My name is Philipp C. Heckel and I write about nerdy things.

Posts Tagged / Linux


  • Feb 01 / 2011
  • 3
Administration, Linux, Programming, Security

Altering old SVN revisions: removing confidental data from a Subversion repository

Version control systems like CVS or Subversion are designed for keeping track of the changes of a project and for having the possibility to revert to old revisions if something goes wrong. In contrast to regular relational databases, these systems are made only for adding new content to a repository, and not for removing data from it. In fact, deleting old content is not a built-in functionality in SVN, and mostly requires removing entire revisions from the repository or even creating a new one.

But what happens if you accidentally commit a password or other sensitive information to a repository? This post explains how to remove this confidential data permanently from the repository by simply overwriting it in old revisions, i.e. without having to remove revisions or create a new repository.

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  • Jan 12 / 2011
  • 3
Linux, Multimedia, Scripting

Picasa for Linux: Export albums in sort order

As one of the best picture organizers out there, Picasa is (in my opinion) almost complete in terms of features and has a nice look and feel at the same time. Even though Google stopped developing the Linux version after 3.0, it still works perfectly using Wine and a couple of cp-statements.

However, as stated many times by Picasa users and bloggers [1,2,3,…], Picasa’s export function misses a tiny little feature that maintains the sort order of the album when exporting it to a folder. Instead of renaming the pictures to keep them sorted in normal file managers (by name), Picasa just copies the files of an album to one folder and thereby destroys the order. As if that wasn’t enough, Picasa also overwrites duplicates filenames from different source folders.

This missing feature has even led to small standalone projects that fix this issue, e.g. Picasa Independent Album Exporter (PIAE) and Picasa Order Preserver. While both applications do their job, both are a bit heavyweight, and PIAE only works for Windows (and not on Wine).

This post presents a tiny little Perl script that renames pictures of an exported album according to their Picasa sort order.

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  • Jan 28 / 2010
  • 2
Administration, Linux

How to: Postfix as mail relay with greylisting support using SQLgrey

Greylisting is a very efficient technique for fighting spam and can reduce the spam messages in your mailbox by more than 90%. It uses the fact that most spammers only try delivering their spam-mails once, whereas real mail transfer agents (such as the ones regular e-mail service providers are using) try delivering each message up to 4-5 days before they give up.

I have always wondered why most ESPs don’t offer greylisting for their mailboxes, but only rely on less effective and resource-hungry post-retrieval filter methods. Unfortunately, my e-mail provider is one of them so that I get at least a couple of spam mails a day …

Luckily, it is very easy to set up your own mail relay with greylisting support, i.e. a mail server that simply forwards the mail to your real provider once it passes the greylist-filter.

This little tutorial describes how to set up Postfix and SQLgrey as mail relay.

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  • Sep 21 / 2009
  • 8
Linux

Dell Latitude E6400: the Ubuntu fan and noise problem

A couple of days ago, my 4 year old laptop (HP nx8220) decided that it was time to retire and refused to switch on a couple of times. Even though it works most of the time, I can’t rely on it anymore and will therefore look for new notebooks in the next week.

On my journey through the Web I looked into the details of various business notebooks. I stumbled across the Dell Latitude E6400, which looks nice and has everything I wanted. Unfortunately, it also seems to have problems with Ubuntu. In particular, the fan seems to run all the time (and not too slow, but very loud) – as many forum posts and user reviews prove [1,2,3,4].

Since I couldn’t find a solution, I decided to ask the Dell support via their support chat.

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  • Aug 09 / 2009
  • Comments Off on Extract text from PDF files
Linux, Office

Extract text from PDF files

Adobe’s Portable Document Format (PDF) has reached great popularity over the last years and is the number one format for easy document exchange. It comes with great features such as embeddable images and multimedia, but also has rather unpleasant properties. The so called Security Features represent a simple Digital Rights Management (DRM) system and allow PDF authors to restrict the file usage. Using the DRM system, authors can allow or deny actions such as printing a file, commenting or copying content.

Even though this is a good idea for some situations, most of the times, it’s just annoying: Collecting ideas for seminar papers or a thesis, for instance, is almost impossible without being able to Copy & Paste certain paragraphs from the PDF.

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  • Apr 07 / 2009
  • 2
Linux, Scripting, Security

Simsafe: Simple command-line password safe

Nowadays, it appears to me as if almost everything in the big and fancy world of IT comes with the need to sign up and create an account. Every little online tool, every social networking site and of course every instant messenger account. System administrators hits it even harder: The setup of a server machine requires to create lots of different users for every kind of service, — be it Postfix, Sendmail, Courier, MySQL, PostgreSQL, etc. Most of them require some kind of super-user password or account.

This is where a password manager comes in handy: Open the password vault by typing in the master password, put in all you secrets and crucial information, save it and be happy. As if!

Almost every password manager I found on the Web was crowded out by details so that it took minutes to add a single account. What I wanted was something like a text-file with password — and that’s what I made: A simple command-line password safe.

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  • Oct 25 / 2008
  • 3
Linux, Synchronization

Unison & multiple hosts: “Warning: inconsistent state.”

As some of you might know, Unison is this great tool that allows bidirectional synchronisation of two hosts, – no matter which operating system they’re running… Well, at least the well known ones are supported.

Since Unison can also be used to sychronise more than two hosts, it’s perfect for big amounts of data that has to be shared in a team.

A scenario like this is possible and works for me: UserA <-> Server <-> UserB.
But of course, also other users could sync with the server. Unison rocks!

Today, after reinstalling his OS, my friend got the following error message:

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  • Sep 30 / 2008
  • 48
Linux, Office, Scripting, Synchronization

GCALDaemon deb-package for Ubuntu/Kubuntu

GCALDaemon (project doesn’t exist anymore, was at http://gcaldaemon.sourceforge.net/) is a great tool to synchronize many of Google’s services such as Google Calendar and Contacts with your local PC. Unfortunately, the installation on Ubuntu/Kubuntu and any other Linux distribution is still not the most comfortable. For this reason, I sat down some hours and packed the tool into a deb-package and additionally added a nice command line tool to simplify some of the basics.

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  • May 16 / 2008
  • 4
Office

Launch Nautilus in the current working directory

Working on the console is sometimes tiring, especially when you have to rename files. Using Nautilus is much quicker for these types of actions. The problem is, that if you’re working in a deep depth of your file tree and your path is very long, it may take you some extra seconds to open this path in the Nautilus browser. So wouldn’t it be much easier to simply type naut on the console to open Nautilus with the current working directory?

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