Computing

Quick Links

my DNS servers Free DNS @ afraid.org OzHosting
useful lookups WhoIs database Ubuntu Python 2.7

How The Web Pages were One

These web pages have gone through a number of interations. This Web Page documents the story.

Context

I have a range of computers. Keeping track of them (and maintaining them!) can be a headache. So I've started compiling a list of current machines. There are also a number of web servers (such as the one you are reading right now on www.ajh.co@wolseley). Here is a list of the computers/servers, their URLs, DNS sites, use and model:

Server Name Use Model URL DNS
flinders Main home server Dell R900 dual processor ajh.co, ajh.id.au OzHosting
eregnans Off-site server virtual linux box ajhurst.org, cahurst.org, wiki.gwuc.org.au, glenwaverleychurches.org Afraid
dimboola General purpose system Apple iMac 27" OSX 10.6.8 - -
wolseley General purpose system HP Compaq Ubuntu 13.10 - -
bittern laptop Apple MacBook Pro OSX 10.6.8 - -
garedelyon house computer Vortex86SX minibox Debian 3.1 - -
montparnasse spare house computer Vortex86SX minibox Debian 3.1 - -
dimboola
my home desktop iMac: dimboola.ajh.id.au
eregnans
my RackSpace virtual Linux box (Ubuntu): eregnans.ajhurst.org, wiki.gwuc.org.au (church wiki server only)
bittern
my laptop

Hints and Fixes

Mail Folder Sort Order not maintained

My (Mac OSX) mail folders suddenly started being displayed in non-alpha order whenever I added a new folder. I'm not the only person to notice this - there is an Apple Disscussion Thread on it. The original page is available, but in case it disappears, I've saved a copy.

Invisible files

When I first obtained a Mac, using (IIRC) Mac OS 3.1 or thereabouts, my son discovered that there was a resource fork bit that made files invisible. He delighted in changing that bit on files that I used, so I rapidly discovered how to unset it again. That facility is still there in OS X, so I have documented that little lurk to avoid any future mischief.

To make a file invisible:

$ /Developer/Tools/SetFile -a V file-name

(upper case V)

To make a file visible:

$ /Developer/Tools/SetFile -a v file-name

(lower case v)

Safari Plug-Ins

I installed/updated my Adobe reader, and the next time I used Safari, it asked me if I wanted to install the Adobe plug-in to make Safari use the Adobe reader for PDF files. I said yes at the time, but after a bit of use, found it too slow. Granted, it does have more features, but not the one I wanted, which was to open it up outside the browser. With the standard Preview option, this was just a right-mouse pull down "Open in Preview", very convenient. But how to get back to Preview?

A bit of Googling revealed the answer. In Tiger (10.4) and Leopard (10.5), there is a folder /Library/Internet Plug-Ins/ that contains all the plug-ins. Remove the one called AdobePDFViewer.plugin, restart Safari, and you are back with Preview.

And while on the subject of Safari, here's how to change the default browser preference:

  1. Open Safari (/Applications).
  2. From the Safari menu, choose Preferences.
  3. Click the General button.
  4. Choose a different browser from the Default Web Browser pop-up menu.
(from http://support.apple.com/kb/HT1637)

Time Machine Repair

A colleague had difficulties recovering his Time Machine backups when he had his motherboard replaced, and he sent me this URL about a fix. It seemed like good insurance to add it to this page: http://www.macosxhints.com/article.php?story=20080128003716101

OpenOffice recovery documents

When Open Office (version 3) "loses" its recovery files, and keeps asking to recover (non-existent) files, edit the file: /Users/ajh/Library/ApplicationSupport/OpenOffice.org/3/user/registry/data/org/openoffice/Office/Recovery.xcu to delete the element nodes containing the offending file path. Then save this file, and restart OpenOffice.

Finding out the screen resolution

I run a number of different displays, and when starting up various programs I need to know the current screen resolution. This little script does the trick:

        #!/bin/bash
        #
        # screenres      determine screen resolution 'HEIGHTxWIDTH'
        # screenres -w   determine screen resolution 'WIDTH'
        # screenres -h   determine screen resolution 'HEIGHT'
        # 
        res=`xdpyinfo | awk '/dimensions/ {print $2}'`
        if [ "$1" = '-h' ] ; then
          # extract height and print
          expr "$res" : '.*x\([0-9]*\)'
        elif [ "$1" = '-w' ] ; then
          # extract width and print
          expr "$res" : '\([0-9]*\)'
        else
          # print full resolution
          echo $res
        fi
      

Apple's X11 Cut and Paste

Apple did a Great Thing in making X11 available as part of OS X, but it was always going to be a difficult task, given the different "look and feel" of the two user interfaces. To try and fix the inconsistency between the OS X cut and paste, and X11's cut and paste, check out this Fix for Apple's X11 Cut and Paste

Keyboard Shortcuts on Booting

To find out all those nifty keyboard things when things go wrong, here's a page to describe the Keyboard Startup Shortcuts.

