Open-Source Math Tool: Sage

So life as a student has begun.

But not quite the same. For instance, I still have work pending; I still have people chasing after me, I still have products in the pipeline while several hours daily, I am usually in class.

Several days ago, professors from maths class that I'll take next semester (next semester, mind you!!!), emailed us 4-pages "diagnostic" test of our level of mathematics. I swear cold chills descended upon my spine. Not that I hate math or anything like that, but it kinda reminded me of those days of math homeworks which took me hours to finish, not to mention those blasted complicated sums which sometimes, unfinished, crept into my sleep...

So I turned to wikipedia to refresh my 'math memory' - if there's such a thing, and lo and behold, it didn't turn out as difficult as I thought. Differentiation, all kinds of techniques to arrive at it, etc. wasn't quite as horrible as I thought. And then I discovered "Sage". After unsuccessful attempts to use Maple or Mathlab or something without paying thousands of dollars (hey I'm only a poor student), I discovered an open-source alternative. Somewhat thankful, I'd like to see how it compares to other packages. After several frustrating download attempts with a download speed in the range of 5Kbps, I finally found a mirror closest to where I am, that allowed the download (almost 400MB) to finish in about 20 minutes.

It's good enough for me to start writing this blog post :) Let's just say it appeals to the geeky part of me - it requires a mini-webserver to run at port 8000, and requires one to have accounts to 'log in', and its worksheet, was clean enough that I could verify my answers to a complicated differentiation in half an hour. Intuitive words such as "diff" and "sin" and "cos" simply work. Well, they need brackets. And I suppose a few helpful buttons wouldn't hurt. But hey, engineers love command-line interface, right? This package has all that we can ask for...

Just thought to recommend this nifty package.

Now back to the books...

Unveiling iPhone

After a release of an iPhone by Cisco some months ago (which turns out to be an VoIP phone), the rumor of Apple's release of a mobile phone (also branded iPhone) is finally proven to be the real deal!

A cursory glance reveals that it has all the making of an Apple product: sleek, elegant, and (this is yet to be checked out) avant-garde technologically. Its camera is 2MP. I'm not sure how powerful is the chip it runs on (it's a PortalPlayer chip), but get this: it runs Mac OSX!

While I'm not crazy about Apple products (I don't even own an iPod and don't intend to), this one got me drooling! Mac OSX is almost as good as having linux on your phone! Time will tell how far we could tinker with this baby.

Read more about it here.

Another goodbye?

I'm writing this post from my beloved linux workstation... I think this may be one of the last few ever made from this machine :(

It's been awhile since this machine worked smoothly; it's now having problem just booting up & showing anything on the monitor. It could be the video card (earlier I thought it was the monitor I have at home—that was also dying!), it could be the AGP port on the motherboard... Whatever it is, I shall miss it when it finally dies.

Goodbye ;~)

I never got around to naming my servers. Last night we completed migration from the last of the old Linux servers (named 189.. after the last triplet of its IP, how impersonal!) and this morning I found myself shutting down the server and doing an "rm -rf *" on my home directory as well as on the application directories.

[antonia@189 /home/antonia/]$ rm -rf *

Two weeks ago, we 'gave up' another Linux server (193, yet another impersonal name). Ahh.. to say goodbye to good and faithful servants is heart-rending :)

SELinux: is it really more secure?

If you're out of touch with recent Linux development (like me), chances are you might have encountered SELinux—Security-Enhanced Linux (probably in a bad way) while trying new distros or maintaining/updating your favorite packages.

I'm all for better security, having been a sysadmin in the past, but I must confess SELinux baffles. The idea seems simple enough: introduce security context for subjects (processes/users) and objects (files/devices), utilizing all 'the security-relevant information available', and not just rely on 'authenticated user identity'.

What I still don't understand (I'm a little lazy right now to sit & read through mountains of documentation) is how older programs and packages are supposed to work with SELinux? Last week I installed Qmail+Courier+Squirrelmail, and every individual package troubleshooting page would contain a note about disabling SELinux!

This is reminiscent of how J2ME security model ends up being an obstacle to user adoption rather than increase the sense of users' security when installing an application on their mobile...

More links here on SELinux.

Sunday afternoon work note

Some things never change:

- qmail still rocks

Some things always change:

- Keep yourself updated: My last three Linux OS server installations were in early 2004; there were two RedHat 9 machines and before that, Mandrake 10. Since then, all RedHat's products have now become commercial, so we're left to use minimally Redhat-supported Fedora. Mandrake has closed down and been renamed Mandriva!

- Fedora Core 5 ships and uses GCC 4.1. Some applications (quite a few of them, eg: Java EE 5 package) that were compiled with an older GCC 3.2 will require compatibility libraries (such as: compat-libstdc++-33, compat-libstdc++-296)

- In Fedora, yum is recommended for package installation instead of rpm.

- In Fedora, yum needs an OS key before it can install or update any package. Key needs to be obtained using:
rpm --import /usr/share/doc/fedora-release-X/RPM-GPG-KEY*

Note to myself: PHP, Pear, and HTTP_Request

Sometimes the plethora of scripting languages out there makes for a tough day... I have in the past, 'discovered' scripts to simulate HTTP form post/file upload from Java and Perl (the 2 languages I used most often in web scripts).

