My Site was down early this morning.

I use my computers at home to host my Web-site, including this blog. But the IP address I have at home, is just a regular, dynamically-assigned IP address, which is owned by my ISP. This IP address can be reassigned to be at any moment.

Therefore, I have an update service which makes my changed IP address available to people who may want to access my URLs.

This morning, this update service failed to do its job correctly. And therefore, my Site was unavailable from 4h40 until 6h50.

This problem has now been corrected in an easy way.

Dirk

 

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Switched In a Replacement Keyboard

This is a situation which brings back memories of my Late Father, who repatriated to Germany in the late 1990s and early 2000s. He had a habit of giving me gifts that included computers and computer accessories.

During a visit which I made to Germany in 2010, he gave me a laptop that he didn’t need anymore, and which is in fact the Acer Aspire 5020 I mentioned before.

Link to Previous Posting

But his gifts that year included a good laptop bag, and also a keyboard. What I found peculiar about Dad, was that it had seemed very important to him, to find a keyboard in Germany which emulated the standard 105-key, US keyboard layout. Evidently he had been away from Canada and the USA for so long, that he could not remember what the US keyboard layout was. And so specifically for me, he had purchased a new K.B., which had the U.K. layout. This is entirely logical, because of the geographic proximity Germany has to Great Britain.

But Dad seemed struck so sad, when he learned that the K.B. he had bought for me wasn’t really a US-layout board. I tried to explain to him, that a Linux computer can easily be switched from one keyboard layout to another, and that the only challenge we faced, was to identify which layout this keyboard had. Because, we had actually failed to find this out, for which reason I did not make immediate use of it.

And, we did not have the time to solve the puzzle either, because we had his laptop to set up, as well as numerous other things to do in Germany, while my Father was still alive.

But, Not knowing what the keyboard layout is, can do far more damage, than simply having a layout from a nearby country. But Dad felt it was the other way around.

The computer I name ‘Pheonix’ possessed a Hewlett-Packard keyboard which had always served me well. But now the time came to retire that old K.B., which was my occasion this evening to switch in the one which my Late Father had given to me in 2010.

This K.B. is of the brand-name “Cherry”, and just by Googling that, I found out that Cherry was a later generation, high-quality keyboard brand. I tend to appreciate keyboards that have good tactile properties, and high-quality switches. Even though Cherries are not genuine “Clickety Keyboards”, they come close. I expect that this one will last me a long time. It’s quite robust.

Dirk

 

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The Drop-Sensors on my Neato XV Vacuuming Robot

I initially had the false impression, that this vacuuming robot, a “Neato XV Signature”, only had three ways to sense its surroundings: The laser which turns in its turret, the pressure-bar in the front with its two switches, and the magnetic sensors in its front corners.

Neato XV _1

But as it happens, this robot also has two optical “drop-sensors” in front, which statically look straight down at the ground.

I think the main purpose of these drop-sensors, is just to allow it to travel in a straight line. With a robot traveling over real terrain, a simple command to its left and right wheels to turn with the same amount of power, is not sufficient. This robot uses the feedback of its front drop-sensors, to measure the speed of the floor passing underneath.

I was watching it today, as it was having problems for the first time to travel in a straight line. And when I intervened, its display told me to “Please Clean My Left Drop-Sensor.”

These sensors can get dusty easily, and need to be wiped from time to time. And the plastic in front of its base-station also needs to be wiped free of dust, so that the robot can find its base-station again when ‘returning home’.

I now think that some of the malfunctions other people have reported, may in fact have been due to some of these panels not having been cleaned.

Also, it was my initial expectation that this robot stored the location of the base-station, when leaving the closest room, to clean farther reaches of its assigned area. In reality, when returning to the base station, this robot needs to find it again each time. Behind the panel of the base-station, there must be some sort of infrared corner-cubes, which glitter especially brightly in response to the laser, for it to recognize. Well it can happen that we have other objects hanging at the right or wrong distance above the ground, such as a set of curtains, which look unremarkable to the naked eye, but which also glitter to the vision of the infrared laser. And this can result in the robot making a mistaken attempt, to try docking in a corner of the correct room, but in a place where the base-station is not. And so such sources of glitter must also be removed from the room of the base-station.

