Elmar Klausmeier @eklausmeier - Tumblr Blog

Moved Blog To eklausmeier.goip.de

This blog here is no longer maintained. I moved to https://eklausmeier.goip.de. During migration I corrected a couple of minor typos and dead links. Main reasons: This new editor put the last nail in the coffin, existing content is garbled once you edit itMath typesetting is quite arduous, would like to have full MathJax supportOverall slowImporting does not allow to overwrite…

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PHP extension seg-faulting

Task at hand: Call Cobol (=GnuCobol) from PHP. I used FFI for this: <?php $cbl = FFI::cdef("int phpsqrt(void); void cob_init_nomain(int,char**); int cob_tidy(void);", "/srv/http/phpsqrt.so"); $ffj0 = FFI::cdef("double j0(double);", "libm.so.6"); $cbl->cob_init_nomain(0,null); $ret = $cbl->phpsqrt(); printf("\tret = %d<br>\n",$ret); echo "Before calling cob_tidy():<br>\n"; echo "\tReturn: ",…

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Add Disjoint IP Addresses To SSHGuard Blacklist

Problem at hand: There are multiple machines running SSHGuard. Each of these machines accumulates different sets of blacklists. Task: Add disjoint IP addresses from one machine to another machine’s blacklist. 1. Copy from “master” machine: scp -p master:/var/db/sshguard/blacklist.db blacklist_master.db This blacklist looks like…

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#SSHGuard

Lesser Known Static Site Generators

Well known static site generators are Hugo (written in Go), Pelican (written in Python), Grav (written in PHP), or Eleventy (written in JavaScript). For a list of static site generators see Jamstack (322 generators listed) or Static Site Generators (460 generators listed). The following three static site generators unfortunately are not listed in before given Jamstack overview. mkws: a…

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#SSG

Testing J-Pilot feature-gtk3 branch

J-Pilot still relies on GTK+ 2, which is heading towards planned deprecation. The entire work to migrate to GTK+ 3 is done by volunteers, Judd Montgomery and David Malia. This post is about testing this new experimental branch feature-gtk3 from GitHub. Installing this branch is straightforward: Download zip-file and unpack Run autogen.sh, then run make Create virgin directory $HOME/tmp/gtk3/ and…

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Analysis And Usage of SSHGuard

To ban annoying ssh access to your Linux box you can use fail2ban. Or, alternatively, you can use SSHGuard. SSHGuard’s installed size is 1.3 MB on Arch Linux. Its source code, including all C-files, headers, manuals, configuration, and makefiles is 8 KLines. In contrast, for fail2ban just the Python source code of version 0.11.2 is 31 KLines, not counting configuration files, manuals, and text…

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ssh as SOCKS server

Assume three computers A, B, and C. A can connect to B via ssh, but A cannot connect to C, but B can connect to C. A -> B -> C On A open ssh as SOCKS-server with ssh -N -D 9020 user@B Now on A one can use brave --proxy-server="socks5://localhost:9020" The browser will then show up as if directly surfing on B thereby circumventing the limitations on A. Instead of the brave browser, one can…

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#ssh

Poisson Log-Normal Distributed Random Numbers

Task at hand: Generate random numbers which follow a lognormal distribution, but this drawing is governed by a Poisson distribution. I.e., the Poisson distribution governs how many lognormal random values are drawn. Input to the program are of the Poisson distribution, modal value and either 95% or 99% percentile of the lognormal distribution. From Wikipedia’s entry on Log-normal distribution we…

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Performance comparison Ryzen vs. Intel vs. Bulldozer vs. ARM

For comparing different machines I invert the Hilbert matrix This matrix is known have very high condition numbers. Program xlu5.c stores four double precision matrices of dimension . Matrix H and A store the Hilbert matrix, X is the identity matrix, Y is the inverse of H. Finally the maximum norm of is printed, which should be zero. These four double precision matrices occupy roughly 1.6 MB for…

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dumpe2fs: When was my hard-drive first formatted?

I repeatedly forget to remember when my hard-drive or SSD was first formatted. Command for this is dumpe2fs. This command is part of package e2fsprogs. Example: # dumpe2fs -h /dev/sda1 dumpe2fs 1.45.6 (20-Mar-2020) Filesystem volume name: <none> Last mounted on: /boot Filesystem UUID: 83a1bedb-6fd3-46d0-8900-e4e09536168e Filesystem magic number: 0xEF53 Filesystem revision #: 1…

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#dumpe2fs

Unitymedia und SIP VoIP

Folgendes schrieb ich an die Firma Unitymedia, jetzt Vodafone: ich möchte gerne meine Rufnummer XXX über meine YYY Telefonanlage via VoIP betreiben. Ich verwende den von Ihnen bereitgestellten Router “Vodafone Station”. Meine Kundennummer lautet ZZZ. Ich benötige nun folgende sieben Informationen: 1. Domain 2. Registrar 3. STUN-Server 4. Outbound-Proxy 5. SIP-UDP Port 6. Benutzername 7.…

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#Unitymedia

Windows 10 very slow after reboot

I repeatedly noticed that my Microsoft Windows 10 laptop is noticeably slow when restarted. This time I rebooted the laptop and just watched what happened in task manager. Below are the results.

Waiting for more than 10 minutes doing nothing: one third of the machine is loaded with managing its own.

Curious what might cause this obscene activity, noticed that “WMI Provider Host” consumes more…

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#blue screen #boot #slow #Windows 10

Statistics of this Blog: Crossed 110.000 Views

This blog was viewed more than 110.000 times since its inception and had more than 84.500 visitors. The averages per month are:

The most popular posts this year are:

The most popular posts over all years are:

Distribution of countries accessing this blog over last 365 days, USA is number one, followed by Germany and India:

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Configure boot settings in UEFI

Main source for trouble-shooting is Arch-Wiki UEFI. It describes the commands:

bcfg within UEFI shell

Linux command efibootmgr

1. Highly recommended to install the UEFI-shell, which is in package edk2-shell. On Asrock copy

cp -p /usr/share/edk2-shell/x64/Shell_Full.efi /boot/shellx64.efi

So name of the shell should change to shellx64.efi, at least on Asrock system A300M.

Create UEFI boot…

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SSD Speed on Dell XPS 13 9350 with Samsung EVO 970 Plus

In continuation of blog-post SSD Speed on Dell XPS 13 9350, here are performance measurements for a Samsung EVO 970 Plus in Dell XPS 13.

Caveat from Dell xps 13 9350 and Samsung 970 evo M.2 nvme Compatability?:

However, be aware that although the XPS 13 9350 uses a PCIe x4 configuration for its NVMe interface, the lanes are run in power saving mode, not max performance mode, and this cannot be…

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Blocking IP addresses with ipset

In Chinese Hackers I mentioned that I block ssh attackers with the help of fail2ban. Unfortunately, fail2ban uses iptables to create firewall rules in “Chain f2b-SSH” for each individual IP address. For a modern processor this is no problem, even if you have thousands of these rules. While for a low powered ARM processer this can have a noticeable influence on network performance. In Using Odroid…

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ASRock DeskMini A300M with AMD Ryzen 3400G

Below are some photographs during assembly of the Asrock A300M with an AMD Ryzen 5 Pro 3400G processor.

The Asrock web-site detailing the specs of the A300M: DeskMini A300 Series.

Three noticable reviews on the A300M:

Anandtech has a very readable review of the A300M: Home> Systems The ASRock DeskMini A300 Review: An Affordable DIY AMD Ryzen mini-PC

A short review from Techspot: Asrock…

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Elmar Klausmeier