The Author – Bart Busschots
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Sep
21
TTT Part 8 of n – Processes
Filed Under System Administration, Computers & Tech on September 21, 2013 | 6 Comments
For various reasons there’s been a bit of a gap between the previous instalment and this one. A big part of the reason is that I’d been putting off a lot of topics I wanted to talk about on Chit Chat Across the Pond until there was a logical break in this Terminal series. Having finished with the file system at the end of the part 7, I had my logical break point. Now it’s time to get stuck back in though, and start a whole new topic – processes.
We’ll start with a little history for context, then have a look at the model OS X uses to represent processes, and finish by looking at some commands for listing the currently running processes on your system.
Jul
19
TTT Part 7 of n – Managing Files
Filed Under System Administration, Computers & Tech on July 19, 2013 | 1 Comment
So far in this series we’ve focused mostly on the file system, looking at the details of file systems, how to navigate them, and at file permissions and metadata. We’re almost ready to move on and start looking at how processes work in Unix/Linux/OS X, but we have a few more file-related commands to look at before we do. In this instalment we’ll be looking at how to manipulate the file system, in other words, how to create files and folders, how to copy them, how to move them, how to rename them, and finally how to delete them.
Jul
13
TTT Part 6 of n – More File Permissions
Filed Under Computers & Tech, System Administration on July 13, 2013 | 7 Comments
In the previous instalment of this series we had a look at how standard Unix File Permissions worked. We looked at how to understand the permissions on existing files and folders, but not at how to change them. We also mentioned that the standard unix file permissions are now only a sub-set of the file permissions on OS X and Linux (OS X also supports file ACLs, and Linux has SELinux as an optional extra layer of security).
In this instalment we’ll start by biting the bullet and dive into how to alter standard Unix File permissions. This could well turn out to be the most difficult segment in this entire series, regardless of how big n gets, but it is very important, so if you have trouble with it, please don’t give up. After we do all that hard work we’ll end with a simpler topic, reading OS X file ACLs, and OS X extended file attributes. We’ll only be looking at how to read these attributes though, not how to alter them.
Jun
30
TTT Part 5 of n – File Permissions
Filed Under System Administration, Computers & Tech on June 30, 2013 | 1 Comment
In this instalment it’s time to make a start on one of the most important Unix/Linux concepts, file permissions. This can get quite confusing, but it’s impossible to over-state the importance of understanding how to read and set permissions on files and folders. To keep things manageable, I’m splitting understanding and altering permissions into two separate instalments.
Linux and Unix (and hence OS X) all share a common file permissions system, but while they share the same common core, they do each add their own more advanced permissions systems on top of that common core. In this first instalment we’re only going to look at the common core, so everything in this instalment applies equally to Linux, Unix, and OS X. In future instalments we’ll take a brief look at the extra file information and permissions OS X associates with files, but we won’t be looking at the Linux side of things, where more granular permissions are provides through kernel extensions like SELinux.
Jun
8
Photographing Satellites
Filed Under Photography, Science & Astronomy on June 8, 2013 | Leave a Comment
Ireland is actually quite far north, so our summer nights never get fully dark. You watch the sun set, but the glow on the horizon doesn’t go away, it slowly moves from the west through the north to the east where the sun rises again. This takes away a lot of astronomical opportunities, but, when one door closes, another opens. Because the sun never gets far below the horizon during the summer in higher northern latitudes, the part of space where satellites orbit remains in sunlight the whole night long, which means summer is satellite observing time! (The same is true in the southern hemisphere for far southern latitudes during their summer.)
There are lots of ‘ordinary’ satellites which can be seen pass over each night – they look like stars that move slowly but purposefully across the sky – taking a few minutes to cross from one side of the sky to the other. These can be fun to watch, and you can photograph them with a bit of effort, but, the stars of the show are the International Space Station (ISS), which blazes across the sky shining brighter than any star, and the network of Iridium communication satellites which ‘flare’ regularly. Any satellite can ‘flare’, when the sun glints off a solar panel or communication dish, but those flares are not predictable or dependable. Iridium flares are different, because the Iridium Satellites have massive dishes pointing earthwards at all times, and as they pass over-head, the dish will come into alignment with the sun, and what starts off looking like a regular dim satellite will suddenly brighten for a few seconds and then dim again. The flare is effectively a cone that sweeps the earth, if you are in the very middle of the cone, the flare will be spectacularly bright, down to magnitude -8. For context, the magnitude scale is inverse, so the lower the number the brighter the object. The brightest stars are about magnitude 0, the brightest planets about magnitude -4, and the Moon about magnitude -11, so -8 is getting close to the brightness of the Moon!
