Category: Technology

For the last couple of weeks, my bedside reading has been this half-biography, half-autobiography on Linus Torvalds. I have to say, however, that the book is like two books mixed into one. Chapters alternate between Linus talking about his life and about big moments in Linux’s history to David Diamond describing modern-day Linus with a kind of forced wonder. Truthfully, Diamond comes off as a sycophant who couldn’t care less about Linus’s flaws and positive characteristics, and cares more about molding some kind of “image” of Linus as containing a humility and genius simultaneously. Near the end, I started only skimming the chapters not written by Linus. Diamond’s really not a good writer, either. (Sorry Dave.)

Truthfully, the book kind of pops the lid off Linux and makes you understand it as much less glamorous than say Wired Magazine described it to the public. Linus really just talks about not having a social life, sitting in his room with curtains covering his window, coding all day. Not exactly the ideal role model, I think. Don’t get me wrong, I love the Linux kernel (as much as one can love imperfect software), and Linus made a great contribution toward keeping the UNIX world and UNIX principles alive, but it’s just that I like to think of open source developers as something other than the stereotypical, introverted geek. In fact, much of Linus’s chapters is devoted to his apprehension about giving a public talk about Linux. When I think about the fact that I’ve given three or four of them to date, and enjoy it more every time, I see how different I am from this kind of stereotypical geek.

It also kind of made me dislike Linus. When I saw Revolution OS (a DVD on the rise of open source), the movie kind of endeared me to Linus’s practical nature as opposed to Richard Stallman’s religious idealism. I like idealism, but Stallman is really religious about it. And he’s bitter. Linus, on the other hand, has that great Northern European, “I’m just gonna go with the flow” attitude.

But this book made me realize that Linus is religious is his own sort of way. Included in the book is Linus’s flame war with Andy Tanenbaum on monolithic versus microkernel designs. Truthfully, I’ve studied operating systems and I’m not even sure which design is best, and Linus makes a decent argument of why microkernels end up being just as complex, or more complex than monolithic ones. But what I didn’t like is that in the flamefest, Tanenbaum said that deficiencies in MINIX were due to it being a hobby, and that he had duties as a professor. Linus responded, “Re 2: your job is being a professor and researcher: That’s one hell of a good excuse for some of the brain-damages of minix. I can only hope (and assume) that Amoeba [Tanenbaum’s future OS project] doesn’t suck like minix does.”

This just shows me that Linus really is an asshole sometimes. He states this outright in his book. So now, truthfully, I may like the open source movement, but I think I “at least dislike” two of its most major players (Torvalds and Stallman).

Finally, I think a clip from Tanenbaum’s website points out a nice principle in OS design:

Also, Linus and I are not “enemies” or anything like that. I met him once and he seemed like a nice friendly, smart guy. My only regret is that he didn’t develop Linux based on the microkernel technology of MINIX. With all the security problems Windows has now, it is increasingly obvious to everyone that tiny microkernels, like that of MINIX, are a better base for operating systems than huge monolithic systems. Linux has been the victim of fewer attacks than Windows because (1) it actually is more secure, but also (2) most attackers think hitting Windows offers a bigger bang for the buck so Windows simply gets attacked more. As I did 20 years ago, I still fervently believe that the only way to make software secure, reliable, and fast is to make it small. Fight Features.

I agree. But does a microkernel design actually reduce the overall size of the operating system, or does it just reduce the size of whatever you consider to be the “microkernel”? That is, just because a file system is implemented as a file system daemon talking to a driver subsystem through message passing doesn’t necessarily mean the file system, or driver subsystem, are secure. Insecurity could exist even at the boundaries, no? Not to mention instability.

I think Linus and Tanenbaum have to agree that this debate isn’t an open and shut case. The best kernel is probably one that mixes modularity, a strong kernel/userspace boundary, and some of the fancier features of a microkernel approach, while not sacrificing elegance of design or performance.

I’m organizing a group of people interested in hacking open source software in a team environment. Right now I’m calling it Free Coders at NYU, and have already set up a wiki and mailing list. This could end up being very cool. Next meeting is hopefully this coming Tuesday.

