Jekyll2023-11-30T22:28:39+00:00http://richardlaugesen.com/feed.xmlRichard LaugesenWater models and decision scienceRichard LaugesenDestroy ZFS snapshots matching a keyword2021-03-22T00:00:00+00:002021-03-22T00:00:00+00:00http://richardlaugesen.com/destroy-zfs-snapshots-matching-keyword<p>I’ve got too many snapshots but I don’t want to delete them all. No one seems to have written down the required magic.</p>
<p>The following worked for me:</p>
<div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>zfs list -r -t snapshot -o name big/stuff | grep aaarrghh | xargs -n1 zfs destroy
</code></pre></div></div>
<p>It will delete all snapshots with the word ‘aaarrghh’ in its name from the file-system ‘big/stuff’.</p>Richard LaugesenDestroy ZFS snapshots matching a keywordMore wasps in Canberra2021-01-21T00:00:00+00:002021-01-21T00:00:00+00:00http://richardlaugesen.com/more-wasps<p><img src="/images/marvel-wasp.png" alt="Wasp by Marvel" /></p>
<p>We recently moved to a new suburb in Canberra and a wasp nest has sprung up in the courtyard.</p>
<p>Based on my <a href="/four-wasp-nests/">last experience with wasps</a> I was worried!</p>
<p>After a bit of research it turns out they are from <a href="https://en.wikipedia.org/wiki/Mud_dauber">mud dauber wasps</a> and nothing to be afraid of. They are solitary rather than social and the mum helps out in the garden by catching and feeding spiders and catalipilers to her babies. They are common in the Australian bush and stings only happen if they feel threatened.</p>
<p>Our new place is closer to the bush so perhaps that has something to do with getting these friendly wasps.</p>Richard LaugesenThey are solitary rather than social and the mum helps out in the garden by catching and feeding spiders and catalipilers to her babies.Canberra is first to see Cassini crash into Saturn2017-09-13T00:00:00+00:002017-09-13T00:00:00+00:00http://richardlaugesen.com/canberra-first-to-see-cassini-crash-into-saturn<p><img src="/images/cassini-breakup.jpg" alt="Artist’s impression of Cassini burning up in Saturn’s upper atmosphere. Credit: NASA/JPL-CALTECH" /></p>
<p>The <a href="https://en.wikipedia.org/wiki/Canberra_Deep_Space_Communication_Complex">Canberra Deep Space Communication Complex</a> will be the first place on Earth to receive the data from <a href="https://en.wikipedia.org/wiki/Cassini%E2%80%93Huygens">Cassini</a> as it crashes into Saturn in a few days. We live half an hour away, and so my 5 year old daughter and I are very excited!</p>
<p>But unfortunately it is closed.</p>
<p>So what to do? Here are a few links to track things online:</p>
<ul>
<li><a href="https://saturn.jpl.nasa.gov/mission/saturn-tour/where-is-cassini-now/">Latest Status</a></li>
<li><a href="https://www.youtube.com/watch?v=_5ZrSKpbdSg">Final view video</a></li>
<li><a href="https://www.nasa.gov/nasalive">NASA Live</a></li>
<li><a href="https://saturn.jpl.nasa.gov/galleries/raw-images?order=earth_date+desc&per_page=50&page=0">Raw image feed</a></li>
<li><a href="https://eyes.nasa.gov/dsn/dsn.html">Deep Space Network</a></li>
<li><a href="https://twitter.com/CassiniSaturn">Cassini Twitter</a></li>
<li><a href="https://twitter.com/CanberraDSN">Canberra DSN Twitter</a></li>
<li><a href="https://twitter.com/search?q=%23CassiniAus&src=typd">#CassiniAus</a></li>
<li><a href="https://twitter.com/hashtag/GrandFinale?src=hash">#GrandFinale</a></li>
</ul>
<p>I remember when Cassini launched in 1997 and when Huygens landed on Titan in 2005. Space exploration is a long game but I love it. The technology is reliable and the science just mind blowing. It’s amazing considering the spacecraft was built over 20 years ago.</p>
<p>Update: <a href="http://ciclops.org/index/8615/We-Came-We-Saw-Its-Done?js=1">Final captians log</a> post from Carolyn Porco, the one and only Cassini Imaging Team Leader</p>Richard LaugesenWe live half an hour away, and so my 5 year old daughter and I are very excited!Kids with high temperatures2017-09-11T00:00:00+00:002017-09-11T00:00:00+00:00http://richardlaugesen.com/kids-with-high-temperatures<p>I will spare you the backstory but a recent visit to our family doctor resulted in a fantastic education.</p>
<p>Here is what we learnt:</p>
<ul>
<li>Paracetamol and Ibuprofen reduce internal body temperature through different mechanisms</li>
<li>Giving them at the same time is okay and a more effective way to reduce internal temperature than giving them separately</li>
<li>Current recommendation is to avoid trying to reduce internal temperature, aim for comfort</li>
<li>High core temperature does not cause seizures or brain damage</li>
<li>Ibuprofen should be fine with a Factor VIII level around 40, but not 14</li>
