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In the wake of shellshock

So, shellshock. It’s big. I think it’s bigger than heartbleed, because the bug has been in the code for 22 years, so there are an awful lot of systems out there with a vulnerable shell installed and nobody maintaining them properly. One misconception I’ve seen posted across the web is that you’re not in trouble if you don’t use bash as your shell, or that you’re safe if you have dash as /bin/sh.…

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Learning from Apple's goto fail

I’ve seen multiple posts drawing lessons from [Apple’s goto fail](). However, they’ve all focused on one or two issues that led to the error. I think there were a good half a dozen problems that led to the error, so here’s my summary. Problem 1: Braces The first problem, and the one most people pick up on, is the use of statements outside of code blocks in control flow statements.…

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Network Manager failing to recognize ethernet

Problem description: Network Manager refuses to start your Ethernet connection using the GUI, with the connection showing up as “Unmanaged”. The command-line interface to Network Manager reports an error “Error: Connection activation failed: Device not managed by NetworkManager or unavailable”. However, ifup/ifdown successfully starts and stops your Ethernet connection. Solution: Edit /etc/network/interfaces. Comment out any lines referring to eth* devices. Restart Network Manager via /etc/init.…

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Going back to something that works

Last week I had a bad experience with several pieces of office software. It started with a simple enough task: I had some existing documentation, and I needed to extend the “How to perform common tasks” section. There were two sub-headings to add, each of which needed a few bulleted paragraphs of instructions. I fired up LibreOffice, opened the document, and started typing — but something was wrong. When I clicked to turn my instructions into a bulleted list, the indentation was wrong.…

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The fractious leap second debate

You might not have heard about it, but there’s a debate going on which threatens to redefine time as we measure it. I’m something of a time nerd; all the computers in our house are synchronized to atomic clocks, as are several of our regular clocks, my wristwatch, and my phone. The debate going on concerns leap seconds. To understand the importance of it, it’s necessary to understand what a leap second is.

Recording time is made difficult for us by the fact that we live on a large rotating object with high mass, in orbit around a star. We like our time measurements to correspond to the apparent observed motion of the star in our sky; in short, we like day to be light, and night to be dark. We also like to set our calendar based on the earth’s orbit around the sun, so that winter is always cold and summer is always hot.

Inconveniently, the earth does not make an exact number of rotations per year. Hence every now and again it’s necessary to have a leap year, inserting an extra day into the calendar to bring it back into sync with the earth’s orbit, so that the months don’t gradually drift against the cycle of hot and cold weather.

The problem of wanting day to be light is solved by having time zones, with different parts of the world choosing a different offset in hours so that noon is roughly when the sun is overhead.

Historically, the offsets were measured from GMT, time as measured at the Greenwich Observatory in England, calculated from the position of the sun. However, the development of atomic clocks of increasing accuracy, and telescopes of increasing power, made scientists aware of problems with this simple scheme.

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