I set up a mailing list with GNU Mailman (link above), which was decently painless under Debian Sarge. The only annoying thing was utilizing my virtual e-mail address mappings which are stored in MySQL, but I figured out a trick for that.

I’ve already spoken, via e-mail, with an open source developer who works on gstreamer among other projects, Ronald S. Bultje. He has already tentatively agreed to do a talk for us sometime this year.

Just an interesting post I made to OSNews in response to someone saying that IE “starts quickly” while Firefox “takes forever.”

Just to clear up, the only reason IE starts faster in Windows is because IE is technically “always running.” The only thing that has to “start” is creating a Window with an “IE control” in it.

I get the same behavior on Linux by running galeon -s when my X session starts. This runs galeon in “server mode,” which means it’s always in memory, and when I run Galeon (on my laptop, I press ALT+F1 to run my browser), it starts in < a half-second. If Firefox had a similar mode, it could offer you the same thing. As for OpenOffice.org, it's true that the start time is relatively slow. I'm sure they'll get around to optimizing it. Personally, I think the obsession people have with start times on Linux and Windows machines is due to a basic design flaw with most Window managers. Applications should really only start up once; if you start an application multiple times in a day, you're essentially performing redundant computation. The program can sit in memory and if it really is not used in awhile, it will get paged out anyway due to our modern Virtual Memory implementations. In OS X, for example, you can get the same effect as "galeon -s" or IE's "preloading" simply by not quitting an application after all its windows are closed. This leaves the application running, and when you open a new window it will be nearly instantaneous. (Strangely enough, many old Windows/Linux freaks are sometimes "annoyed" by this aspect of OS X, since in the Linux/Windows world up to now, closing all windows of an application is equivalent to closing the application itself).

It turns out GNU ddrescue did just the trick, and I was able to get 98% of the data off that dead hard drive. Now to set up a new Windows system for these poor bastards (why, oh why, can’t everyone run *nix?). I need a cup of coffee first.

Wow. I hate when shit like this happens.

Apparently there are three tools out there to help with the same thing. First, there’s dd_rescue, the tool I was using earlier (which ships with Ubuntu in a debian package called… ddrescue). Then, there’s dd_rhelp, a shell script which is a frontend to ddrescue and which implements a rough algorithm to minimize the amount of time waiting on bad block reads.

Then, there’s GNU ddrescue, which is a C++ implementation of dd_rescue plus dd_rhelp.

I only just realized this and so now I’ve compiled a version of GNU ddrescue to pick up my recovery effort. It’ll probably help with one of the partitions that seems particularly messed up.

So far the nice thing about GNU ddrescue is that it seems faster, and more responsive. Plus, it has a real logging feature, such that if you enable it and then CTRL+C the app, you can restart it and it’ll automatically pick up where it left off.

UPDATE: wow, good thing I switched. GNU ddrescue is significantly faster just in terms of raw I/O performance. I jumped from 4GB of this partition being rescued (which took 30 minutes with dd_rescue) to 6GB in the last ten minutes. It seems at least 3x faster. I also like that the GNU info page describes the algorithmic approach in-depth.

So, one of my employers ended up with a fried hard disk, for the second time in a row. The main reason is that the PC this HD is contained in sits in a corner with little-to-no airflow.

In order to recover the drive, I am actually taking a different approach from my last recovery effort, mainly by necessity. This disk is seriously damaged–lots of bad sectors, and its partitions are not readable by any NTFS driver, be it Microsoft’s or the open source one. This makes simply using the wonderful R-Studio tool I used last time currently impossible, due to the fact that it won’t even see the drive properly within Windows, and will hang all over the place.

Indeed, what I needed to do is drop down a layer of abstraction: away from filesystems, and into blocks and sectors. Unfortunately, in the Windows world this drop down is difficult, so I had to use my Linux laptop to make this jump.

I found a wonderful tool to help me out called dd_rescue, which is basically a dd with the added features of continuing on error, allowing one to specify a starting position in the in/out files, and the ability to run a copy in reverse. These features allow one to really work around bad sectors and even damaged disk hardware to get as much data as possible out.

