then one of my co-workers found AllElectronics.com and we found an adapter that works. It was $17 shipped and it works just fine on my EeePC. The model number is PS-930 and you can buy it here. It is a 9V adapter wth a 3A draw and it performs wonderfully. Hope this helps someone.

This means that should your database fail, and someone would open your front page at example.com, he would be served that error page with a 200 OK header. If that someone were a search engine, that’s what it would index… If the search engine encounters a 500 error, it will not index that page and just wait for your server to be fixed again. That means not making sure it sends a 500 header is a huge risk.

Source: Wikipedia

In the related articles below are links that explain the recent changes in the Safari license that *now* allows Windows computers to run Safari.

rrdtool

background…

my home network is built upon a wireless LAN using Orinoco RG-1000. however, the network performance from my linux server to Internet is poor due to the server location is separated from a ‘thick’ concrete wall. i need some tools to monitor the details such as signal strength, link rate… etc.

mrtg is the first things come to my mind. i search thru google.com and discovered Martin from Western Austrila has already do a great job using rrdtool.

mrtg has a long history in the Net and many people are using it around the world. mrtg does not only collect data every 5 mins, but also generate graph every 5 mins. the graph generation is cpu & io intensive and it limited the scability of mrtg. author of mrtg reimplement mrtg as rrdtool (round robin database) and it separated data acquisition and presentation.

my idea…

Martin from Western Austrila have a good demo how rrdtool integrate to monitor linux wirless interface. martin also indicated that mrtg cannot be used to measure negative and fraction value, but rrdtool can. however, martin’s script required server to generate graphs every 5 minutes and store them into disk.

i rewrite the code and separate the task of data collection and graph generation. perl script is used to collect data and store it into rrdtool database. php will be used as a server script to generate graph on-demand. i called it drrdgraph (dynamic rrdgraph). it should be easy to integrate into your webpage or add you customer code to limit the access of graph.

screen shot…

here’s a screen shot of dynamic rrdgraph page. it has a similar look of mrtg!!

requirement…

you’ll need…

• a linux box with wireless interface and apache running
• a rrdtool rpm or tarball
• php 4.0 above installed
• my dynamic rrdgraph

i install redhat 8.0 on my linux box and it recogized my Orinoco siliver card during installation. however, if you have problem on wireless interface, have a look at linux wireless lan howto.

hints: support on usb-based wireless card is limited. if your desktop/laptop have pcmcia adapter, get a wireless pc card. i prefer ISA-based pcmcia adapter especially for compaq desktop as there is problem on ricoh chipset, PCI-based pcmcia adapter. trust me, i try it on my compaq already.

installation…

installation of rrdtool is straightforward. if you got rrdtool tarball, untar it and follow README instruction. if you are using redhat, simply get the rpm package and type…

rpm -Uvh rrdtool*.rpm

you should download dynamic rrdgraph, untar it under your html root document tree. four perl scripts for capturing cpu, ethernet traffic, wireless and memory usage are included as examples. you should move them to /var/rrd/ and chmod 755.

mkdir /var/rrd/
mv script/* /var/rrd/
chmod 755 /var/rrd/*

creating database…

same to marty website, i also use the same rrdtool database to store wireless data such as SNR, signal, noise and link rate details. Here’s the command to create the database…

rrdtool create /var/rrd/eth1w.rrd -s 300	\
         DS:snr:GAUGE:600:0:60			\
         DS:signal:GAUGE:600:-105:-50		\
         DS:noise:GAUGE:600:-105:-50		\
         DS:rate:GAUGE:600:0:11			\
         RRA:AVERAGE:0.5:1:576			\
         RRA:AVERAGE:0.5:6:672			\
         RRA:AVERAGE:0.5:24:732			\
         RRA:AVERAGE:0.5:144:1460

four data sources (snr, signal, noise and rate) are created and this command create four aggregates too (2-day of 5-min average, 2-week of 30-min average, 2-mount of 2-hour average and 2-year of 12-hour average). please refer to rrdtool create” manpage for details explanation.

collecting data…

configure the following perl script eth1w.pl and make sure path and interface are good to your system.

