Cool image comparing star sizes

A story is in the news today about the European Southern Observatory (ESO) having discovered a star that is 260 times as massive as the Sun, exceeding what was thought to have been the maximum size limit of 150 solar masses for stars.  It is the largest star ever observed.  Accompanying the article is this startling image, which is an artist’s rendition of the comparative sizes of “R136a1” with other more standard-sized stars:

Whoa! Moma!

Very useful article on OpenSSH installation under Cygwin in Windows 7

Cygwin, sshd and Windows 7

WMAP Reassessment Casts Doubt on Standard Cosmological Model

Scientists have done some re-analysis of the ground-breaking Wilkinson Microwave Anisotropy Probe (WMAP) data which has been so important for cosmologists, and their re-assessment suggests that some of the interpretations of the data were off, thereby casting doubt on the entire standard cosmological model which includes the concept of dark energy.  In other words, this new reassessment indicates that dark energy – which has never been actually observed, only theorized – might not exist after all.

If that’s the case, then the fact that the expansion of the universe is accelerating is due to something else.  Possibly the theory of gravitation, which has not changed significantly since Newton’s time, needs to be fundamentally reworked.

Stop sitting up straight!

Imagine hearing your mother telling you this, or a school teacher.  Yet it may be the truth.

I always knew this!  LOL

Sitting straight ‘bad for backs’

On another note, I once heard somewhere that, in the time of Jesus, people used to eat laying on their sides, in a kind of lounging out position.  I’d love to see that come back.

Pronation, Explained: Info from Runner’s World Magazine

Pronation, Explained: Info from Runner’s World Magazine.

Extremely Cool Tool for Creating Live Linux USB Keys

Universal USB Installer by is a really cool utility which automates the process of creating a live Linux USB key installation.  With this utility, you can easily transfer a Linux live CD image to a USB key.  It supports various versions of Ubuntu/Kubuntu/Xubuntu, Knoppix, GParted, and many others.

All you have to do is download the iso cd image of the live Linux system you want, then copy the Universal USB Installer program into the same directory as the .iso, and run it.

I created a bootable Ubuntu 10.4 USB key with this utility in a few minutes.  It also has an option to set a persistence option for the system it installs, meaning that, unlike with a CD, you can actually read/write data on the USB key and save your customizations/configurations between reboots.

SOHO’s Successor

I had actually looked to see what was going on with solar missions with NASA and ESA, yet in my searching I had not found anything that appeared to be replacing SOHO, but then stuff on SDO has been popping up in the media lately, so maybe I missed it.  Today I found the main data page for SDO.  Wow.  Here is a list of instruments on the craft.  Unlike the SOHO which is in what is called a Lagrange halo orbit, SDO is in an inclined geosynchronous Earth orbit (GEO).  At least part of the reason for this, I have read, may have to do with data transfer rates, as SDO is transmitting much more information than SOHO.  Its actually interesting to know what the Sun-Earth Lagrange points are, and why the L(1) was chosen for SOHO.

image of SDO spacecraft

image of Sun taken by SDO

NOAA Gulf of Mexico Deepwater Horizon Incident Web Site

Deepwater Horizon Incident, Gulf of Mexico

As the nation’s leading scientific resource for oil spills, NOAA has been on the scene of the Deepwater Horizon spill from the start, providing coordinated scientific weather and biological response services to federal, state and local organizations.

Customizing Windows 7 Save/Open Dialog Sidebar Links

I just installed an extremely useful utility which was mentioned in a thread over at the excellent site.  It allows you to change the default links which show up in the left sidebar in the Open and Save dialog windows.  By default, the left sidebar for Open and Save dialogs contains the following five links:

Recent Places

What is annoying about this is the conspicuous lack of a link for the most obvious place that anyone would want to save to or open an item from: their My Documents folder.  Another obvious one would have been the user’s home folder (one directory above the My Documents folder), which contains the My Music, My Pictures, My Videos and other folders.

This problem is solved with the following utility: Simpli Software’s Places Utility.  With it, you can customize the 5 slots which occupy the left sidebar with whatever links you want.  One trick I will mention that is necessary for getting it to work is that the utility must be run as Administrator.  Even if your regular user has administrative privileges, it is not enough to make the changes to the system.  You must right-click on the utility’s icon and select “Run as Administrator” to run it.

95th percentile calculation with RRDtool

I’ve managed to come up with some useful scripts using RRDtool to pull data out of round-robin archives (rra’s) and to compute 95th percentile.  RRDtool is used as the database backend for multiple monitoring tools such as Cacti, Torrus, Zenoss, and MRTG (as option).