<li>It’s common for kids to get secondary bacterial infections after a viral infection but hard to diagnose</li>
<li><a href="https://en.wikipedia.org/wiki/Scarlet_fever">Scarlet Fever</a> is caused by an infection of <a href="https://en.wikipedia.org/wiki/Streptococcus_pyogenes">group A Streptoccoccus</a> and can kill a child in a few days if not treated, it was the leading cause of death in the early 20th Century</li>
<li>An effective treatment for a strep infection is the antibiotic <a href="https://en.wikipedia.org/wiki/Phenoxymethylpenicillin">Phenoxymethylpenicillin</a>, first used in 1948</li>
<li>Phenoxymethylpenicillin is a narrow-spectrum antibiotic and therefore does not disrupt gut-flora as much (less active on <a href="https://en.wikipedia.org/wiki/Gram-negative_bacteria">gram negative bacteria</a>)</li>
<li>Kids with unexplained knee pain should be taken seriously, it may be the only symptom of <a href="https://en.wikipedia.org/wiki/Meningitis">Meningitis</a></li>
</ul>
<p>Want to know what is terrifying? A 5 year old with a temperature approaching 40 degrees for a week.</p>
<p>I’m grateful we have a good family doctor.</p>
<p>Update: She is feeling much better on day 3 of antibiotics</p>Richard LaugesenHigh core body temperatures do not cause seizures or brain damageTwisted fire starter2017-06-12T00:00:00+00:002017-06-12T00:00:00+00:00http://richardlaugesen.com/twisted-fire-starter<p><img src="/images/the-roof-is-on-fire.jpg" alt="Burning timber, happy family" /></p>
<p>So embarrassing!</p>
<p>Tried to start four fires in the last month and only one has worked. Which makes me think that one was a fluke.</p>
<p>The girls are disappointed and expectations are high.</p>
<p>Turns out that the things you learnt in Scouts 30 years ago don’t stick around without practice.</p>
<p>Could it be because the ground was damp?</p>Richard LaugesenSo embarrassing!Somewhat successful software2017-06-10T00:00:00+00:002017-06-10T00:00:00+00:00http://richardlaugesen.com/somewhat-successful-software<p>I’ve written a few pieces of software and two of them have been somewhat successful, many many more have not.</p>
<p>I once wrote some software for myself to automagically create classroom seating charts based on student relationships.</p>
<p>Turned out a few other teachers also wanted to do this so I gave it a name (Termites) and sold a few 100 licences. I lost interest after a few years and closed down the business but it was fun and profitable for a while.</p>
<p>I also wrote a testing platform for schools and universities with <a href="http://www.newcastle.edu.au/profile/mitch-otoole">Mitch O’Toole</a> called <a href="https://app.thinkliteracy.com/">Think Literacy</a>.</p>
<p>It has long since outgrown it’s name though and is now used for numeracy tests, cloze tests, corporate staff competency, and general multiple choice tests. With all those optionally linked with surveys to uncover relationships.</p>
<p>It has been used in 22 institutions by around 13,000 students.</p>Richard Laugesentwo of them have been somewhat successful, many many more have notOpenBSD for the desktop2017-04-15T00:00:00+00:002017-04-15T00:00:00+00:00http://richardlaugesen.com/openbsd-for-the-desktop<p><a href="http://www.openbsd.org/61.html">OpenBSD v6.1</a> was released a few days ago and I got curious - could it be used as an everyday desktop environment?</p>
<p><img src="/images/openbsd-banner1.gif" alt="Gotta love the OpenBSD art! Copyright [Theo de Raadt](http://www.openbsd.org/art1.html)" /></p>
<p>The install was much better than last time I tried (v5?). Got it to the point of a running Gnome, Firefox, and Emacs fairly quickly. This surprised me because it has been a really long time since I used any BSD and I’m now a complete beginner. It was very similar to Linux however and felt sufficiently familiar.</p>
<p>I used it for a few days as my primary desktop environment. The UI seemed a bit laggy but I’m guessing that was because I was running it in a virtual machine. And in general the experience felt a bit crippled and awkward compared to my Fedora desktop. I guess this is just because I don’t understand it and maybe those feelings would vanish with a bit of experience. The man pages and built in documentation are outstanding. And the small amount of code I looked at was very clean.</p>
<p>A common argument in favor of OpenBSD is that it is super secure.</p>
<p>I don’t entirely agree with that for a desktop environment.</p>
<p>I’m using the same user-space applications in both OpenBSD and Fedora and any security flaws in those applications are likely to be patched quicker in Fedora. Those applications are surely the majority of my attack surface. Therefore having a more secure operating system to run these applications on becomes less important. Perhaps I’m missing something?</p>
