A post about some maths homework caused some consternation and confusion on one of my local facebook groups:

Lots of people seemed to think this was far too advanced for a 9-year-old, or that solving such puzzles would have no applications in real life.

I beg to disagree.

Yes, I …

The spammers who try to flood my inbox must be getting desperate - they're offering to stop if I pay them!

From: "Admin" <admin@secureserver.eu>
Subject: I will stop spaming you

I'm sick of sending spam...

If you send me $10 USD worth of XMR / Monero I will remove …

The other day I came across a new English word. This is not a new thing for me - it happens on a annoyingly regular basis. But it made me stop and take notice: BLURPLE !?? Why hadn't i ever heard that before?

OK - so it sounds some combination between blue and …

A Californian woman is allegedly suing her own parents because she is ugly!

At least that is what the article claims... It is hilarious and plays into our biases about people from the USA to be litigious and generally a bit weird.

Alas, it is fake news. Or to be …

The scenario: Your server is not working right: You cannot start new processes! Simple commands like "ls" fail:

yourname@yourserver:~$ ls
-bash: fork: retry: Resource temporarily unavailable

This is a symptom of the kernel reaching the maximum number of processes. On most systems, this is 32768 processes, and on 64-bit …

The wolderful flexibility of being able to mount file systems at any point in the file system comes at a small cost: You can end up hiding files - usually by mistake.

For example, imaging having the following file systems:

• / - the root file system. A small(ish) partition, usually only a …

The situation: df (which shows disk usage) disagrees with du (which shows disk space taken up by files). So you have disk space which is "used", but it is not taken up by any files!? What gives!?

For example:

root@xps:~# df -h /tmp
Filesystem               Size  Used Avail Use% Mounted …

When investigating disk usage issues on a very full disk, the investigation may actually be hampered by the lack of disk space. For example:

du -x -m / | sort -nr | head -25

can fail if you have a lot of directories and your disk is completely full: sort will only process …

Sometimes your disk usage does not add up - for example:

karl@someserver:~$ df -h /
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda1        52G   49G  243M 100% /

So what gives? 49Gb + 248Mb is definitely less than 52Gb !! This is a sizeable discrepancy of at least 1.5 Gb!

Also, the …

Let us assume you already figured out where your disk space went.

Cleaning up disk space is easy: You just delete stuf, right?

Well.. Mostly. There are a couple of things to watch out for:

• Deleting important stuff is ... bad. You still want a working system, right?
• Deleting files that …

Imagine the scenario: Your application does not work, and no errors are appearing in your log files. In fact: nothing new is appearing in your log files! Bah!

And then you discover that your root file system is full. And that's the only file system on the box:

Filesystem     1K-blocks …