# define location of rrdtool binary
my $rrdtool = '/usr/bin/rrdtool';
# define location of rrdtool databases
my $rrd = '/var/rrd/eth1w.rrd';
# define the wireless interface
my $iface = 'eth1';

run the script. if it’s good, you should get the following output.

> /etc/rrd/eth1w.pl
eth1 link stats: snr: 22 dB, signal: -76 dBm, noise: -98 dBm, rate: 5.5 Mbits/s

to automate the data collection, schedule the script to run every 5 minutes by setup a cron job. edit /etc/crontab and add…

# rrd
# get wireless link details (snr, signal, link rate)
00-59/5 * * * * root /etc/rrd/eth1w.pl > /dev/NULL

viewing graph…

edit config.php and make sure path is correct to your rrd database. samples for wireless, cpu, memory usage and ethernet traffic are included.

use your favourite web browser and select drrdgraph.php. a dropdown menu should be available for your selection for graph display.

it’s also easy to put the code inside your portal or add your authorization code for per user view. i integrate drrdgraph here and you could see my server statistic online.

other databases used…

you can use your imagination to create round robin database to store the data and display it thru my drrdgraph. commands for creating other rrdtool database are also shown here for your reference.

cpu0.rrd- three datasources are created using DERIVE. lower and upper values are set as 0 and 100 respectively (percentage).

rrdtool create /var/rrd/cpu0.rrd -s 300	\
         DS:user:DERIVE:600:0:100	\
         DS:nice:DERIVE:600:0:100	\
         DS:system:DERIVE:600:0:100	\
         RRA:AVERAGE:0.5:1:576		\
         RRA:AVERAGE:0.5:6:672		\
         RRA:AVERAGE:0.5:24:732		\
         RRA:AVERAGE:0.5:144:1460

eth1.rrd- two datasources are created using DERIVE. lower and upper values are set as 0 and 10^6 respectively (10^6 = 1000000 = 1m).

rrdtool create /var/rrd/eth1.rrd -s 300	\
         DS:in:DERIVE:600:0:1000000	\
         DS:out:DERIVE:600:0:1000000	\
         RRA:AVERAGE:0.5:1:576		\
         RRA:AVERAGE:0.5:6:672		\
         RRA:AVERAGE:0.5:24:732		\
         RRA:AVERAGE:0.5:144:1460

mem.rrd- i use a single database to store main memory and swap memory so there are four datasources created as GAUGE. lower and upper values are set as 0 and 10^9 respectively (10^9 = 1000000000 = 1g). if you have more memory, set the upper limit to higher.

rrdtool create /var/rrd/mem.rrd -s 300		\
         DS:memused:GAUGE:600:0:1000000000	\
         DS:memfree:GAUGE:600:0:1000000000	\
         DS:swapused:GAUGE:600:0:1000000000	\
         DS:swapfree:GAUGE:600:0:1000000000	\
         RRA:AVERAGE:0.5:1:576			\
         RRA:AVERAGE:0.5:6:672			\
         RRA:AVERAGE:0.5:24:732			\
         RRA:AVERAGE:0.5:144:1460

download

you can download and integrate drrdgraph from here

my server stat

you could see demo at my server statistics. let me know if you have any comment on the php!!

But just like the little bee in that one music video, I know there exists a place for people just like me. If anyone has any ideas, please email me at:

or at twitter as nogrrlsallowed.  Thanks!

The present article is an attempt to prove to you that, on price alone, the Mac is not the BMW of computers. It is the Ford of computers. I am not arguing that the Mac is cheaper only if you consider the psychic benefits conferred by its quality. Rather Im going to illustrate something more straightforward: Even though you may pay a slight premium at the cash register for a Mac over a comparable Windows PC a premium that gets slighter all the time, it will cost you less money — real, honest-to-goodness American dollars — to own that Mac than to own that PC.