In working this out I utilized the benefit of having my own Cacti deployment handy so that I could compare syntax against Cacti’s own RRDtool queries.  Cacti is an excellent tool because it essentially provides a nice frontend for setting up the necessary SNMP polls to devices that create the rra’s in RRDtool which contain all the data points from the SNMP polls.  It then uses RRDtool queries to extract and process various data and to graph it.  It does a nice job of this without adding a layer of obfuscation on top of RRDtool and is extremely perspicacious, allowing you to see exactly what commands its running via its graphical web interface.

Extracting Data Points

Using the rrdtool xport command you can pull data points from an rra into XML format like so:

rrdtool xport DEF:xx="11_22_33_44_traffic_in_225.rrd":traffic_in:AVERAGE DEF:yy="11_22_33_44_traffic_in_225.rrd":traffic_out:AVERAGE CDEF:aa=xx,8,* CDEF:bb=yy,8,* CDEF:sum=aa,bb,+ XPORT:aa:"in bits" XPORT:bb:"out bits" XPORT:sum:"sum"

The output of this will look like the following:

<?xml version="1.0" encoding="ISO-8859-1"?>

          <entry>in bits</entry>
          <entry>out bits</entry>

What I want to do now is actually just extract the raw data set from this query and present it in a clean form.  This data can later be processed further, for example it can be output into csv format for processing somewhere else (might be useful if you are working on billing calculation methods for example).

To do this I only need two other tools, grep and the GNU version of awk, gawk:

rrdtool xport DEF:xx="11_22_33_44_traffic_in_225.rrd":traffic_in:AVERAGE DEF:yy="11_22_33_44_traffic_in_225.rrd":traffic_out:AVERAGE CDEF:aa=xx,8,* CDEF:bb=yy,8,* CDEF:sum=aa,bb,+ XPORT:aa:"in bits" XPORT:bb:"out bits" XPORT:sum:"sum" |grep -v NaN |grep -F -e '<row>' |gawk -F '<[^>]*>' '{printf "%s %10.3f %10.3f %10.3fn", strftime("%Y.%m.%d-%T",$3)" ", $5" ", $7" ", $9}'

The actual data points are contained in the lines embedded between the <row>  </row> tags.  I use grep to filter out entries with NaN values, which are data points which for one reason or another are empty (usually because the SNMP poll to the device did not return a result).  I then use grep to select only the lines with <row>.  This filters out all the XML header info at the top.

After grepping, the output will look like:


Next, I use gawk and specify the field delimiter as the brackets for XML tags using the regex  <[^>]*>
Finally, I print the fields in question (in this case fields 3, 5, 7, and 9, the other fields are various other non-data characters in the row.  If you are using a different rrdtool query with different CDEF’s or XPORT statements the fields may be different.)

Finally, I use some gawk magic to change the format of the first column of data, which is the epoch date (date given in number of seconds since 1 January 1970) to a more readable date.  Note that I chose a date format (using the strftime function)  which is still able to be sorted numerically (this would not be the case if for example the format was Jan 1, 1970 12:00).

The output will now look like:

2010.03.15-16:00:00  35909368.728 7704976.538 43614345.266
2010.03.15-16:05:00  34919549.475 8418161.515 43337710.990
2010.03.15-16:10:00  35540540.978 8270836.766 43811377.744

With the preceding output it is now trivial to use the cut command or some more awk to extract fields, or use the sort command to sort by certain columns.  For example:

sort -t ' ' -rn -k 3,3

will sort by column 3 in descending order.

95th Percentile Calculation

Here I am going to use rrdtool graph to output the 95th percentile calculation.  Without going into detail about how to define the necessary CDEF and VDEF statements (you can read in detail about these here), the following is the command I used:

rrdtool graph /dev/null -f ''  DEF:xx="11_22_33_44_traffic_in_225.rrd":traffic_in:AVERAGE DEF:yy="11_22_33_44_traffic_in_225.rrd":traffic_out:AVERAGE CDEF:aa=xx,8,* CDEF:bb=yy,8,* CDEF:totsum=aa,bb,+ VDEF:inper95=aa,95,PERCENT VDEF:outper95=bb,95,PERCENT VDEF:sumper95=totsum,95,PERCENT PRINT:inper95:"95th percentile bits in: "%lf PRINT:outper95:"95th percentile bits out: "%lf PRINT:sumper95:"95th percentile bits sum: "%lf

The output will look like:

95th percentile in: 46280432.074401
95th percentile out: 10138325.618306
95th percentile sum: 55849477.154300

Even though this uses the rrdtool graph command the output is to the console only. It is necessary to use the rrdtool graph command because you cannot specify a VDEF with rrdtool xport.

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