Linux
Linux Mint (Cinnamon) Not Showing Programs on Task Bar.
· β˜• 1 min read
For some strange reason, my Linux Mint Cinnamon desktop suddenly stopped showing the running program buttons on the task bar. I could only switch between running programs with ALT+TAB. It’s easy when you know how, but for those who don’t, this is what you do: Right click on the blank task bar. Select the “Add to Panel…” option. (Or similar depending on your version of Mint.) Type “Window” into the search box.

Thunderbird - Message Filters stop Working on Email Download - But Work Ok Manually.
· β˜• 2 min read
I think this topic has the longest title of all my postings! Never mind. Have you ever started Thunderbird fetching your emails, and encountered a pop-up message that starts off by saying “The message could not be filtered for folder ‘whatever’ because writing to folder failed”? Read on for the cure. Credit: go here - https://bugzilla.mozilla.org/show_bug.cgi?id=931303 - then scroll down to Comment 39. A gentleman by the name of Craig Lassen deserves all the kudos for this fix.

VirtualBox - Sending Special Key Combinations to the Guest OS.
· β˜• 1 min read
As standard, VirtualBox has a menu option (machine->Insert CTRL+ALT+Backspace or Insert CTRL+ALT+DEL) which is fine if you need these key combinations sending to the guest and not grabbed by the host, however, how can you send CTRL+ALT+F1 through CTRL+ALT+F8 to a Linux guest OS to get it to startup one of its virtual consoles? Normally, those keys would be grabbed and actioned by the host OS rather than being passed to the guest.

Beginner's Guide to Arch Linux on the Raspberry Pi - Part 2
· β˜• 8 min read
Continuing with the setting up and such like, using Arch Linux on the Raspberry Pi. This is the second blog post on the subject. In the previous posting, we managed to set up our locales, languages, keyboards, and so on. We have internet connection vie a wired Ethernet connection using either a dynamic IP address or a Static one. Time to move on. As before, if you see a command with a ‘>’ prompt it means that you should be in the root user, or have prefixed the command with sudo.

Beginner's Guide to Arch Linux on the Raspberry Pi
· β˜• 10 min read
The ARCH Linus distro for the Raspberry Pi is not the normal one used by the masses, but the benefits of ARCH are good in that it is a rolling release distro. That means, you never have to reinstall it to be on the latest version. The information that follows assumes that you have installed ARCH from the NOOBS installer. The latest version of ARCH has changed the networking system in use.

NOOBS For Raspberry Pi
· β˜• 16 min read
Updated 11th January 2015 to document NOOBS 1.3.11. NOOBS is the latest user friendly installation system from the Raspberry Pi. It allows you the ability to choose one of 7 (currently) Operating Systems to run on your Pi and a separate data partition to save your possibly shared data. You can pick and choose and change your OS at any time you wish simply by rebooting and holding the SHIFT key down.

Need to Compile a 32 bit Application on a 64 bit Linux System?
· β˜• 3 min read
I have a small utility, written in C, that I need to use from time to time. I wrote it back in 2009 when 32 bit systems were all the rage. It reads a certain type of data file and outputs lots of, ahem, interesting information about the contents. When I compiled it on my 64 bit laptop, it produced complete and utter rubbish! How did I fix it? The data file that the utility reads is a Firebird database file which has a number of long fields in various structs.

Statspack Snapshot Fails ORA-01400 Cannot Insert NULL ...
· β˜• 3 min read
Oh hum. An 11.2.0.3 Enterprise Edition production database has statspack taking a regular snapshot under the control of a dbms_scheduler job. For no apparent reason, the snapshot started failing with ORA-01400 Cannot insert NULL into PERFSTAT.STATS$SYSTEM_EVENT.EVENT. This was an interesting one to fix. The following is the investigative process, in brief. Test the snapshot process with a manual one - same error. Google and My Oracle Support aka MOS, were no help whatsoever.

Ever deleted a Data File From a Running Database?
· β˜• 1 min read
http://jarneil.wordpress.com/2013/04/23/recovering-from-rm-rf-on-a-datafile/ has all you need to know to help avert a total disaster. Tanel Poder, who knows these things, advises that the file should be quiesced or made read only before attempting the recovery.

Firefox Running Extremely Slowly?
· β˜• 1 min read
Firefox starts off ok, but soon starts running slower and slower, until it eventually starts to time out on connecting to some pages. The error messages is “the server took too long to respond” however, Firefox might be telling porkies. If you attempt to access the same URL in Opera, Chrome or, if you must, Internet Explorer, you may find that it is responding quite happily and speedily, while another try in Firefox takes ages to connect or fail again.

Linux Command to Retrieve Hardware Serial Numbers etc
· β˜• 3 min read
Ever needed to obtain the serial number (or other details) for a remote server? Couldn’t be bothered to walk/run/drive/fly all the way there just to read a sticky label on the back or bottom of said server? Read on then. The command you want to run, as root, is dmidecode. For example, to get the make and model and serial number of a server, do this: 1 dmidecode -t system The result will be similar to:

Setting Oracle Environment in Scripts
· β˜• 1 min read
A quickie! How do you set the correct Oracle environment in scripts? Do you hard code? You’d better not. I’ve lost count of the times I’ve ended up with, for example, a 10g database running with bits of the 9i software hanging around. It leads to monumental problems that can be hard to track down. Moral: Do not hard code Oracle environment details. This is what I usually do: 1 2 3 4 5 6 7 8 #!

Rsync - To Slash or Not To Slash?
· β˜• 2 min read
Rsync is great for making sure that a destination directory is synchronised with a source directory. However, do you add a slash to the source and/or destination directory names, or do you not? The answer is, it depends. Without a slash on the source directory means copy both the source directory, and the contents (recursively if specified) to the destination directory while adding a trailing slash means only copy the contents of the source directory, recursively if specified, to the destination.