Ubuntu 14.10 cryptswap1 With LVM Stops Working After Reboot

26. Januar 2015 in Administration, GNU/Linux.

Today I rebooted an Ubuntu 14.10 that was set up with LVM and encryption.

It was unable to use the encrypted swapspace cryptswap1, which ultimately halted the boot procedure with a prompt (S for skip and M for manual resolution, i.e. single-user-mode prompt).

The problem appears to be that the UUID (blkid) of the designated swap device is lost (destroyed by overwriting). This may not become apparent after the first reboot, because data actually has to be written to the device in order for the problem to appear. At last that is my working hypothesis on why this did not bite me earlier.

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Why I Support Devuan

17. Januar 2015 in GNU/Linux.

I support the activity codenamed “Devuan” because I see it as an effort of keeping SystemD optional on Debian-based GNU/Linux installations.

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Filtering and Rate-Limiting ICMPv6 on a GNU/Linux Server

13. Januar 2015 in Administration, GNU/Linux.

Introduction

ICMP (Internet Control Message Protocol) in IPv6 is used for a variety of purposes. As opposed to IPv4, support for some of the applications of ICMP by nodes participating in an IPV6 network is mandatory. On the other hand, due to the security-relvant nature of some of the applications, where in IPv4 it may have sufficed to simply allow or disallow all ICMP traffic or certain types of ICMP packages, deeper inspection of ICMP traffic is required in IPv6.

In the following I draft an example of a set of rules for a Linux netfilter firewall on a simple, standalone application server (not a virtualization host).

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Umstellung des Telekom-Anschlusses auf “All-IP”

10. Januar 2015 in Administration, Technik.

Problem

Unser Telekom-Anschluss wird von ISDN mit ADSL 2+ auf “All IP” umgestellt, das heisst ADSL 2+ Annex J (ohne Splitter) mit Telefonie über IP (SIP).

Wir haben uns dazu bereit erklärt, die Umstellung mitzumachen, und ich möchte bei dieser Gelegenheit intern auf IP-Telefone umstellen:

  • Die Verwendung von IP-Telefonen erlaubt es, das LAN für den Anschluss von Endgeräten zu nutzen.
  • Telefonie und PCs können enger miteinander verbunden werden (spontan fallen mir da der Abgleich von Adressbüchern zwischen PCs und Telefongeräten und das Nutzen von PCs als Telefongeräte ein).
  • Eine Ausnahme ist das analoge Faxgerät.

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Support For Multiple Languages in WordPress

7. Januar 2015 in Programmierung, Technik.

Introduction

Foreign visitors have pointed out to me that they sometimes read my blog using translation functions in their their webbrowsing software, most notably “Google Translate” which is directly built into Google Chrome. That translation function does a good job, but sometimes produces oddities, for example it attempts to translate my lastname, which is also a valid German vocable.

That problem was quickly addressed by adding the class=”notranslate” plus the HTML5 language attribute translate=”no” to a <span> surrounding my name. But this incident contrasted a deeper problem that has been troubeling me for a while now.

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Mobile Version 2.0: jQuery With Specialized Plugins

6. Januar 2015 in Programmierung, Technik.

I have rewritten the mobile version of this website.

Changes in Version 1.9

  • Progress: Content updates are loaded into the existing DOM using AJAX improving loading and layout speed.
  • Progress: Swiping gesture support was re-implemented using Ramp Interactive’s excellent touchSwipe plugin for jQuery. This allows me to drop the requirement for jQuery mobile.
  • Progress: CSS was straightened up, improving layout speed.
  • Regress: There is no visual feedback for sliding, which makes swiping through the history of blog-postings less accessible but saves me the trouble of implementing a replacement for the relevant jQuery mobile FX.

Overall, the progress outweights the regress, so I put it live. :-)

Changes in Version 2.0

  • Progress: If user has enabled cookies in webbrowser, user can switch back and forth between desktop and mobile view of single post.
  • Progress: Mobile-specific Javascript is completely minified, improving loading speed.

Wanderung nach Neckargemünd, 5.1.2015

6. Januar 2015 in Sonstiges.

Vorbei am Kloster Lobenfeld auf dem “Grünen Weg” über den Heuberg nach Wiesenbach.

Blick auf Wiesenbach vom Heuberg

Blick auf Wiesenbach vom Heuberg

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Mobile Version 1.0: jQuery Mobile

5. Januar 2015 in Multimedia, Programmierung, Technik.

As an experiment, I have implemented a “mobile version” for my website with jQuery Mobile. The downside of that framework is that even the customized (stripped-down), minimized format that I am using still consumes about 200 kilobytes, and that is more than the entirety of my desktop-version start page altogether.

This excessive network traffic consumption is mitigated to some degree by the DEFLATE filter active on my webserver for everything Javascript and CSS. I also do a lot of caching, so all the framework stuff is loaded only once even though my mobile version does a page reload on every navigation action (hitting a hyperlink or swiping to a different page).

Roundabout, swiping through the first 10 blog posts consumes 520 kilobytes of network traffic, which, if you ask me, is somewhere between “Well …” and “Meh”. Being in part about music and hi-res photography, about half of my posts are featuring some sort of media, so it’s probably appropriate.

If you use one of the usual suspects in mobile webbrowsing (I mainly use Chrome on Android), the webserver should recognise this and send you off to the mobile version immediately. The mobile version then works like a slideshow that you can swipe to the right, browing backwards through the history of blog-postings. You can switch back to the desktop version at any time using the button conveniently placed at the start of each mobile page. You can also switch from the desktop- to the mobile version using the link at the bottom of every Desktop page.