Author Archives: alex

Sparse Files Howto

Unix file systems like ext3/4 can store files which are partly empty more efficiently by not storing blocks with all zeros. These files are called sparse files. When reading these files every things works as normal but “all zero” blocks … Continue reading

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DELL iDRAC6 with Java8

Problem: The remote console feature of a Dell R710 server does not open with an Linux client with errors like these: Connection failed, Unsigned Java Applett, etc Solution: I had to change three things:in /usr/lib/jvm/java-8-openjdk-amd64/jre/lib/security/java.security I had to change to … Continue reading

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Akamai High Traffic Volume

Problem: Akamai is showing very high edge traffic volume, but other sources of accounting show less traffic, and Akamai is billing this high volume! Discussion: I activated log shipping to compare the volume of the shipped data, to the reported … Continue reading

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Remove ID3 Tags from Flac Files

Problem: Some flac players refuse to play some flac files, and even tools like an old ffmpeg can’t handle some flac files Solution: These flac files might have id3v2 tags which they realy should not, because flac uses vorbis style … Continue reading

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Block Internet per User/Service

If you like to block network access for certain users on a linux box it’s as simple as that: /sbin/iptables -I OUTPUT -m owner –uid-ower <USERNAME> -j DROP Username might also be the username of a running service.

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Chrome Destroys URLs in the Location Line

Problem: current Chrome browsers cut URl parts and hide the correct URL. https://www.derstandard.at/ is shown as derstandard.at. This is simply wrong from the technical point of view. And it might even be dangerous for some URLs form a security standpoint. … Continue reading

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APT sources list

Problem: when debian goes from “testing” to “stable” to “oldstable” the package sources change. eg. jessie-updates are remove, same happened to jessie-backports The current file /etc/apt/sources.list for jessie (currently oldstable) could look like this deb http://ftp.debian.org/debian/ jessie main contrib non-freedeb … Continue reading

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Configure WLAN Statically in Debian/Linux

If you want to configure WLAN settings on a Linux machine statically you can use the normal /etc/network/interfaces configuration method of Debian. For WPA-PSK you can use this 3 steps: Install the “wpasupplicant” package Generate a psk line with “wpa_passphrase” … Continue reading

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Debugging Akamai

Akamai just works, … most of the time. But sometimes you have to check what’s going on, and Akamai gives you a handy tool for this. There is an HTTP request header that tells Akamai to respond with some internal … Continue reading

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MikroTik Automatic IPSec Failover

Problem: Mikrotik allows only one ipsec policy per network-to-network pair. If you want to have redundant tunnels between two locations with two upstreams you cannot configure ipsec redundancy on Mikrotik because one ipsec policy is always marked as “invalid” by … Continue reading

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