etbe - Russell Coker

Quarantine Will normalise WFH and Recession will Denormalise Jobs [3]. I guess we can always hope that after a disaster we can learn to do things better than before.

Tyre wear is worse than exhaust for small particulate matter [4]. We need better tyres and legal controls over such things.

Scott Santens wrote an insightful article about the need for democracy and unconditional basic income [5]. “In ancient Greece, work was regarded as a curse” is an extreme position but strongly supported by evidence. ‘In his essay “In Praise of Idleness,” Bertrand Russell wrote “Modern methods of production have given us the possibility of ease and security for all; we have chosen, instead, to have overwork for some and starvation for others. Hitherto we have continued to be as energetic as we were before there were machines; in this we have been foolish, but there is no reason to go on being foolish forever.”‘

Cory Doctorow wrote an insightful article for Locus titled A Lever Without a Fulcrum Is Just a Stick about expansions to copyright laws [6]. One of his analogies is that giving a bullied kid more lunch money just allows the bullies to steal more money, with artists being bullied kids and lunch money being the rights that are granted under copyright law. The proposed solution includes changes to labor and contract law, presumably Cory will write other articles in future giving the details of his ideas in this regard.

The Register has an amusing article about the trial of a former CIA employee on trial for being the alleged “vault 7 leaker” [7]. Both the prosecution and the defence are building their cases around the defendent being a jerk. The article exposes poor security and poor hiring practices in the CIA.

CNN has an informative article about Finland’s war on fake news [8]. As Finland has long standing disputes with Russia they have had more practice at dealing with fake news than most countries.

The Times of Israel has an interesting article about how the UK used German Jews to spy on German prisoners of war [9].

Cory Doctorow wrote an insightful article “Data is the New Toxic Waste” about how collecting personal data isn’t an asset, it’s a liability [10].

Ulrike Uhlig wrote an insightful article about “Control Freaks”, analysing the different meanings of control, both positive and negative [11].

538 has an informative article about the value of statistical life [12]. It’s about $9M per person in the US, which means a mind-boggling amount of money should be spent to save the millions of lives that will be potentially lost in a natural disaster (like Coronavirus).

NPR has an interesting interview about Crypto AG, the Swiss crypto company owned by the CIA [13]. I first learned of this years ago, it’s not new, but I still learned a lot from this interview.

Coronavirus and Work

Currently the big news issue is all about how to respond to Coronavirus. The summary of the medical situation is that it’s going to spread exponentially (as diseases do) and that it has a period of up to 6 days of someone being infectious without having symptoms. So you can get a lot of infected people in an area without anyone knowing about it. Therefore preventative action needs to be taken before there’s widespread known infection.

Governments seem disinterested in doing anything about the disease before they have proof of widespread infection. They won’t do anything until it’s too late.

I finished my last 9-5 job late last year and hadn’t got a new one since then. Now I’m thinking of just not taking any work that requires much time spend outside home. If you don’t go to a workplace there isn’t a lot you have to do that involves leaving home.

Shopping is one requirement for leaving home, but the two major supermarket chains in my area (Coles and Woolworths) both offer home delivery for a small price so that covers most shopping. Getting groceries delivered means that they will usually come from the store room not the shop floor so wouldn’t have anyone coughing or sneezing on them. If you are really paranoid (which I aren’t at the moment) then you could wear rubber gloves to bring the delivery in and then wash everything before using it. It seems that many people have similar ideas to me, normally Woolworths allows booking next-day delivery, now you have to book at least 5 days (3 business days) in advance.

If anyone needs some Linux work done from remote then let me know. Otherwise I’ll probably spend the next couple of months at home doing Debian coding and watching documentaries on Netflix.

Amazon Prime and Netflix

I’ve been trying both Amazon Prime and Netflix. I signed up for the month free of Amazon Prime to watch “Good Omens” and “Picard”. “Good Omens” is definitely worth the effort of setting up the month free of Amazon Prime and is worth the month’s subscription if you have used your free month in the past and Picard is ok.

Content

Amazon Prime has a medium amount of other content, I’m now paying for a month of Amazon Prime mainly because there’s enough documentaries to take a month. For reference there are plenty of good ones about war and about space exploration. There are also some really rubbish documentaries, for example a 2 part documentary about the Magna Carta where the second part starts with Grover Norquist claiming that the Magna Carta is justification for not having any taxes (the first part seemed ok).

