الْحَمْدُ لِلَّه, Fedora 16 has been released!  You can read the full release notes or just go straight to the torrents for downloading.  See the release announcement after the fold…

The Fedora Project is pleased to announce the release of Fedora 16 (“Verne”). For detailed information, see the release notes:

http://docs.fedoraproject.org/en-US/Fedora/16/html/Release_Notes/

Fedora is a leading-edge, free and open source operating system that continues to deliver innovative features to many users, with a new release about every six months. Fedora 16 brings exciting new features for desktop users, for system administrators, and for developers. Highlights of these features can be found below. If the mere mention of Fedora 16 is all you need, download options can be found at:

http://fedoraproject.org/get-fedora

Dedication

During the preparation of Fedora 16, the computing world lost one of its great contributors: Dennis Ritchie. Ritchie co-invented Unix and the C language. He also co-authored The C Programming Language, a book that taught many programmers just at the time personal computing was exploding. Without Ritchie computing would be nothing like it is today.

A humble man, not well-known outside his field, Dennis will always be remembered by those of us who practice the craft. Thank you, Dennis.

What’s New in Fedora 16?

For desktop users

A journey to the center of the desktop:

• GNOME 3.2, the latest update to the most popular desktop environment, brings new features, including:
  • System Settings gains an “Online Accounts” panel, which provides a central point for managing online accounts like Google, Facebook, etc.
  • A new contact management application is integrated with Empathy, Evolution and the new “Online Accounts” settings panel
  • A new document management application provides a simpler alternative to traditional file management for both local and “in-cloud” documents.
• KDE 4.7, the most recent version of this feature-rich desktop environment, brings substantial updates, including:
  • DigiKam 2.0 adds face detection and recognition, geotagging and more.
  • An updated Plasma Workspaces window manager (KWin) makes KDE better suited for mobile devices, and also adds improvements for desktop users.
  • A new shutdown dialog allows users with multiple operating systems to select the OS to boot next.

For developers

Twenty thousand lines in C:

• Perl 5.14, a new version of Perl, brings many enhancements, including Unicode 6.0 support.
• GCC Python Plugins extend GCC with Python 2 and 3, without dealing with the C internals of GCC.
• D2: Fedora 16 is the first Linux distribution to include the newest version of D, a systems programming language combining the power and high performance of C and C++ with the programmer productivity of modern languages such as Ruby and Python.

For system administrators

Around the world in eighty columns:

• GRUB2: This leap forward allows better configuration options and better support for non-x86 architectures.
• New system account ID numbering: Fedora 16 starts user IDs at 1000, providing more room for system accounts and making it easier for administrators not have services run as root. This improves interoperability with other Linux distributions that start user IDs at 1000.
• Chrony: Chrony provides network time protocol (NTP) client and server pieces which are more tolerant of unstable clocks and Internet connections which are not always on.
• ext4 driver mounts ext2 and ext3: Fedora 16 uses the ext4 driver to mount ext2 and ext3 file systems, reducing the size of the kernel code.
• Improved virtualization tools:
  • Fedora 16 provides improvements to virtual networking, making large deployments easier.
  • Virt-manager guest inspection is a unique-to-Fedora tool allowing read-only access to guest file systems, applications, and Windows registry.
  • Fedora 16 provides locking of virtual disks to prevent a disk being used by multiple virtual machines simultaneously.

This is only a taste of what is included in Fedora 16. A more detailed list can be found at:

https://fedoraproject.org/wiki/Releases/16/FeatureList

Alhamdulillaah, I’ve discovered a new WordPress blogging client packaged with Fedora – namely, Lekhonee. There aren’t a lot of formatting options, but it appears you can post using HTML, so that’s a plus, I think. Let’s see how it goes.

Alhamdulillaah, the Fedora Project has released Fedora 11!  You can get the torrents and/or check out the new features!

(Sorry for the rather uninspired & lazy post…I usually like to share more details, but I’ve got work to do…;) )

Alhamdulillaah, I am quite pleased with the following HDR image I was able to assemble.  While not as good as the best that are out there, it is definitely a step-up from my other attempt I shared here.

HDR Scooter

The workflow this time was almost the same as always, with one minor difference.  I took several shots of the same scene at different exposure levels (1/3 EV), amounting to a whopping 28 (!) separate exposures, which is about the most I’ve ever done.  I renamed the images so that they were in sequence from darkest to lightest, which helps with the next step, which is to align them using Hugin‘s separately-packaged align_image_stack.  However, instead of using the align_image_stack utility directly, I called it from within Qtpfsgui (using the –align switch on the command line).  I used the default HDR generation settings and output to OpenEXR format.