Automatically changing the Desktop Picture in Snow Leopard

I had a cool little script that changed the desktop background picture (aka wallpaper) automatically, according to parameters stored in an XML file. See this Multithreaded Image Viewer for details. Most of it was pretty plain python programming (I even set it as an exercise in concurrent programming one year), but it relied upon a shell script setBackground.sh that used an Applescript script to do the actual picture change via a set desktop picture to file MyPicFile.

Here's what that script looks like:

      #!/bin/sh
      #
      # simple shell script to set the backgroup image
      # uses an Applescript call to do the actual work
      # call:
      #  setBackground.sh <imageFilename>
      
      FILE=$1
      
      #echo $FILE >>output.txt
      
      /usr/bin/osascript <<END
      tell application "Finder"
        set myFile to POSIX file "$FILE" as string
        set desktop picture to file myFile
      end tell
      END
    

But then it broke in Snow Leopard, for reasons I do not understand. Attempts to find how to do this task via much Googling also proved fruitless. While fiddling around with the standard Apple Change Desktop Background pop-up memu, I hit on the idea of having a folder with only one image in it, and setting the reload time to 5 seconds, the shortest reload time.

Hence this new script for setBackground.sh. It looks like this:

      #!/bin/sh
      FOLDER=/Users/ajh/Pictures/Desktop
      FILE=$1
      
      rm $FOLDER/*
      ln -s $FILE $FOLDER
    

I used a soft link without thinking about why. It could be a hard link, I guess.

(20100330:094441) And this is not perfect by any means. It breaks on my laptop when I put it to sleep, or change locations, or both, or neither (hard to say which, since it seems very erratic!) Every so often I have to invoke "Change Desktop Background", and reselect the folder in which the temporary item is placed.

(20101216:160200) The behaviour in Snow Leopard is now consistent with Leopard again. I don't know what happened, but I now use the script identified at the beginning of this item. I'm keeping the rest of the story here just in case.

Filename extensions

I noticed while using Keynote that my filename extensions were getting thrown away. I was not the only one to be puzzled by this behaviour, so I thought I should comment on the fix required.

Go to the Finder Preferences, and click the Advanced tab. Under Snow Leopard, the top check box should be "Show all filename extensions". If this is unchecked, click it, and your filename extensions will magically reappear!

For some reason, Apple appears to have changed the default value on this from Leopard to Snow Leopard, leaving many users puzzled as to what is going on.

Fixing the X11 "Focus Follows Mouse" hassle

In a terminal, type:

    defaults write org.x.X11 wm_ffm -bool true
and then restart X11.

Unix Stuff

To set the system timezone to Melbourne

      $ sudo bash
      $ cd /etc
      $ ln -sf /usr/share/zoneinfo/Australia/Melbourne localtime
    

Moving to Ubuntu

I got the irrits with Apple and have sworn not to buy a new system or upgrade the systems I have, preferring instead to move (back) to Linux as necessity demands. But Ubuntu has its own irrits, too! This is a log of things that I have fixed.

Virtual desktops

Mac OSX calls them "Spaces", Ubuntu calls them "Workspaces". I prefer "Virtual Desktops". Oh well. You can't please everyone.

The hassle is that there is no clear way of driving the number of them, and how to switch between them.

Setting Up
Go into the System Settings > Appearance > Behaviour, and check the box "Enable workspaces". This sets up the default 2x2 workspaces.
Changing the Number of Workspaces
Make sure that "CompizConfig Settings Manager" is installed (use the "Ubuntu Software Centre" to search for and install this). Then follow General Options > Desktop Size, and set the Horizontal Virtual Size and Vertical Virtual Size to your preferences. Close the CCSM.
Showing the Virtual Desktops
You show see an icon in the launcher that looks like this one (it may have a background colour to match the launcher). If you click this icon, a representation of the workspaces available will be shown. Click it again to dismiss, or click inside any of the workspaces to switch to that workspace.

Keyboard Shortcut to Switch Workspace
CTRL-ALT-arrow will change to the next workspace in the direction of arrow.
This page maintained by John Hurst.
Copyright Monash University Acceptable Use Policy
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30 Jan 2014
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