So these are two commands to mount shared folder in a linux host on a linux guest so that the guest has full permission in the shared folders.

This first command should be executed on the guest VM

sudo mount -t vboxsf SHARE_NAME /MOUNT_POINT/ -o rw,users,umask=0000

VBoxManage setextradata VM_NAME VBoxInternal2/SharedFoldersEnableSymlinksCreate/SHARE_NAME 1 

I have recently been messing around with a raspberry pi at work (a Pi2 model B) for driving display screens for our In-Venue product of which I am the product owner. And very exciting it is too, because the real world is the new frontier (this pdf is also a good primer). If you see what I mean, but more on that another time.

So.. I had to overclock the Pi to improve browser performance to even get near to acceptable speed and smoothness of animations. Pro Tip, the Pi is not a graphics device! Having done this and got acceptable results for a clunky prototype to demo with, and load averages that stayed on the sane side of normal I thought I'd better see if I was frying the CPU. And because I will inevitably forget this useful command I'm saving it here for posterity. Here's how I got the temperature reading..

/opt/vc/bin/vcgencmd measure_temp

I tried to install a couple of updates on my work laptop, running Ubuntu 12.04, a minute or two ago when prompted by the update manager, and I got the "requires installation of untrusted packages" error. I've since dicovered that there are two ways round this, one is to allow untrusted packages by doing the update as root or via sudo, and saying "y" when asked

Install these packages without verification [y/N]?

sudo apt-get clean
cd /var/lib/apt
sudo mv lists lists.old
sudo mkdir -p lists/partial
sudo apt-get clean 
sudo apt-get update

I spent a while figuring out how to get a list of email recipient addresses from the maillog, without duplicates, for a specific day on RHEL. In the end I distilled it into to one line.

I'm sure I will have to do it again, so I'm making a note of it here, meantime if you need to extract recipient addresses from maillog you're welcome to try it. just paste it onto the command line and hit the go button, its surpisingly quick.

cat /var/log/maillog | grep "Oct 19" |\
grep to= |cut -f5 -d":" | cut -f2 -d"=" | cut -f1 -d"," | \
sed 's/<//' | sed 's/>//' | \
sort | uniq > addresses.txt