The difference is that I did the HDR generation from within Qtpfsgui rather than using align_image_stack’s own routine (which also outputs in, I believe, Radiance HDR format).  Comparing the two, I realized that there wasn’t much difference at first, but at a closer zoom (e.g., 1:1), the Qtpfsgui method has far less noise in some areas (but not without some glitches, maybe you can find them), resulting in a smoother & more-natural picture.  I may consider playing with more than just the default HDR parameters with Qtpfsgui for generating the HDR image to see what other results I can get.

The final phase is tonemapping, which I generally don’t tweak.  Contrary to previous attempts, the Mantiuk algorithm produced a very colorful image, which I usually can only get with Fattal, which brings with it some other complications.  All in all, it was great.

If I had to guess, I would say that part of the reason for the ease of working with this HDR sequence was that the image had plenty of HDRness available to play with – the sky, the ground, the scooter with its reflective highlights as well as its darker spots.

Alhamdulillaah, to my pleasant surprise, I discovered that I started using Fedora personally with Fedora Core 4, and not 5 like I had previously thought.  This makes me feel better as I’m glad I started using Fedora earlier, because I like to think I recognized the importance of a completely (or as close as possible) free operating system (free here means freedom, not just free of cost).

At the time, I was content running it as a dual-boot system and just playing around with it.  By the time Fedora Core 5 came around, though, I was giving serious thought to using Fedora (Core, at the time) as my primary OS.  The complete transition happened, I believe, with Fedora 7 (which is also the year that Fedora Core & Fedora Extras combined, creating…Fedora!), where I relegated Windows XP to just being a spare OS for the very few things it does that I am unable to do with a completely free operating system (yet).

My experience with Fedora Core 4 was overwhelmingly positive.  I am sure I was impressed by the sheer amount of Free Software that was available for it as well as the elegance of a system that was not originated in Redmond.  I was and still am very pleased with the way Gnome works, and that was a big factor for me at the time as it is now.  I do wonder, though, if I downloaded & installed Fedora Core 4 today, what my experience would be link….hmm…

I remember seeing Fedora first in use as Fedora Core 2, when I was surprised someone was using it, as the name “Fedora Core” made me think it was the core of an operating system, but not the complete one.  I don’t know how or why I picked that up, but it is likely related to the perception that Fedora is not really meant to be used, and it is just a development platform (a blatantly false accusation).  I do know that I heard of Fedora Core when it came out, but again, my perception was likely incorrect at the time, thus causing me to adopt using it until quite late.  I had been using different GNU/Linux distributions since I was a freshman in college (can anyone say 1999?).  At the time, I recall trying “Corel Linux” – yes, I…don’t know what I was thinking.  I do remember it being based on Debian, though.  I also remember it significantly for a large amount of disk activity.  I don’t remember much else other than me deleting it shortly afterward.    Other flavors of GNU/Linux I tried were Red Hat, and that’s about all I can remember now.

So, anyway, this might be a good idea for a meme.  My first Fedora.  Talk about when you first started using it, why you did, and how the experience was.

Alhamdulillaah, I’ve just managed to produce my first HDR (high dynamic range) image the results of which I’m pleased with.  Once again, I have CHDK to thank for enabling this feature easily.

Note:  I begin this post with a mildly detailed explanation of the human visual system, HDR & LDR images, and the process to create HDR & tone-mapped images.  The pictures themselves are near the bottom of this post.

First, a little background about HDR.  The way our bodies capture and process imagery is, to put it lightly, amazing.  Starting from when light first hits the cornea through to when we perceive the visual object (not to mention how our brain’s store such visual images, which is far from just keeping a “bunch of bits”), the Words of Allāh resound with truth regarding His Creation:

And it is He who spread the earth and placed therein firmly set mountains and rivers; and from all of the fruits He made therein two mates; He causes the night to cover the day. Indeed in that are signs for a people who give thought. (Alqurʾān 13:3)

Thus, in the way that they are created, our eyes can capture an amazing amount of detail and range in their own way.  The range of regular (so-called “LDR” – low dynamic range) images is quite limited in comparison.  And this is, actually, the vast majority of image-related technologies, be they cameras, display devices, or even image formats such as JPEG.

HDR images, however, are those which do or have the ability to capture image details, specifically color & brightness information, at a much higher level than normal technologies.  Since normal technologies, such as our digital cameras and screens, can not capture nor display HDR images, we have to take a different route to get the information.  One technique is exposure bracketing where one takes a picture of the same scene at different exposure levels, one after another.  The reason for doing this is that, while the normal dynamic range of a camera may be unable to capture the bright, medium, and dark details of an image all at once, it does have the ability to capture these details separately with different settings.

Alhamdulillaah, there is also software that exists that allows you to take these separate LDR images and combine them into one now-HDR image that contains the details from all the separate exposures.  Doing so is not trivial, and it may take one multiple attempts to get something that looks good.  More often than not, the result is eery, because of a technique called tone-mapping.  Tone-mapping is a technique whereby the colors and range of an HDR image are brought down into a simulation of what our eyes would perceive in the scene.  In reality, that’s all but impossible, but it yields some interesting, beautiful, and sometimes striking results.

