Note: How to password-protect a PDF file on Ubuntu

This is a copy of this post for safe-keeping: 

In a terminal, type:

sudo apt-get install pdftk

Then, to add a password to a PDF file, type:

pdftk <input-file> output <output-file> user_pw <password>

Example:

pdftk input.pdf output output.pdf user_pw 1234

Note: 5 ways to check available memory in Ubuntu

Source (of the pictures too): https://vitux.com/5-ways-to-check-available-memory-in-ubuntu/

1. free -m

2. vmstat -s

3. cat /proc/meminfo

4. top

5. htop

How to get the RSS feed out of iTunes?

I found the solution here: https://superuser.com/questions/78415/get-rss-feed-from-itunes-podcast-links

It is to use this website to extract the RSS feed for you: http://itunes.so-nik.com/

Chrome & Shockwave Flash using 100% of CPU

I'm just making a note here:

Shockwave flash running on Google Chrome uses about 100% of my CPU capacity.

This causes the cooling ventillation to run high speed, which produces much noise, and it also causes the machine to gain a quite high heat.

NOTE: Making movies from image files using mencoder / ffmpeg

Here's a site. It describes something I wanted to do / did half a year ago but made no blog-post of it.

What I originally wanted to do was to have a single image as a video, and put some music to it and post it on youtube.

I somehow managed it, but I have no idea anymore how.
And I also found mp3tube, so I don't really need this anymore, if I don't care to have a special picture for my music.

Notice: pdfnup --trim

It removes a given amount of margins on the side, with the syntax 'left bottom right top'.