Linux: ZFS: Be Careful With Child File Systems

 Computing, Linux  No Responses »
Sep 012016
 

One of the advantages that ZFS brings, is that it is so easy to create file systems, that you can create them for purposes that you would not previously do. For example, I have an additional file system mounted under my home directory for a certain application that generates a lot of data that I do not need backed up. Because the script I use to back up stuff does not cross file system boundaries (i.e. it does not descend into a directory that contains a mounted file system), I can simply exclude a large amount of frequently changing data by making a file system.

Or I might (as it happens I do not, but I could well do) create file systems for large lumps of data to easily see how much space they occupy – perhaps ~/Pictures. You can run a command like du -sh ~/Pictures, but that is an expensive command (it takes a while) and it tells you how large the files are; not how much space they occupy on disk. And on-disk compression can make that a significant difference! So simply run df -h ~/Pictures if that directory is on a separate file system.

But there is a bit of a gotcha with that. If you create such file systems in the normal way (such as zfs create pool/mikes-pictures; zfs set mountpoint=/home/mike/Pictures pool/mikes-pictures) you risk creating a situation that may prevent your home directory from mounting. If the “child” file system is mounted before the parent, it will not be possible for the parent file system to be mounted when booting.

Instead create the hierarchy properly :-

zfs create pool/h2
mkdir /h2
zfs set mountpoint=/h2 pool/h2
zfs create pool/h2/mike
zfs create pool/h2/mike/Pictures
ls /h2/mike/Pictures

You will also have to fix the permissions, but this is a far safer way of organising things suitable for future file system creation.

damascus-unix-prompt

Linux: Fixing The Invisible Mouse Pointer

 Computing, Linux  No Responses »
Aug 292016
 

It seems that occasionally GNOME can go a little screwy and its fancy mouse pointer plugin can result in an invisible mouse pointer. Which makes doing anything just a little bit tricky.

If you can open a terminal, enter the command :-

gsettings set org.gnome.settings-daemon.plugins.cursor active false

And all should be well. At least until it decides to turn itself back on again (so make a note of this fix!).

damascus-unix-prompt

Scrapping The Human Rights Act

 General, Politics  No Responses »
Aug 232016
 

There are moves afoot to scrap the UK’s Human Rights Act.

Think about that for a moment. There is a minister of justice who wants to take away your human rights.

Whether or not you like the ECHR, the fact that a British politician wants to scrap the Human Rights Act is somewhat worrying. They want to take away our human rights. It is all very well saying that the British authorities never behave in ways that would threaten our human rights, and we have both common law and traditions that protect our human rights. But scrapping the Human Rights Act sends a signal that we do not need human rights; a signal that may not be picked up and acted on for years or decades, but the signal is still there.

Now if they were merely going to modify the Human Rights Act, that would be fine. I am sure there are parts that go a bit too far and others that do not go far enough. The key thing is that changing the Human Rights Act; even improving it, sends a different signal no matter what those changes are. That signal is that we do believe in human rights.

And that is a good message to send.

The New Defence

The New Defence

“Not Guilty” Means “Innocent” ?

 General  No Responses »
Aug 192016
 

Of course it doesn’t. Anyone who claims so needs their brain rebooted.

This topic came up on an online discussion where there were many comments indicating a poorly conceived belief that a “not guilty” verdict from a court means “innocent”.

In a criminal case the court has to decide whether there is enough evidence to determine if the accused can be found guilty in the opinion of the court. The legal system very wisely knows that whilst it has the job of determining truth (as part of dispensing justice), it cannot do that so restricts itself to determining whether there is sufficient evidence to find someone guilty beyond reasonable doubt.

That means those who get a “not guilty” verdict comprise two groups – those who are innocent, and those who are guilty, but there is sufficient doubt over their guilt that they cannot be found guilty. Any policeman (or woman) will tell you that those found “not guilty” include plenty of people who really are guilty, but the evidence isn’t sufficient.

We have a legal system where there is a presumption of innocence – the old saying is that it is better that 99 guilty criminals go free than 1 innocent person be convicted. The legal system assumes that mistakes will be made (quite rightly – the decisions are made by people), and weighs the system heavily in favour of ensuring that mistakes result in people going free when they are guilty.

It does this by asking the jury to decide if the accused is guilty; not whether they are innocent. And they must have no reasonable doubts over the guilt of the accused. In a perfect situation a simple question has a black or white answer – the accused is guilty or innocent; in the real world we all know there are grey areas – there is plenty of evidence showing that the accused killed the victim, but she has a good alibi.

Where a case becomes grey and there is sufficient doubt, the verdict should be “not guilty” even if the accused was probably guilty.

The Edge

Tips On Staying Cool …

 Humour  No Responses »
Jul 192016
 

(because everyone else has some)

  1. Stay in the shade; the big shiny thing in the sky is the heat source.
  2. If you are in the sun, wear white; it absorbs less of the heat from that big shiny thing. See point#1.
  3. If you are in the shade, wear black; it radiates more heat. See point#1.
The New Defence

The New Defence

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