Netflix has a lot of great content. A big problem with Netflix is that there aren’t good ways of searching and organising the content you want to watch. It would be really nice if Netflix could use some machine learning for recommendations and recommend shows based on what I’ve liked and also what I’ve disliked.

On both Netflix and Amazon when you view the details of a show it gives a short list of similar shows which is nice. With Amazon I have no complaints about that. But with Netflix the content library is so great that you get lost in a maze of links. On the Android tablet interface for Netflix it shows 12 similar shows in a grid and on the web interface it’s a row of 20 shows with looped scrolling. Then as you click a different show you get another list of 12/20 shows which will usually have some overlap with the previous one. It would be nice if you could easily swipe left on shows you don’t like to avoid having them repeatedly presented to you.

On Netflix I’ve really enjoyed the “Altered Carbon” series (which is significantly more violent than I anticipated), “Black Mirror” (the episode written by Trent Reznor and starring Miley Cyrus is particularly good), and “Love Death and Robots”. Overall I currently rate “Love Death and Robots” as in many ways the best series I’ve ever watched because the episodes are all short and get straight to the point. One advantage of online video is that they don’t need to pad episodes out or cut them short to fit a TV time slot, they can use as much time as necessary to tell the story.

Watch List

Having a single row of shows to watch is fine for the amount of content that Amazon has, but for the Netflix content you can easily get 100 shows on your watch list and it would be good to be able to search my watch list by genre (it’s a drag to flick through dozens of icons of war documentaries when I’m in the mood for an action movie as the icons are somewhat similar).

As well as a list of shows you selected to watch Netflix has a list of shows that have been recently watched with no way to edit it which is separate from the list of shows selected to watch. So if you watch 5 minutes of a show and decide that it sucks then it stays on the list until you have partially watched 10 other shows recently. For my usage the recently watched list is the most important thing as I’m watching some serial shows and wouldn’t want to go through the 100 shows on my watch list to find them. If I’ve decided that a movie sucked after watching a bit of it I don’t want to be reminded of it by seeing the icon every time I use Netflix for the next month.

Amazon has only a single “watch next” list for shows that you have watched recently and shows that you selected as worth watching. It allows editing the list which is nice, but then Amazon also often keeps shows on the list when you have finished watching them and removed them from the “to watch” setting. Amazon’s watch list is also generally buggy, at one time it decided that a movie was no longer available in my region but didn’t let me remove it from the list.

Quality

Apparently the Netflix web interface on Linux only allows 720p video while the Amazon web interface on all platforms is limited to 720p. In any case my Internet connection is probably only good enough for 1080p at most. I haven’t noticed any quality differences between Netflix and Amazon Prime.

Multiple Users

Netflix allows you to create profiles for multiple users with separate watch lists which is very handy. They also don’t have IP address restrictions so it’s a common practice for people to share a Netflix account with relatives. If you try to use Netflix when the maximum number of sessions for your account is in use it will show a list of what the other people on your account are watching (so if you share with your parents be careful about that).

Amazon doesn’t allow creating multiple profiles, but the content isn’t that great. The trend in video streaming is for proprietary content to force users to subscribe to a service. So sharing an Amazon Prime account with a few people so you want watch the proprietary content would make sense.

Watching Patterns

Sometimes when I’m particularly distracted I can’t focus on one show for any length of time. Both Amazon and Netflix (and probably all other online streaming services) allow me to skip between shows easily. That’s always been a feature of YouTube, but with YouTube you get recommended increasingly viral content until you find yourself watching utter rubbish. At least with Amazon and Netflix there is a minimum quality level even if that is reality TV.

Conclusion

Amazon Prime has a smaller range of content and some really rubbish documentaries. I don’t mind the documentaries about UFOs and other fringe stuff as it’s obvious what it is and you can avoid it. A documentary that has me watching for an hour before it’s revealed to be a promo for Grover Norquist is really bad, did the hour of it that I watched have good content or just rubbish too?

Netflix has a huge range of content and the quality level is generally very high.

If you are going to watch TV then subscribing to Netflix is probably a good idea. It’s reasonably cheap, has a good (not great) interface, and has a lot of content including some great original content.

For Amazon maybe subscribe for 1 month every second year to binge watch the Amazon proprietary content that interests you.