Unfortunately, the use of this tool was encumbered by my laptop’s relatively simple bus design. Apparently, if I stuck two devices on my USB bus (like two HDs I was using for this process), the bus would slow to a crawl, and the copy would move along at an unbearble 100kB/sec. I tried utilizing firewire and USB together, but got only marginal improvements. What befuddles me is that in the end, the fastest combination I could come up with is reading from the Firewire enclosure with my laptop and writing to the firewire enclosure of my desktop across the LAN utilizing Samba. Very strange indeed. Now my performance is more like 6MB/sec, factoring in all the breaks dd_rescue takes when it encounters errors. I have 6GB of the more critical partition written, but it’ll probably take a couple hours to have a big enough chunk that I can test R-Studio’s recovery of it.

The only reason I’m even writing about this is because I find it hilarious how many layers of abstraction I am breaking through to do a relatively low-level operation. Think about it:

1. My broken IDE drive is converted to Firewire by a Firewire-IDE bridge.
2. My Firewire PCMCIA adapter is allowing my notebook to take in that connection.
3. The Linux kernel is allowing firewire to be accessed via various ieee1394 ohci drivers.
4. The Linux kernel is abstracting the firewire disk as a SCSI disk, using emulation.
5. The SCSI disk is being read by dd_rescue and written to a file, which exists in the path /mnt/smb/image/sdb5.
6. That path seems local, but is actually a mount point. That mount point seems physical but is actually handled by a Samba driver.
7. The writes by dd_rescue to that image file are being sent through the kernel’s TCP/IP stack, and flying through my switch, and being accepted by Windows XP’s network stack.
8. Windows XP is writing that data to an NTFS drive, which is itself connected by a Firewire-IDE bridge (and therefore all the above steps’ equivalents for Windows apply).

I am surprised with that many layers, that this copy is even working. I really should have just taken a machine apart and connected these drives directly by IDE, to save myself a few layers.

I was just looking at my strange contact page, where I list my e-mail address using a sort of obfuscated string with _ and * characters mixed in. And then I saw someone’s e-mail address listed on the web with the following format:

user () domain ! com.

At that point, I started to think about all the other variations of this spam-protection trend I’ve seen, like user ///at\\\ domain ///dot\\\ com, and I realized that many of us are taking the wrong approach. Myself included. For example, the one above could easily be found by knowing the common TLDs and working backwards from there. If I find a “com”, “org” or “net,” and then look at the string tokens which occur before, I can assume any string of valid characters (say, alphanumeric characters) which is followed by whitespace or invalid chars (like parentheses and exclamation points) can be taken as a valid part of the address. From there, we can easily split user () domain ! com into its proper parts, and construct the e-mail. This same approach works for say, user ///at\\\ domain ///dot\\\ com.

So what I realized is perhaps it would be better to insert other e-mail addresses in there that might get picked up as part of an e-mail address, even in a heuristic scan. For example,

user __at__ domain :: NOT [email protected] :: __dot__ com

That seems more secure to me 😉 Another approach is just to prevent the TLD from being a complete token. This is the approach I took. Turn com into c_o__m or something, and you’re less likely to get picked up in a scan that is searching for “com”.

This /. article has responses from Microsoft Linux Lab manager Bill Hilf. I responded to this post from a Microsoft employee. My response follows. Continue reading Microsoft’s anti-competitive behavior

I wrote a pretty sweet script tonight. It parallelizes the getmail retrieval process, while still printing prefixes so I know which accounts download which messages. This means that instead of my mail fetching process taking sum(i₁,…,i_n), where i is the length of time for a given mail retrieval, my fetching process now takes max(i₁,…,i_n).

#!/bin/sh
GETMAIL='python2.3 -Wignore /usr/bin/getmail'
unwanted() {
  grep -E -v '(Copyright|getmail|Simple)';
}

echo "N-WAY GETMAIL RETRIEVER SCRIPT:"
$GETMAIL \
  --rcfile=/etc/getmail/account1 \
  2>&1 | sed -e \
  's/.*/account1................: &/g' \
  | unwanted &

$GETMAIL \
  --rcfile=/etc/getmail/account2 \
  2>&1 | sed -e \
  's/.*/account2................: &/g' \
  | unwanted &

...

$GETMAIL \
  --rcfile=/etc/getmail/accountN \
  2>&1 | sed -e \
  's/.*/accountN................: &/g' \
  | unwanted &

wait