The specific software I use is the unpronounceable Qtpfsgui (I just say it one letter at a time).  Qtpfsgui is a front end for pfstools, which is an outstanding image toolkit for these kinds of images.  It takes care of aligning, merging, and finally tone-mapping the images one step at a time.  I short-circuited the first two steps (because Qtpfsgui can be fussy sometimes)  by using the command-line tool align_image_stack to align the different exposures (since I moved a bit between exposures) as well as creating the HDR image from the three separate images.  Then, I used Qtpfsgui just for the tone-mapping stage.

The first row of pictures are the original images, taken at -4, 0, & +4 EV settings.  Looking closely, you’ll notice that each range brings out different details: the darkest shows details in the clouds, the middle shows details in the sea, and the brighest shows details in the sand.  These are the separate LDR images at different exposures that I talked-about above.

The second “row”, containing only a single picture, is the result of the several steps I mentioned above to produce an HDR image.  I make no claims into how “real” this image looks, but it does show the details that I was looking for – from the clouds to the sand – in one image.  I also think it looks cool. 

This is the first HDR image I’ve created that I’ve wanted to share, and so I took this opportunity to explain the process too.  If you have any questions, then by all means, please post a comment and then subscribe to the comments so you’ll know when I’ve replied.

Note: This is for future reference as I try to make some progress on an old project.  I do not think the last value is a default for Fedora, but rather, something added later.  If someone knows otherwise, please correct me!

Update: I’m starting to dislike fixed-width templates…corrected the last $PATH value so it will fit on my blog without overflowing into CSS “Elsewhere”.

Update 2: Ahhh!  WordPress!  WYSIWYG, not WIWIWYG (What I Want is Why You Get)!

Note: This is a post I started writing back in November, but only got around to updating now.

Alhamdulillaah, I cannot believe I’ve lived for so long without knowing about screen (Wikipedia article).  To put it as simple as possible, think of screen as a “tabbed” interface for terminals/shells.  This is a weak analogy, however, because it enables so much more than tabs do for browsers, for example.  Onwards for more details.

History

I had first heard of screen through references and then through some of my friends, but I didn’t give it much heed because it seemed like something too complex for something so simple as a terminal application.  Little did I realize that, like most applications with their roots in Unix, it’s both simple and extremel useful.

Invocation

screen is invoked by typing it’s name.  It will appear initially as though you’ve reset your terminal, but this is just a new screen session, which is effectively a new login. Each screen window (which I will explain later) is independent and has it’s own scrolling buffer, independent also of your own terminal’s buffer. This means that screen as an application stores previously displayed text on the machine on which it is ran, so if you’re running it remotely, it won’t affect your local machine.

Basic Usage

Commands in screen are almost always prefixed by ctrl-a.  For example, creating a new window in screen is “ctrl-a c”.  Switching to the next window, if you have more than one, is “ctrl-a n”.  Previous is “ctrl-a p”.  screen windows can be exited by simply typing “exit” as if they were any other terminal session.  When the last screen window is exited, screen itself terminates.  Screen windows can also be killed by typing “ctrl-a K” (note the capitalization of “K”).

It’s also easy to jump to windows 0 – 9 by typing “ctrl-a” followed by the window number.  So, for example, if you want to jump to window 3 of your screen session, just type “ctrl-a 3″.

Detach and resume

The real beauty is using screen is its persistence.  Chances are, if you’ve used remote login shells frequently, you’ve been disconnected while working.  Most shells will respond by terminating whatever was actively running in the foreground of that terminal.  This means your vim session was interrupted.  It also means whatever service you had started is probably dead by now.  screen takes care of all of these things, because it behaves as a persistent application.  Thus, whenever you disconnect from the terminal, screen stays running, and it allows you to resume a previous screen session with the command line option “-R”, which means reattach an existing screen session, else start a new one.  Additionally, the “-d” argument might be useful, because it will detach the session from an existing login, in the case it is still attached elsewhere, such as a remote login from another location that you’re no longer using.

For example, if you are logged-in to your server from home with an active screen session, and then go to work, calling “screen -d -R” will detach the screen session from your home login and reattach it, where you left off, to your login from work.

Another advantage is that screen effectively allows you to make a daemon (background running process) from any command-line application, including those for which it normally isn’t possible.  An example of this would be rtorrent, which is a torrent downloading application normally meant to run in the foreground.  I personally like to start an rtorrent process running in one screen window and just leave it running.  Then whenever I login to that server and attach the screen session, I can check on the status of my torrents very easily by ctrl-a p/n to the appropriate window while doing other work.

Conclusion

So there you have it!  I realize this is a very introductory article with regards to screen, but it should be enough to get your started.  If you run into any problems with it, just type “ctrl-a ?” (that’s a question mark) and a friendly window will pop-up explaining, albeit briefly, all the different commands and what they do.