<p>OpenBSD is also missing a few things which I use pretty regularly - Anaconda Python, CUDA, and Mathematica.</p>
<p>And the applications which are available are a couple of versions behind what I have on Fedora. Which adds a potential security risk.</p>
<p>This <a href="https://allthatiswrong.wordpress.com/2010/01/20/the-insecurity-of-openbsd/">article</a> has a similar argument around security, and also has a pretty nasty comment thread.</p>
<p>If we drop the argument that OpenBSD is more secure, then what are the other benefits one gets from using it?</p>
<p>I really want to love <a href="http://www.openbsd.org/index.html">OpenBSD</a>, maybe I’m just missing something.</p>Richard LaugesenCould it be used as an everyday desktop environment?Four wasp nests2017-04-07T00:00:00+00:002017-04-07T00:00:00+00:00http://richardlaugesen.com/four-wasp-nests<p>We have four nests under the eves of our porch (in Canberra) and they all belong to native Australian wasps.</p>
<p>This shouldn’t be a problem unless it is in a high traffic area, which these are. I was stung once, it hurt!</p>
<p>They are a gardeners friend because they keep caterpillars under control.</p>
<p>The best advice is to remove them is to use a fast knock down insecticide spray after dusk when all adults are back on the nest. Just make sure there is a clear path back to the house so you don’t trip. Decided it would be a bit tricky to do this with four nests. I may succeed at killing the wasps on one nest but the wasps on the other three will probably start attacking me!</p>
<p>One is a nest of Roplalidia Plebeiana and the other three nests are Polistes Humilis. Names like that make the wasps sound very clever.</p>
<p><img src="/images/wasps-roplalidia-plebeina.jpeg" alt="Roplalidia Plebeiana wasp nest" />
<img src="/images/wasps-polistes-humilis-1.jpeg" alt="Polistes Humilis wasp nest" />
<img src="/images/wasps-polistes-humilis-2.jpeg" alt="Polistes Humilis wasp nest" /></p>
<p>I found this <a href="http://www.xcsconsulting.com.au/pdf/Paper_Wasps_of_Canberra.pdf">PDF article</a> really useful for identifying the species.</p>
<p>There’s a wasp hotline to call in Canberra on 0261621914. I think they will remove any European Wasps nests free of charge, and give free advice on other species of wasp but not removing the nests.</p>
<p><strong>Update</strong>: All wasps were gone by the second week of May, and the nests became a great preschool show-and-tell activity.</p>
<p><strong>Update</strong>: It’s early October and the wasps are back, exact same locations as last year.</p>
<p><strong>Update</strong>: Three <a href="https://en.wikipedia.org/wiki/Currawong">currawong</a> knocked the nest down and ate all the wasps at 7am on 27th March 2018. It was unusually cold, around 1°C.</p>Richard LaugesenAll wasps were gone by the second week of May, and the nests became a great preschool show-and-tell activity.Securing archives with encryption2016-12-30T00:00:00+00:002016-12-30T00:00:00+00:00http://richardlaugesen.com/securing-acrhives-with-encryption<p>I want to archive a directory and then encrypt it. And obviously get that directory back again sometime in future.</p>
<p>This will archive, compress, and encrypt:</p>
<div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>tar -cz some-directory | gpg -c -o archive.tgz.gpg
</code></pre></div></div>
<p>And this will decrypt, decompress, and extract:</p>
<div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>gpg -d archive.tgz.gpg | tar xz
</code></pre></div></div>
<p>This uses <a href="https://en.wikipedia.org/wiki/Symmetric-key_algorithm">symmetric encryption</a> with an <a href="https://en.wikipedia.org/wiki/Advanced_Encryption_Standard">AES128</a> cipher. AES128 is sufficient to protect classified information up to the SECRET level. Good enough for me.</p>Richard LaugesenSecurely archive a directory of filesTell me about yourself2016-12-18T00:00:00+00:002016-12-18T00:00:00+00:00http://richardlaugesen.com/tell-me-about-yourself<p><img src="/images/dilbert-job-interview.jpg" alt="Illustration by [Scott Adams](http://dilbert.com)" /></p>
<p>For those about to interview, answering that opening question can be tough.</p>
<p>Here is a simple approach to handle it that should only take about 1 minute.</p>
<p>Just tell them:</p>
<ul>
<li>Stuff you did in the past that matches what they want in the future</li>
<li>And a story that demonstrates one of your good qualities</li>
</ul>
<p>Don’t tell them:</p>
<ul>
<li>Your life story</li>
<li>Anything about pets, travel, or hobbies</li>
</ul>
<p>Writing it down first and practicing till it sounds natural is probably a good idea too.</p>Richard LaugesenSimple approach to handle that terrifying interview question