Links February 2020

Truthout has an interesting summary of the US “Wars Without Victory and Weapons Without End” [1]. The Korean war seems mostly a win for the US though.

The Golden Age of White Collar Crime is an informative article about the epidemic of rich criminals in the US that are protected at the highest levels [2]. This disproves the claims about gun ownership preventing crime. AFAIK no-one has shot a corporate criminal in spite of so many deserving it.

Law and Political Economy has an insightful article “Privatizing Sovereignty, Socializing Property: What Economics Doesnâ€™t Teach You About the Corporation” [3]. It makes sense of the corporation law system.

IDR labs has a communism test, I scored 56% [4].

Vice has an interesting article about companies providing free email programs and services and then selling private data [5]. The California Consumer Privacy Act is apparently helping as companies that do business in the US can’t be sure which customers are in CA and need to comply to it for all users. Don’t trust corporations with your private data.

The Atlantic has an interesting article about Coronavirus and the Blindness of Authoritarianism [6]. The usual problem of authoritarianism but with a specific example from China. The US is only just astarting it’s experiment with authoritarianism and they are making the same mistakes.

The Atlantic has an insightful article about Coronavirus and it’s effect on China’s leadership [7]. It won’t change things much.

On The Commons has an insightful article We Now Have a Justice System Just for Corporations [8]. In the US corporations can force people into arbitration for most legal disputes, as they pay the arbitration companies the arbitration almost always gives the company the result they pay for.

Boing Boing has an interesting article about conspiracy theories [9]. Their point is that some people have conspiracy theories (meaning belief in conspiracies that is not based in fact) due to having seen real conspiracies at close range. I think this only applies to a minority of people who believe conspiracy theories, and probably only to people who believe in a very small number of conspiracies. It seems that most people who believe in conspiracy theories believe in many of them.

Douglas Rushkoff wrote a good article about rich people who are making plans to escape after they destroy the environment [10]. Includes the idea of having shock-collars for security guards to stop them going rogue.

Boing Boing has an interesting article on the Brahmin Left and the Merchant Right [11]. It has some good points about the left side of politics representing the middle class more than the working class, especially the major left wing parties that are more centrist nowadays (like Democrats in the US and Labor in Australia).

[1] http://tinyurl.com/rpu7ol8
[2] https://www.huffpost.com/highline/article/white-collar-crime/
[3] http://tinyurl.com/tv473gk
[4] https://www.idrlabs.com/communism/test.php
[5] http://tinyurl.com/vn53f4t
[6] http://tinyurl.com/rqpn7oa
[7] http://tinyurl.com/swenoz3
[8] http://tinyurl.com/v5xtpvl
[9] http://tinyurl.com/y3m68qgk
[10] http://tinyurl.com/y395lzwd
[11] http://tinyurl.com/y4tpy7u5

DisplayPort and 4K

The Problem

Video playback looks better with a higher scan rate. A lot of content that was designed for TV (EG almost all historical documentaries) is going to be 25Hz interlaced (UK and Australia) or 30Hz interlaced (US). If you view that on a low refresh rate progressive scan display (EG a modern display at 30Hz) then my observation is that it looks a bit strange. Things that move seem to jump a bit and it’s distracting.

Getting HDMI to work with 4K resolution at a refresh rate higher than 30Hz seems difficult.

What HDMI Can Do

According to the HDMI Wikipedia page [1], HDMI 1.3 (introduced in June 2006) to 1.4b (introduced in October 2011) supports 30Hz refresh at 4K resolution and if you use 4:2:0 Chroma Subsampling (see the Chroma Subsampling Wikipedia page [2] you can do 60Hz or 75Hz on HDMI 1.3 to 1.4b. Basically for colour 4:2:0 means half the horizontal and half the vertical resolution while giving the same resolution for monochrome. For video that apparently works well (4:2:0 is standard for Blue Ray) and for games it might be OK, but for text (my primary use of computers) it would suck.

So I need support for HDMI 2.0 (introduced in September 2013) on the video card and monitor to do 4K at 60Hz. Apparently none of the combinations of video card and HDMI cable I use for Linux support that.