Today we're doing it (simulating file upload through HTTP form) from PHP. Simple enough?

require_once "HTTP/Request.php";

$req =& new HTTP_Request("http://myserver/myservlet");
$req->setMethod(HTTP_REQUEST_METHOD_POST);

$result = $req->addFile("myfile", "/myfile-full-location");

This gives error:
Failed opening required 'HTTP/Request.php' (include_path='.:/php/includes')

And for the next 2 hours, this little 'script' thing made me go through:

1. Install / re-configure PEAR
For PHP v5.0.3, PEAR comes preconfigured. But for some reason, I could not find 'Request.php' anywhere in the system using find.
Try this: upgrade a few installed packages; HTTP, Net_URL, Net_Socket and finally HTTP_Request. Also add the new path /usr/local/lib/php to the variable include_path in my php.ini file.
Your PHP does not support zlib?

2. Re-installation of PHP
This time, remember to configure it with these support flags: --with-zlib and --with-libxml (another roadblock: the version of libxml2 I had was too old).
Oops! Forgot the old configure flags --with-mysql and --with-apxs2.
Repeat this and repeat Step 1.

3. Still not working?
The message on the error page still hasn't changed! Wait a minute... I've recompiled & reinstalled PHP several times and nothing changes?
Try this: $ sudo apachectl graceful

Finally the problem is nailed... thank God!

I'm writing this note to myself just in case I need to open the car hood again :|

<rant>Everybody seems to run into this simulation process sometime. Why don't we make something new to spare the newer programmers and write a language-agnostic library or something?</rant>

Back to Linux: welcome back, evenstar!

These past two months I have been operating on a Windows machine at the office & at home (on a laptop) because my workstation's monitor has this need to 'rest' for a few weeks before it could power up... I feel absolutely schizophrenic!

Now I'm back on evenstar (my Linux machine) and oh boy, I can do so much more! ;)

"Hashing exploit threatens digital security"

From New Scientist: Hashing exploit threatens digital security

The affected algorithms potentially are MD-5 and SHA-1. This'd up the ante for the game of patch-and-hack... which reminds me of the rootkit episode!

When I wrote last week about getting rootkit-ed, I didn't mention that it was md5sum that helped me detect the changes made to the sshd binary. The attacker left a backdoor (/etc/ld.so.preload); creates a /tmp/getuid.so that returns 0 when login/ssh daemon tries to look up a user's UID. It was admittedly, not a very deep attack (it was not even a Loadable Module Kernel-style attack), and the attacker did not even attempt to erase his footprint.

(More description can be found here)

Yet, it is a disturbing discovery that requires yet more vigilance on the defender's part. That's one tool less to fight attackers out there.

Rootkit-ed!

My machine has been rootkit-ed!

Spent the entire day fixing it.
2nd lesson this year: take care of your old user accounts! :-(

Sysadmin blues

I really thought those days were over. I was naive of course; the job of maintaining the PCs in the company is primarily mine although I'd like to think of "my machines" as comprising of our 2 Linux machines and my own windoze workstation.

Well, well. This week, one (or more!) of our windoze PCs have been sending automated requests to google.com (constituting a DOS-pattern) and consequently our IP got banned by Google. Unfortunately, or fortunately, Google also blocks the NUS proxy IP, effectively blocking access to Google for the entire university population. Oh what horrors, all those students trying to find research materials or ready-made papers-for-sale online; all those research staff trying to do their job— suddenly cut off from their lifeline.

Really. When does Internet search become our lifeline? It's astounding how technology stealthily crept into our lives and quickly made itself indispensable. I suppose, other things must have been displaced from our lives just as stealthily too. This is something all companies need to look out for; we lounge about too long and our fate could be no worse than the dinosaurs of old.

Backtracking. Now all our machines' IP have been blocked. Will have to resolve the situation quickly; working with our campus sysadmins who are: (1) angry at us, no doubt, (2) stiff-nerdy-folks who are stingy with information.

Perfect day to begin the week of Lent :)

Solaris vs. FreeBSD vs. Linux

On a slightly less heavy-hearted topic, let's talk about OS-es :D yay, my next favourite subject!

Did I mention we've got a Solaris machine now? Our very own living breathing Solaris machine. An old baby, for sure, but a Solaris baby nevertheless. After the initial excitement has quietened, I realised that I've completely forgotten Solaris eccentricities. You see, Solaris was my 'rude' introduction to the NIX* world three years ago, and since then I have moved on to FreeBSD for servers and Linux for desktops.

Well, it's like getting re-acquainted to an old lover ;)

Another development at school:
'Revival' of Linux movement... of sorts.

When i was a freshman, there was a pretty active community of Linux users. They're the ones who were responsible of hooking me to this good stuff! Anyway.. times have passed, the machines in Linux lab have grown old and the OS unkempt.. so it's been shut down and made into (of all things sacrilegeous!) a Microsoft library!!!!!

Now a group of firebrand Linux evangelists (mostly a year my junior) have taken up the torch again, and they wanted to build a new Linux lab, have a Linux installfest and start a new Linux community. I will not, sadly, be there since I will (hopefully) graduate this April. But before then, I hope to give this group some worthwhile contribution. Viva le Linux!