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 don’t wast space on the drive. This can be useful for different application. For example …

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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 these lines: And in ~/.java/deployment/deployment.properties I changed these lines: And there is still a small …

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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 volume by Akamai. The difference was +66% in the Akamai volume. Support was not help …

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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 tags and not id3. Remove those id3v2 tags with this command: This removes the id3v2 …

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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. Solution: there is an option to disable this bug:chrome://flags/#omnibox-ui-hide-steady-state-url-trivial-subdomains Update: oogle ropped his ption. The …

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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 http://security.debian.org/ jessie/updates main contrib non-free

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” and copy the hex string after “psk=” root@server:~# wpa_passphrase WLANNAME# reading passphrase from stdinthepasswordnetwork={ ssid=”WLANNAME” …

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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 information. Pragma: akamai-x-cache-on, akamai-x-cache-remote-on, akamai-x-check-cacheable, akamai-x-get-cache-key, akamai-x-get-ssl-client-session-id, akamai-x-get-true-cache-key, akamai-x-get-request-id With this request header Akamai includes …

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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 the OS. Solution: I made a Mikrotik script that checks the status and reachabilty of …

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