HDMI Cables

The Wikipedia page alleges that you need either a “Premium High Speed HDMI Cable” or a “Ultra High Speed HDMI Cable” for 4K resolution at 60Hz refresh rate. My problems probably aren’t related to the cable as my testing has shown that a cheap “High Speed HDMI Cable” can work at 60Hz with 4K resolution with the right combination of video card, monitor, and drivers. A Windows 10 system I maintain has a Samsung 4K monitor and a NVidia GT630 video card running 4K resolution at 60Hz (according to Windows). The NVidia GT630 card is one that I tried on two Linux systems at 4K resolution and causes random system crashes on both, it seems like a nice card for Windows but not for Linux.

Apparently the HDMI devices test the cable quality and use whatever speed seems to work (the cable isn’t identified to the devices). The prices at a local store are $3.98 for “high speed”, $19.88 for “premium high speed”, and $39.78 for “ultra high speed”. It seems that trying a “high speed” cable first before buying an expensive cable would make sense, especially for short cables which are likely to be less susceptible to noise.

What DisplayPort Can Do

According to the DisplayPort Wikipedia page [3] versions 1.2â€“1.2a (introduced in January 2010) support HBR2 which on a “Standard DisplayPort Cable” (which probably means almost all DisplayPort cables that are in use nowadays) allows 60Hz and 75Hz 4K resolution.

Comparing HDMI and DisplayPort

In summary to get 4K at 60Hz you need 2010 era DisplayPort or 2013 era HDMI. Apparently some video cards that I currently run for 4K (which were all bought new within the last 2 years) are somewhere between a 2010 and 2013 level of technology.

Also my testing (and reading review sites) shows that it’s common for video cards sold in the last 5 years or so to not support HDMI resolutions above FullHD, that means they would be HDMI version 1.1 at the greatest. HDMI 1.2 was introduced in August 2005 and supports 1440p at 30Hz. PCIe was introduced in 2003 so there really shouldn’t be many PCIe video cards that don’t support HDMI 1.2. I have about 8 different PCIe video cards in my spare parts pile that don’t support HDMI resolutions higher than FullHD so it seems that such a limitation is common.

The End Result

For my own workstation I plugged a DisplayPort cable between the monitor and video card and a Linux window appeared (from KDE I think) offering me some choices about what to do, I chose to switch to the “new monitor” on DisplayPort and that defaulted to 60Hz. After that change TV shows on NetFlix and Amazon Prime both look better. So it’s a good result.

As an aside DisplayPort cables are easier to scrounge as the HDMI cables get taken by non-computer people for use with their TV.

Self Assessment

Background Knowledge

The Dunning Kruger Effect [1] is something everyone should read about. It’s the effect where people who are bad at something rate themselves higher than they deserve because their inability to notice their own mistakes prevents improvement, while people who are good at something rate themselves lower than they deserve because noticing all their mistakes is what allows them to improve.

Noticing all your mistakes all the time isn’t great (see Impostor Syndrome [2] for where this leads).

Erik Dietrich wrote an insightful article “How Developers Stop Learning: Rise of the Expert Beginner” [3] which I recommend that everyone reads. It is about how some people get stuck at a medium level of proficiency and find it impossible to unlearn bad practices which prevent them from achieving higher levels of skill.

What I’m Concerned About

A significant problem in large parts of the computer industry is that it’s not easy to compare various skills. In the sport of bowling (which Erik uses as an example) it’s easy to compare your score against people anywhere in the world, if you score 250 and people in another city score 280 then they are more skilled than you. If I design an IT project that’s 2 months late on delivery and someone else designs a project that’s only 1 month late are they more skilled than me? That isn’t enough information to know. I’m using the number of months late as an arbitrary metric of assessing projects, IT projects tend to run late and while delivery time might not be the best metric it’s something that can be measured (note that I am slightly joking about measuring IT projects by how late they are).

If the last project I personally controlled was 2 months late and I’m about to finish a project 1 month late does that mean I’ve increased my skills? I probably can’t assess this accurately as there are so many variables. The Impostor Syndrome factor might lead me to think that the second project was easier, or I might get egotistical and think I’m really great, or maybe both at the same time.

This is one of many resources recommending timely feedback for education [4], it says “Feedback needs to be timely” and “It needs to be given while there is still time for the learners to act on it and to monitor and adjust their own learning”. For basic programming tasks such as debugging a crashing program the feedback is reasonably quick. For longer term tasks like assessing whether the choice of technologies for a project was good the feedback cycle is almost impossibly long. If I used product A for a year long project does it seem easier than product B because it is easier or because I’ve just got used to it’s quirks? Did I make a mistake at the start of a year long project and if so do I remember why I made that choice I now regret?

