Note to self: How to update Debian KDE packages to unstable

I use Debian with KDE's Plasma desktop environment. I usually track Debian's testing repository, but often I like to upgrade the version of KDE packages installed to more recent versions in the unstable repository. My preferred way:

sudo aptitude --visual-preview -t unstable install ~i~mkde

The action tends to be independent of anything else, but that's easy enough to work around—update per usual before running.

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Using Unison with Android over USB

For some time, I've been happily using Unison in conjunction with my Android phone's USB mass storage function to synchronize files between my phone and my desktop. It was simple: I'd plug in my phone with USB and enable the SD card to be used as a mass storage device, then mount it in Linux and run Unison as if the phone was a local folder (with appropriate tweaks to support the FAT filesystem).

Alas, my phone was getting on in years (or months, as it is in tech), and with support long dropped and capacity nigh exhausted, I had to upgrade. With my new phone I've been promoted to the “new hotness” that is Android 6 Marshmallow, but one of the functions that was dropped along the way was the ability to expose the SD card as mass storage over USB. Admittedly it wasn't a perfect solution, requiring unmounting …

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Removing hostile Windows updates

As a consequence of their recent effort to boost the numbers of Windows 10 installs using any means possible, however questionable, and turn their paying customers into beta testers, Microsoft have been especially hostile to their users as of late, installing nag-screens and “telemetry” code (also known as “spyware”) under the guise of important updates to existing installs of previous versions of Windows. While I would happily eschew Windows for Linux on all the machines I use, and have largely done so, the idea of avoiding Windows in totality is, sadly, not yet practical―the common-use machines I maintain in our lab required it for various reasons, and even I still keep a Wintendo partition.

There are plenty of discussions around about what to do about this. Here's a fine example. Though this is intended for my own reference, I've had success with the following:

wusa /uninstall /kb:2952664 /norestart …

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Accessing machines on a home network with sshuttle

You might have noticed that I'm running a little Raspberry Pi, acting as a server for my website as well as some other small server-ish tasks. This machine is actually on my home network and I also use it as the front-face to that network for incoming connections. There are other machines on this network, and while they are behind a NAT and so not addressible from the outside world, this is fine most of the time. But on the odd occasion where I'd like to directly address any other machine on that network, I have to do so through the Raspberry Pi. Depending on what it is I'm trying to do, exactly, that can be tricky.

I've just discovered sshuttle. It acts similarly to a VPN, using SSH under the hood to transport TCP packets through a server that you specify. The cool thing is that it doesn't require …

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On backups/redundancy

Recent events gave me cause to consider my personal data backup and redundancy strategy for my Debian installs. Or, more accurately, it caused me to amend my half-baked and semi-implemented existing approach so that I won't lose data or have to reconfigure things from memory/scratch in the event of a hard disk failure.

My present “backup” approach is really somewhere between a time-limited backup and redundant storage. Essentially, I use Unison to synchronize my home folder (with certain sub-folders ignored, e.g. certain git repositories, config and thumbnail cache folders) between my desktop and my netbook. I have to run Unison manually, so I end up synchronizing my data every week, give or take. This effectively kills two birds with one stone: I get to have local copies of my important data as up-to-date as my last sync for when I'm on the road and using my netbook, and …

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Copying an existing Linux system to a new hard drive

I recently upgraded my home desktop's hard drive, because the old one was getting a bit full. Googling for instructions about how to transfer an existing system onto a new drive, many posts suggest using the cpio command, and that's what I tried. While this command does the job for the most part, there is one caveat which I encountered that makes cpio not the ideal tool to use.

Don't use cpio to clone filesystems. Why? Because GNU cpio doesn't support access control lists (ACLs) or extended attributes (xattrs).

Using cpio will end up a little screwy in some edge cases because of this. The particular case I ran into involved folders in /media that are managed by udisks2. udisks2 creates personal mount folders under /media with tailored ACLs to help properly manage permissions for permission-capable filesystems mounted by regular users. If you already have one of these personal mount …

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Adding the binary entropy function to LibreOffice Calc

Lately at work I've been doing some data analysis in LibreOffice Calc that requires the binary entropy function. The function itself looks like H2(x) =  − xlog2(x) − (1 − x)log2(1 − x), where 0log2(0) is taken to be 0. It's this latter point that makes things a little tricky. LibreOffice Calc doesn't have this function built-in, sadly, and you have to explicitly guard for the case where x is 0 or 1, which is not easy to pull off inside a cell.

So I wrote a basic macro that implements it:

Function BINENT(x)
    If x = 0 Or x = 1 Then
        BINENT = 0
    ElseIf x > 0 And x < 1 Then
        BINENT = -(x*Log(x) + (1 - x)*Log(1 - x))/Log(2)
    Else
        BINENT = Null
    End If
End Function

To be able to use BINENT in Calc, go to the “Tools” menu, “Macros”, “Organize Macros …

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How to subscribe any email address, including a GMail alias, to a Google group

A few of the interests I have and projects I follow use Google Groups to keep in touch. Essentially, these are just mailing lists that Google maintains. At any rate, while it's possible to subscribe to a group without having a Google account by sending an email to (group name)+subscribe@googlegroups.com, if you do have a Google account and use GMail with aliases, it can be tricky to ensure that you subscribe using your preferred address. This is because Google, in its infinite wisdom, will subscribe your GMail address if it detects you attempting to subscribe under any alias that's associated with your GMail account. That has the side-effect that you won't be able to post to the group with anything but your GMail address.

Luckily there's an alternative subscription mechanism (which I spotted here). If you instead use the Google Groups web interface, Google won't have the …

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How to find, and obliterate, large files in the history of a subversion repository

Sometimes, as I have, you'll find yourself working with colleagues who, through no fault of their own, are either not acquainted with the etiquette of Subversion repository use, or simply have an accident. What you may then end up with is a repository that contains one or more giant blobs of useless data that, really, should never have been added in the first place. Whether or not the culprit well-intentionedly removes these giant blobs in subsequent revisions, you're still left with a huge chunk of nothing-much wasting space on your server's hard drive.

Though a long-standing item on Subversion's wishlist, there is no command that will simply obliterate files from the repository's history. Nevertheless, there is a way to achieve this. Here's how.

The first step of the process is to determine which files need to go. (Some snippets in the following are derived from StackOverflow and Christosoft blog.) First …

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