Tips & Tricks. Link to RSS feed


Limiting per User Memory with Cgroup

Sat, 24 Jan 2015 11:42:06 +0100Posted by André Landwehr

[Tips & Tricks]

I teach my test engineers programming in C and recently introduced malloc. Since they don't have Linux machines themselves I gave them logins on my Desktop where they can do the exercises. A few days ago, one of them called malloc in a loop, bringing up the OOM killer and effectively killing my xserver on the way. Call it collateral damage, but it was about time to limit other user's memory...
Ulimit comes to mind first of course, but ulimit only limits the amount of memory per process, which is not really what I wanted to do. There is a relatively new mechanism called cgroup, which looked...

Locating Houses

Wed, 02 Jul 2014 07:12:30 +0200Posted by André Landwehr

[News] [Tips & Tricks]

We decided to stay in the area of Minden and thus we're looking for a house to buy. It's great that the real estate brokers show their stuff on the web nowadays, but unfortunately they don't add the address. Doh. Thanks to several free maps available on the net, this fortunately is only a minor inconvenience and not a showstopper anymore though.
When trying to locate a house, start with a map showing the area covered by the postcode (the brokers offer that information at least). Now look at the pictures showing the outside of the house. When you're lucky, there is a bus stop or some other...

The Dock

Mon, 17 Mar 2014 19:08:25 +0100Posted by André Landwehr

[Tips & Tricks]

The Note 10.1 2014 has the micro USB port on the bottom side, below the buttons. I can think of few more stupid positions for the single most important port the tablet has (yes, there is a second port: audio line out...), since it is essentially unusable when the tablet is used with any normal cover. The only reason I can imagine why Samsung put it there is to make people buy a docking station. Which I did.
Well, sort of.
I bought the original Samsung docking station, advertised as compatible to my tablet, which has a micro USB plug on the front side where the tablet can be placed on and a...

Debian on the Galaxy Note 10.1 2014 Edition

Thu, 27 Feb 2014 20:44:34 +0100Posted by André Landwehr

[Tips & Tricks]

My trustworthy IBM X41 Laptop served me for 12 years now, and although it never gave me reason to mistrust it, I do know that moving parts like hard-disks have a limited lifetime. So better don't stretch the luck any further I thought and invested into the next generation - the most powerful tablet hardware I could find at the time, a Samsung Galaxy Note 10.1 2014 Edition. So, a quadcore CPU and massive 3 GB of main memory, that should make up a pretty decent Linux desktop, shouldn't it? Well, yes, but beware the pain...
I'm writing this email in Thunderbird (or actually icedove) running...

Magento

Sun, 22 Dec 2013 20:14:19 +0100Posted by Andre Landwehr

[Tips & Tricks]

This weekend was dedicated to installing the famous Magento shop for Cardlove. Turns out this is not so easy at all. There is a pre-built version for using in Germany, with all the extra legal stuff required only here. You can find it for free at nr-apps.com. Currently this is based on Magento 1.7, which is not quite the latest stable release. They present four zip files for download, without any further comments. Turns out these are just different versions of the same, so I chose the latest one (magento de 1 2 1.zip).
The next pitfall for the unwary is that after unzipping the file inside the...

Joining multiple JPEGs into a multipage PDF

Sat, 10 Aug 2013 13:18:46 +0200Posted by Andre Landwehr

[Tips & Tricks]

If you ever wondered how to convert multiple JPEG files (e.g. some scanned in pages) into one big PDF file, and not all of these have the same resolution, you might have had a hard time figuring out how to do this with free software under Linux. Here is the solution:
First, convert each invidual JPEG into a PDF:
for I in *.jpg; do BASE=`echo $I | sed -e 's/.jpg//'`; convert "$BASE.jpg" "$BASE.pdf" ; done
Then, join all the PDFs together into one big document:
pdftk first.pdf second.pdf third.pdf fourth.pdf cat output combined.pdf
Using this combination of tools gave the best results for me,...