Skills that Should be Easy to Compare

One would imagine that martial arts is a field where people have very realistic understanding of their own skills, a few minutes of contest in a ring, octagon, or dojo should show how your skills compare to others. But a YouTube search for “no touch knockout” or “chi” shows that there are more than a few “martial artists” who think that they can knock someone out without physical contact – with just telepathy or something. George Dillman [5] is one example of someone who had some real fighting skills until he convinced himself that he could use mental powers to knock people out. From watching YouTube videos it appears that such people convince the members of their dojo of their powers, and those people then faint on demand “proving” their mental powers.

The process of converting an entire dojo into believers in chi seems similar to the process of converting a software development team into “expert beginners”, except that martial art skills should be much easier to assess.

Is it ever possible to assess any skills if people trying to compare martial art skills often do it so badly?

Conclusion

It seems that any situation where one person is the undisputed expert has a risk of the “chi” problem if the expert doesn’t regularly meet peers to learn new techniques. If someone like George Dillman or one of the “expert beginners” that Erik Dietrich refers to was to regularly meet other people with similar skills and accept feedback from them they would be much less likely to become a “chi” master or “expert beginner”. For the computer industry meetup.com seems the best solution to this, whatever your IT skills are you can find a meetup where you can meet people with more skills than you in some area.

Here’s one of many guides to overcoming Imposter Syndrome [5]. Actually succeeding in following the advice of such web pages is not going to be easy.

I wonder if getting a realistic appraisal of your own skills is even generally useful. Maybe the best thing is to just recognise enough things that you are doing wrong to be able to improve and to recognise enough things that you do well to have the confidence to do things without hesitation.

Deleted Mapped Files

On a Linux system if you upgrade a shared object that is in use any programs that have it mapped will list it as “(deleted)” in the /proc/PID/maps file for the process in question. When you have a system tracking the stable branch of a distribution it’s expected that most times a shared object is upgraded it will be due to a security issue. When that happens the reasonable options are to either restart all programs that use the shared object or to compare the attack surface of such programs to the nature of the security issue. In most cases restarting all programs that use the shared object is by far the easiest and least inconvenient option.

Generally shared objects are used a lot in a typical Linux system, this can be good for performance (more cache efficiency and less RAM use) and is also good for security as buggy code can be replaced for the entire system by replacing a single shared object. Sometimes it’s obvious which processes will be using a shared object (EG your web server using a PHP shared object) but other times many processes that you don’t expect will use it.

I recently wrote “deleted-mapped.monitor” for my etbemon project [1]. This checks for shared objects that are mapped and deleted and gives separate warning messages for root and non-root processes. If you have the unattended-upgrades package installed then your system can install security updates without your interaction and then the monitoring system will inform you if things need to be restarted.

The Debian package debian-goodies has a program checkrestart that will tell you what commands to use to restart daemons that have deleted shared objects mapped.

Now to solve the problem of security updates on a Debian system you can use unattended-upgrades to apply updates, deleted-mapped.monitor in etbemon to inform you that programs need to be restarted, and checkrestart to tell you the commands you need to run to restart the daemons in question.

If anyone writes a blog post about how to do this on a non-Debian system please put the URL in a comment.

While writing the deleted-mapped.monitor I learned about the following common uses of deleted mapped files:

/memfd: is for memfd https://dvdhrm.wordpress.com/tag/memfd/ [2]
/[aio] is for asynchronous IO I guess, haven’t found good docs on it yet.
/home is used for a lot of harmless mapping and deleting.
/run/user is used for systemd dconf stuff.
/dev/zero is different for each map and thus looks deleted.
/tmp/ is used by Python (and probably other programs) creates temporary files there for mapping.
/var/lib is used for lots of temporary files.
/i915 is used by some X apps on systems with Intel video, I don’t know why.

Social Media Sharing on Blogs

My last post was read directly (as opposed to reading through Planet feeds) a lot more than usual due to someone sharing it on lobste.rs. Presumably the people who read it that way benefited from reading it and I got a couple of unusually insightful comments from people who don’t usually comment on my blog. The lobste.rs sharing was a win for everyone.

