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I encountered the following error, when I wanted to connect to Oracle v12.2.0.1.0 database with Java 1.8.0_192-b26: java.sql.SQLRecoverableException: IO Error: Connection reset by peer, Authentication lapse 321631 ms. This was unexpected as the same program did run absolutely fine on another Linux…
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I had to provide access to an Oracle database but the standard port at 1521 was hindered by company firewall and company proxy rules. In previous times there was iSQL*Plus, but this product no longer seems to be available. I found Adminer as an alternative. It is written by Jakub Vrána. It is very…
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This blog was viewed more than 80.200 times since its inception and had more than 60.000 visitors. The averages per month are: Between 1,000 and 2,000 views per month in bar chart form: The most popular posts over all years are: The most popular blog posts this year were: USA is at the top of…
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In Using Odroid as IP Router I wrote about using my Odroid as router and firewall. Additionally I inspect who tries to log-in to my machines using the lastb command. Sample output is below: $ lastb admin ssh:notty 202.166.220.10 Mon Oct 1 09:51 - 09:51 (00:00) admin ssh:notty …
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Java Nashorn is the JavaScript engine shipped since Java 8. You can therefore use JavaScript wherever you have at least Java 8. Java 8 also has a standalone interpreter, called jjs. It is possible to create a Java HashMap and use this structure directly in JavaScript. Here is the code: import…
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This blog was viewed more than 71.400 times since its inception and had more than 54.000 visitors. The averages per month are: Between 1,000 and 2,000 views per month in bar chart form: The most popular blog posts over all years are: The most popular blog posts this year were:
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Had an issue with update of ARM ArchLinux which I use here. Error messages like: (95/95) checking keys in keyring [####################################################] 100% (95/95) checking package integrity …
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Beyond Compare is a graphical file comparison tool sold by Scooter Software. Its open-source competitors are mainly vimdiff, and kdiff3. Its advantage is ease-of-use. While comparing files they can be edited instantly. You can diff complete directory trees. It is written in Delphi Object Pascal,…
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One can use the instant messaging client Pidgin and Skype. Skype for Business was previously called Lync. Install Pidgin pacman -S pidgin and install the SIP/Simple protocol for Skype for Business/Office 365/Lync pacman -S pidgin-sipe Setting up the account: Use your company mail-address.…
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1. Problem statement. You have an encrypted disk and want to decrypt the disk during boot while not sitting in front of your computer. Solution is sketched and indicated in dm-crypt/Specialties. Below is a little bit more explanation. For the following you must be root. 2. Required software…
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Google announced that starting with Chrome version 68 they will gradually mark HTTP-connections as "not secure". "Let's Encrypt" is a free service for web-masters to obtain certificates in an easy manner. Work on "Let's Encrypt" started in 2014. Setting up "Let's…
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I stumbled upon Hiawatha web-server when I read about a web-server for a houseboat by Ronald Scheckelhoff, WB8LZR. I had used Apache, thttpd, Lighttp, NGINX, and others before. Now I use Hiawatha web-server. Hiawatha has three objectives, which are nicely met: Security: Hiawatha resisted…
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Very interesting article. Some remarkable excerpts: To isolate performance issues to the JavaScript VM, the authors rebuilt the client side of WebRsync using the Chrome native client support and C++. It’s much faster. Replacing MD5 with SipHash reduces computation complexity by almost 5x. As a…
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One lesser known Unix command is comm. This command is far less known than diff. comm needs two already sorted files FILE1 and FILE2. With the options -1 suppress column 1 (lines unique to FILE1) -2 suppress column 2 (lines unique to FILE2) -3 suppress column 3 (lines that appear in both…
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I wondered why Unix sort behaved strangely. printf "A0 1\nA 1\n" | sort delivered A0 1 A 1 Of course, I expected A to come before A0. This was strange, as printf "A1 1\nA 1\n" | sort produced A 1 A1 1 just as expected. Also, printf "A0\nA\n" | sort orders A…
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In the post Rewriting Perl to plain C the runtime of the serial runs were reported. As expected the C program was a lot faster than the Perl script. Now running programs in parallel showed two unexpected behaviours: (1) more parallelizations can degrade runtime, and (2) running unoptimized programs…
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Perl script was running too slow. Rewriting it in C made it 20 times faster. 1. Problem statement. Analyze call-tree dependency in COBOL programs. There are 77 million lines of COBOL code in ca. 30,000 files. These 30,000 COBOL programs could potentially include 74,000 COPY-books comprising 10…
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Many scripting languages, like Awk, Perl, Python, Lua, and so on, have hash-tables already built-in. I needed hashing functionality similar to Perl's hash-variables. In particular I needed lookup, insert, and iterating over all entries. I wrote on hashing in Hashing Just Random Numbers and Hash…
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On 23-Oct-2017 Filippo Mantovani held a talk in Darmstadt on "Mobile technology for production-ready high-performance computing systems: The path of the Mont-Blanc project". Unfortunately I was unable to attend, but Mr. Mantovani sent me his Darmstadt Seminar slides. As his slides and…
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1. Prerequisites Assume one owns $n>0$ different products, $n\in\mathbb{N}$, usually $n\approx 100$. Each product has a cost $c_i>0$, $c_i\in\mathbb{R}$, associated with this ownership, $i=1,\ldots, n$. Let $N=\left\{1,\ldots,n\right\}$, and $\mathbb{P}(N)$ be the powerset of $N$, i.e., the…