Entries filed under category “Userland”:

Performing push backups – Part 2: rsnapshot

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After I discussed a possible backup solution using rdiff-backup in the last part of this series I want to show you the second tool which is rsnapshot.

As I already pointed out, I'm not using rdiff-backup anymore. The reason is mainly that it is simply too slow. I'm using a Raspberry Pi as my NAS and it is absolutely not capable of handling larger backups with rdiff-backup. It works for smaller backup sizes, but not for my entire home directory. Even when I pushed the initial full backup directly to the backup disk (not using my Raspberry), all future incremental backups were still unbearably slow. Even when no files changed at all, it took hours over hours for simply comparing all the files I had in my home directory to those on the NAS, whereas a full comparison using rsnapshot is done within five to ten minutes. Now keep this in mind and look at the fact that incomplete backups made with rdiff-backup can't be resumed. You could imagine that in the end you wouldn't have any backup at all. Basically all rdiff-backup would do is to compare and push your files over the day and abort in the evening when you shut down your workstation. And then the next day it would spend all the time reverting the incomplete backup and running another one which might not finish either.

So this is the main reason I stopped my experiments with rdiff-backup. It was a nice time, but I finally moved on. Therefore say hello to our new precious star: rsnapshot!

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Performing push backups – Part 1: rdiff-backup

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Backups are a very vital part of every computer system, be it a corporate PC network or simply your local workstation. Unfortunately, they are often neglected, although everyone knows how important they are. The “I haven't had any bad incidences yet, but I know I really should… guess what… I'll do it next week” attitude is only too well known by everybody, including myself.

Performing backups is a tedious process if done wrong. Thus backups need to done automatically in the background without any user intervention. As soon as someone feels the need to do something in order to get his stuff backed up, he will ultimately end up with no backup at all (and probably a bad conscience he only forgets too fast).

In this little two-part article series I will present two tools I've been playing around with a lot and I'll show you how you can use them to set up your own personal NAS with a spare piece of hardware such as a Raspberry Pi. No need for any expensive special storage system.

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Programmatically limit CPU usage of certain processes

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With KDE 4.10 the file indexer has undergone some major changes which made it pretty usable so I decided to switch it on again. It turned out that the first stage indexing works exceptionally well. It indexed about 60,000 files in my home directory in the blink of an eye.

Unfortunately, I had to realize that the second level indexing does not work so well. I remember Virtuoso often eating up all my CPU in the past. Now Virtuoso keeps quiet, but nepomukindexer let's my workstation fly. It only starts indexing when my PC is idle, but for bigger files it keeps the CPU busy at a level of 100%, which is a pretty bad thing. There is already a Bug report about nepomukindexer consuming too much CPU time on larger files, but I didn't want to wait for a fix.

Long story short: I thought of ways to automatically limit the CPU usage of certain processes (not necessarily only Nepomuk).

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Hacking embedded systems

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Linux is everywhere, not just on desktops. It's on phones, ebook readers, on public terminals, on routers, on electricity meters and many more devices. The key to Linux' success is it's diversity. It is possible to run Linux on nearly every technical device that has a CPU. Many of these are closed systems, so often you don't even notice that Linux is running on that particular device, but there is always a way to gain access to its internals and modify it the way you want. But often you have the problem that heavy modifications might void your warranty or make updates to a more recent firmware version impossible. In this article I want to show you a simple but powerful way to modify such systems in a non-destructive way.

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Shell trick #1: Numbering lines in text files

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Hi, today I'll present you something new. It is an experiment and I'd be curios whether you like it. I've started a little series of ttyrecs. That means, I've recorded a little tip or trick on the console and uploaded it to PLAYterm so it can be easily played back in the browser. I thought it could be useful to do a little command line gymnastics.

Today I'll show you three ways how you can number lines in text files. We'll do that with cat, nl and vim.

Note: you need JavaScript enabled in order to play the ttyrec.

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Grep's out of date? Full ACK!

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grep is a handy tool and I use it every day. But sometimes I wish it had some more features. For instance full featured Perl compatible regular expressions (PCRE) since the current implementation is not complete and I think it will never be, automatic recursive search, exclusion of non-text files etc.

Here a tool called ack comes into play. It's a search tool and grep replacement written in Perl, which is able to do all these things. Guess what!

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Damn Flash Player! Adobe, fix it!

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Adobe Flash has ever been a great source of anger due to many bugs (see here for example) and security vulnerabilities. Anyhow, it has evolved into a widely used technology and many, many websites need it to function correctly (yeah, HTML5 is coming, let's hope it will replace Flash in many places in the near future).

Adobe's bug fixing behavior has never been great and we all know, that Flash for Linux has been permanent beta (or alpha) since we can remember, but enough is enough. There is a severe bug that has now existed for three years, reported by hundreds of users. Adobe closed this report without taking action. Now it has been reported again and I want you to vote for it. Please!

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Boot your Linux silently

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When you freshly set up a Linux distribution by hand, you get a lot of verbose output when booting into your system, but also install'n'go distributions like Ubuntu oder SUSE output some text when loading the kernel. This is not always desired and many people want to suppress these insistent system messages, but it's not as easy as you might think.

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Configuring your console pager

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The UNIX philosophy is based on the DRY principle which declares: “Don't repeat yourself”. Therefore, a program just does what it's made for and uses libraries or even other programs on your system to do a more advanced job. Some of these auxiliary programs are user definable and probably you already know the EDITOR environment variable, which specifies your default editor for the console. This is used, e.g., for the command visudo, which opens your /etc/sudoers file safely, or by svn to input a commit comment. But another important component is your console pager, which is used to display textual content on the console.

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Set up GTK application icons on KDE

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Gnome and KDE come more and more together but there are still some differences which sometimes might lead to incompatibilities between these two large desktop environments. Whereas you have relatively few problems with KDE applications on Gnome there are far more problems when using Gnome applications on KDE even though there are some compatibility engines. In this Howto Blog post I'll show you a way to converge GTK and Qt as much as possible from the perspective of a KDE system.

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