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Andreas 'ads' Scherbaum

GNU parallel allows you to multiplex tasks, and possibly use more CPU resources to speed up the task at hand. This works if your task can be split down into multiple independent tasks which otherwise will be executed serially.

An example: you find files in a directory, and want to compress all of them:

find /path/to/directory -type f -exec bzip2 -9 {} \;

Above line will find all the files, and compress each of them, one after the other. Most modern systems have multiple CPU cores installed, but nevertheless above line will only use one of them. GNU parallel solves this by multiplexing the task, and starting multiple compress processes. Above line changes to:

find /path/to/directory -type f -print0 | parallel -0 --no-run-if-empty bzip2 -9 :::

By default, parallel will start as many parallel processes as CPU cores are available. The --jobs option can be used to specify a hardcoded number (as example: "8"), or limit the number depending on the number of available cores ("-2" will start 6 processes if 8 cores are available, "+2" will start 10 processes if 8 cores are available).

However when you start "parallel", it will nag you that you confirm that any time you use it for processing data for an academic article, you have to cite "parallel":

Academic tradition requires you to cite works you base your article on.
When using programs that use GNU Parallel to process data for publication
please cite:

  O. Tange (2011): GNU Parallel - The Command-Line Power Tool,
  ;login: The USENIX Magazine, February 2011:42-47.

This helps funding further development; AND IT WON'T COST YOU A CENT.
If you pay 10000 EUR you should feel free to use GNU Parallel without citing.

To silence this citation notice: run 'parallel --citation'.

That's ok if you use it manually, but in a server environment no one will ever see this note.

Andreas 'ads' Scherbaum

Most of my systems run on a software RAID 1 configuration (that is, two disks, where each disk is mirrored to the other). This way, one of the disks can fail and still all the data is available.

If a disk failure happens, the disk is replaced with a similar disk, and then needs to be configured and re-added to the RAID.

Newer systems all use the GUID partition table (GPT), and therefore allow almost unlimited disk sized. Instructions for re-adding a disk using GPT are a bit different from the days when MBR (up to 2 TB disk space) was used, therefore I'm writing them down here for future use.

Andreas 'ads' Scherbaum

A while ago I asked for recommendations for Android Podcast apps. From all over the Internet I got a great number of recommendations, and looked into all of them.

Andreas 'ads' Scherbaum

While diving deeper into my openHAB installation, the need for notifications on mobile phones came up. After some research, I settled with Pushover, which provides Android and iOS apps, as well as Desktop notifications. openHAB Rules have support for Pushover, and everything works well together.

Except when Android decides to kill apps, because they sit idle and do nothing. It so happens on my Huawei phone that notifications are delivered to the device, but no popup shows up. Only when I open the up, suddenly all the messages are there. The Pushover FAQ has an entry for this, even for Huawei phones, but it is outdated.

Andreas 'ads' Scherbaum

Ansible comes with a plugin which allows to create and renew Let's Encrypt certificates. Documentation is sparse, so I decided to post about my own Playbook.

Andreas 'ads' Scherbaum

Up until recently I was using an App to clean the the Android cache once in a while. If you don't, the device over time get's sluggish, because too many apps store too much data in the cache. Over time this cache can grow to GBs in size.

On the other hand, every single "clean cache App", over time, started showing more and more aggresive advertising. I get that the developer wants to make some money, that's fine. But maybe the money is not enough, so more advertising it is.

Turns out, there is a built-in way in Android to clean the cache. No need for an extra App.

Andreas 'ads' Scherbaum

Recently it was time to refurbish our email infrastructure. For a very long time I was hosting everything for myself, but things don't get easier and over time even the spam filters couldn't catch up. Therefore I looked into a number of hosted services, and in the end settled with Google Gmail.

Andreas 'ads' Scherbaum

Recently smplayer (not mplayer) started behaving strange: every video started muted. Pressing the mute button (m key) really muted the sound, pressing the button again unmuted the sound and the audio started playing. This behavior persisted over restarts of smplayer.

Now that is really annoying!

Andreas 'ads' Scherbaum

I'm a (more or less) happy KDE user, ever since the KDE 3 days. Before that, I used fvwm2 for a long time, but that is a different story. It also happens that I never really reinstalled my home directory - the oldest files I can find are from 1997, and that is pretty much when I switched from an old Slackware system with self-compiled updates, to something with a more modern distribution. That means, that all the time from 1997 to today, I carry the same /home/ads across my computers. The home directory grew from a few MB to 133 GB today (maybe I should clean it up, but then again it's cheaper to buy a bigger harddisk).

It also means, that I never deleted my KDE config, even when upgrading to KDE 4 or Plasma.

Andreas 'ads' Scherbaum

For quite a while now, my wife and I were using Trello to keep things organized. We both had our private lists and boards, and also a few shared boards for joint tasks. Over time we realized that this tool is more annoying than helpful, and we decided to try something else. After a lengthy discovery phase we settled with Wunderlist.

There are a few requirements we have for a to-do list tool:

• Shared boards/lists
• Managed using a Website, obviously
• Android app, possibly iOS app
• Proper notifications, as in configurable alarms and separate notification per task
• Subtasks and checklists
• Attachments
• Option to assign a task to someone else
• A bit more fancy and modern interface than Trello has

All in all not very advanced features, all basic stuff.