Dirk

 

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How I typically Solve my Kleopatra Start-Up Delay Problem

Both under Linux and under Windows, I use “Kleopatra”, which is a GUI for the ‘GnuPG’ system – the “GNU Privacy Guard”. In case the reader does not know, GnuPG or ‘GPG’ is one software alternative for providing ‘Public Key Cryptography’, which can be used in practice to sign and/or encrypt emails, as well as to validate digital signatures made by other people’s computers.

Using GPG does not strictly require that we use Kleopatra, because there exists the capability which some power-users have, to use GPG from the command-line, and Kleopatra is a distinctly KDE-based front-end, even though there exist Windows ports of it.

One problem which I eventually run in to, and which has been reported elsewhere on the Internet, is that at first after installation, Kleopatra seems to run fine, but that after some point in time we encounter a strange delay, when we start up this program, which can last for several minutes or even longer, during which the program does not respond properly to user commands. Our GPG installation does not seem to be compromised.

In my case, this seems to take place entirely, because Kleopatra has been instructed to check the revocation status of some certificates, but no ‘OCSP Server’ has been specified in its settings. According to some other reports on the Web, this is a problem specific to “CACert” certificates, and in my case also, the problem seems to set in, after I’ve added a CACert certificate to my key-ring. Yet, AFAIK, this problem could just as easily occur after we’ve added other certificates.

The way I eventually solve this problem – on every computer I own – is to open Kleopatra somehow, and then to go into Settings -> Configure Kleopatra -> S/MIME Validation , and then to look at the field which says “OCSP responder URL”. By default, this field will be blank.

Since in my case the problem starts after I’ve added my CACert certificate, I actually add the OCSP Server which is provided by CACert there, which is currently “http://ocsp.cacert.org/”. After that, I find that when I open Kleopatra, a narrow and subtle progress-bar in the lower right of the application window, sweeps to completion within one second, and the program opens fine.

I need to explain why this solution works for me, so that anybody who may be having the same problem, but not with a CACert certificate, can also solve this problem.

Certificates which are not self-signed, are signed by a ‘Certificate Authority’, such as CACert. When Kleopatra starts, one of the functions which it automatically performs is to check its certificates against a ‘Revocation List’, in case the Certificate Authority has decided to revoke it.

The actual certificate which I received from CACert, has the detail encoded into its plain-text data, that its revocation status must always be checked. But what I’ve found happens with Kleopatra specifically, is that if no OCSP Server has been specified, instead of somehow recognizing the fact that it cannot check the revocation status, this program goes into some type of infinite loop, never actually connecting to any server, but also never seeming to exit this state.

I choose to put this OCSP, because in my case, I know that it is the CACert certificate which has this need set with a high priority. It should be possible to put some other OCSP Server into the same field, because ultimately they should all be synchronized. But finally, the OCSP Server provided by the same Certificate Authority, also provides the fastest response time, for validating its own certificates.

As I see it, there was a problem in priorities somewhere, in programming this application. There was the bureaucratic priority, which states that the status of this certificate must always be checked. but then there was also the programming priority, which states that an attempt to connect to a server, without any specification of which server, will lead to some sort of malfunction eventually. And between these two, the bureaucratic priority won out.

There are some people on the Web who choose to solve this problem, by simply deactivating the feature, of online revocation checking. This can be done within the same settings tab, by unchecking the first check-box in that tab. This check-box is located directly before the setting, to “Check certificate validity every Hour” (on my setup, with a drop-down window set to “hour”). I prefer to let my software do everything it’s supposed to do, including to check the revocation status of my certificates. And the way to do the latter is to specify an OCSP Server. The fact that this problem can apparently be solved both ways, affirms the quality of the programming.

Dirk

 

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