There are a variety of plugins for social media sharing, most of which allow organisations like Facebook to track people who read your blog which is why I haven’t been using them.

Are there good ways of allowing people to easily share your blog posts which work in a reasonable way by not allowing much tracking of users unless they actually want to share content?

Load Average Monitoring

For my ETBE-Mon [1] monitoring system I recently added a monitor for the Linux load average. The Unix load average isn’t a very good metric for monitoring system load, but it’s well known and easy to use. I’ve previously written about the Linux load average and how it’s apparently different from other Unix like OSs [2]. The monitor is still named loadavg but I’ve now made it also monitor on the usage of memory because excessive memory use and load average are often correlated.

For issues that might be transient it’s good to have a monitoring system give a reasonable amount of information about the problem so it can be diagnosed later on. So when the load average monitor gives an alert I have it display a list of D state processes (if any), a list of the top 10 processes using the most CPU time if they are using more than 5%, and a list of the top 10 processes using the most RAM if they are using more than 2% total virtual memory.

For documenting the output of the free(1) command (or /proc/meminfo when writing a program to do it) the best page I found was this StackExchange page [3]. So I compare MemAvailable+SwapFree to MemTotal+SwapTotal to determine the percentage of virtual memory used.

Any suggestions on how I could improve this?

The code is in the recent releases of etbemon, it’s in Debian/Unstable, on the project page on my site, and here’s a link to the loadave.monitor script in the Debian Salsa Git repository [4].

Links January 2020

C is Not a Low Level Language [1] is an insightful article about the problems with C and the overall design of most current CPUs.

Interesting article about how the Boeing 737Max failure started with a takeover by MBA aparatcheks [2].

Interesting article about the risk of blood clots in space [3]. Widespread human spaceflight is further away than most people expect.

Wired has an insightful article about why rich people are so mean [4]. Also some suggestions for making them less mean.

Google published interesting information about their Titan security processor [5]. It’s currently used on the motherboards of GCP servers and internal Google servers. It would be nice if Google sold motherboards with a version of this.

Interesting research on how the alleged Supermicro motherboard backdoor [6]. It shows that while we may never know if the alleged attack took place such things are proven to be possible. In security we should assume that every attack that is possible is carried out on occasion. It might not have happen when people claim it happened, but it probably happened to someone somewhere. Also we know that TAO carried out similar attacks.

Arstechnica has an interesting article about cracking old passwords used by Unix pioneers [7]. In the old days encrypted passwords weren’t treated as secrets (/etc/passwd is world readable and used to have the encrypted passwords) and some of the encrypted passwords were included in source archives and have now been cracked.

Jim Baker (former general counsel of the FBI) wrote an insightful article titled Rethinking Encryption [8]. Lots of interesting analysis of the issues related to privacy vs the ability of the government to track criminals.

The Atlantic has an interesting article The Coalition Out to Kill Tech as We Know It [9] about the attempts to crack down on the power of big tech companies. Seems like good news.

The General Counsel of the NSA wrote an article “I Work for N.S.A. We Cannot Afford to Lose the Digital Revolution” [10].

Thoughts and Prayers by Ken Liu is an insightful story about trolling and NRA types [11].

Cory Doctorow wrote an insightful Locus article about the lack of anti-trust enforcement in the tech industry and it’s free speech implications titles “Inaction is a Form of Action” [12].

etbe – Russell Coker

Archives

Categories

Links March 2020

Coronavirus and Work

Amazon Prime and Netflix

Content

Watch List

Quality

Multiple Users

Watching Patterns

Conclusion

Links February 2020

DisplayPort and 4K

The Problem

What HDMI Can Do

HDMI Cables

What DisplayPort Can Do

Comparing HDMI and DisplayPort

The End Result

Self Assessment

Background Knowledge

What I’m Concerned About

Skills that Should be Easy to Compare

Conclusion

Deleted Mapped Files

Social Media Sharing on Blogs

Load Average Monitoring

Links January 2020

Archives

Email and RSS

Archives

Categories

Tags

Content

Watch List

Quality

Multiple Users

Watching Patterns

Conclusion

The Problem

What HDMI Can Do

HDMI Cables

What DisplayPort Can Do

Comparing HDMI and DisplayPort

The End Result

Background Knowledge

What I’m Concerned About

Skills that Should be Easy to Compare

Conclusion

Archives

Email and RSS