May
26
TTT Part 4 of n – Navigation
Filed Under System Administration, Computers & Tech on May 26, 2013 | 4 Comments
In the previous segment we discussed the concept of a file system in detail. We described how filesystems contain folders which contain files or folders, and we described the different ways in which Windows and Linux/Unix/OS X combine all the filesystems on our computers into a single name-space, within which every file has a unique ‘path’ (F:\myFolder\myFile.txt -v- /Volumes/myThumbDrive/myFolder/myFile.txt). In this instalment we’ll look at how to navigate around the Unix/Linux/OS X filesystem in a Bash command shell.
May
11
TTT Part 3 of n – File Systems
Filed Under System Administration, Computers & Tech on May 11, 2013 | 3 Comments
This is the third instalment of an on-going series. These blog posts are only part of the series, they are actually the side-show, being effectively just my show notes for discussions with Allison Sheridan on my bi-weekly Chit Chat Across the Pond segment on her show, the NosillaCast Mac Podcast. This instalment will be featured in NosillaCast episode 418 (scheduled for release late on Sunday the 12th of May 2013).
In the first installment we started with the 40,000ft view, looking at what command shells are, and why they’re still relevant in today’s GUI-dominated world. In the second instalment we looked at OS X’s Terminal.app, the anatomy of the Bash command prompt, and the anatomy of a Unix/Linux command. This time we’ll be looking at the anatomy of file systems in general, and the Unix/Linux file system in particular, and how it differs from the Windows/DOS file system many of us grew up using.
Apr
26
TTT Part 2 of n – Commands
Filed Under Computers & Tech, System Administration on April 26, 2013 | 3 Comments
This is the second instalment of an on-going series. In the first instalment I tried to give you a sort of 40,000ft view of command shells – some context, some history, a very general description of what command shells do, and a little bit on why they are still very useful in the modern GUI age. The most important points to remember from last time are that command shells execute commands, that there are lots of different command shells on lots of different OSes, but that we will be focusing on Bash on Linux/Unix in general, and Bash on OS X in particular. The vast majority of topics I plan to discuss in these segments will be applicable on any system that runs Bash, but, the screen shots I use will be from OS X, and some of the cooler stuff will be OS X only. This segment, like all the others will be used as part of my bi-weekly Chit Chat Across The Pond (CCATP) segment with Allison Sheridan on the NosillaCast Mac Podcast.
Last time I focused on the shell, and avoided getting in any way specific about the actual commands that we will be executing within the Bash shell. I thought it was very important to make as clear a distinction between command shells and commands as possible, so I split the two concepts into two separate segments. Having focused on command shells last time, this instalment will focus on the anatomy of a command, but will start with a quick intro to the Terminal app in OS X first.
Apr
13
TTT Part 1 of n – Command Shells
Filed Under System Administration, Computers & Tech on April 13, 2013 | 6 Comments
I have no idea whether or not this idea is going to work out, but on this week’s Chit Chat Across the Pond segment on the NosillaCast Mac Podcast (to be released Sunday evening PST) I’m going to try start what will hopefully be an on-going series of short un-intimidating segments to gently introduce Mac users to the power contained within the OS X Terminal app. I’m on with Allison every second week, and I’ll have other topics to talk about, so the most frequent the instalments in this series could be would be bi-weekly, but I think they’ll turn out to be closer to monthly on average. While the focus will be on OS X, the majority of the content will be equally applicable to any other Unix or Linux operating system.
In the last CCATP we did a very detailed segment on email security, and despite the fact that with the benefit of hind-sight I realise it was too much to do at once and should have been split into two segments, it received the strongest listener response of anything of any of my many contributions to the NosillaCast in the last 5 or more years. I hope I’m right in interpreting that as evidence that there are a lot of NosillaCast listeners who want to get a little more technical, and get their hands dirty with some good old-fashioned nerdery!
Dec
29
OS X Service for Stripping Geotags from JPEG Images
Filed Under My Projects, Photography, Software Development, Computers & Tech on December 29, 2012 | 1 Comment
Back in 2011 I wrote a blog post explaining how to create an OS X Service for stripping keywords from image files. In this post we’ll use the same technique to create a Service for stripping geotags from JPEG images.
As with the keyword stripping service, there are two prerequisites for this action, one is required, one is optional. You absolutely MUST have install EXIFTool installed, and it would be good if you also had Growl installed, but it’s not essential.