Category Archives: Technical

“Rational” IT related entries.

Apache Guacamole: RDP printer not working, “error parsing HTTP request header”, “Invalid character found” etc

If you’re using Apache Guacamole 1.0.0 behind an nginx reverse proxy, and Guacamole’s RDP printer doesn’t work, and browser console logs error 400, welcome to read further.

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Apache Guacamole: how to change the default URL path (/guacamole) to something else

Say you want to change Apache Guacamole’s URL from http://server:8080/guacamole to something like http://server:8080/my-hidden-guacamole-instance (or perhaps you’re using nginx to proxy requests to Guacamole / Tomcat and you don’t want any path at all).

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macOS High Sierra: Spotlight search not working — “Database mapping failed” error spammed to the system log

Solution can be found here (read the post that starts from “I’ve solved this…” by Design Complex).

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macOS High Sierra doesn’t start after updating (stuck on Apple logo) — “failed to unwrap volume key” error

The first thing you want to do when your Mac system doesn’t start is to start up into the verbose mode to see if there any error messages. Don’t try to fix the problem before diagnosing!

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Windows Server 2019: RD Session Host — ChangeMode “Invalid operation” exception

If you’re changing the client access licensing mode of your RD Session Host using the PowerShell $obj.ChangeMode(…) command and it fails with an error saying “Exception … Invalid operation”…

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“Install %OS%.app does not appear to be a valid OS installer application” (createinstallmedia error)

If you’re trying to create a bootable installer for an older macOS version (like El Capitan) with createinstallmedia, and it fails with a “does not appear to be a valid OS installer” error, quite possible the actual problem is that … Continue reading

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Downgrade any Homebrew package easily

I’ll use Tesseract as an example, but the same logic can be applied to any other Homebrew package.

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“MagickWand shared library not found” on uwsgi

If you’re getting this error while deploying a Python app on uwsgi: MagickWand shared library not found. You probably had not installed ImageMagick library. Try to install: apt-get install libmagickwand-dev It may not be what it seems: Wand’s load_library() function … Continue reading

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Make VLC show the title of a streaming video

I’ve created a tiny VLC extension that makes VLC show the title of the currently playing streaming video. It allows you to set custom titles even for the streams that you don’t own (e.g. from YouTube). For more information, see: … Continue reading

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Kerio Connect server connection errors after upgrading to version 9.2.6

Kerio Connect 9.2.6 introduced a limit for a number of simultaneous connections from a single IP address, which is — by default — set to 100 per protocol. If more than a hundred of users start using Kerio Connect from … Continue reading

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