Cables. Who cares?

A few days ago I was struggling with a desktop multifunction Samsung printer.

Everything was fine except, the scanner.

The MFP was hooked up to a PC with a USB cable.
Whenever I tried to scan a document, an error panel appeard saying Hardware I/0 error.
I removed and downloaded the latest drivers from Samsung support site without luck.

Changing the USB cable with a new, good shielded, not too long one, removed the impediment.

PowerMac G5 DP using one processor

Suddenly a PowerMac G5 Dual Processor started having kernel panic after a few minutes from start up.

It turned out that one of the two processors was faulty.

A Google search reported that in a DP PowerMac, if the first processor is damaged, usually the computer does not even boot up.

While, if it is the second, it shows the behavior I experienced.

I was able to circumvent the problem leaving the processor in its place.

To do so, you must enter Open Firmware.
Immediately after the startup sound, press and hold the key combination Command-Option-O-F
Release the keys when you see a white screen that says "Welcome to Open Firmware."

At the prompt type

setenv boot-args cpus=1

and hit return. If the syntax was correct you got an OK result.
Now type

mac-boot

hit return and the operating system boots.
I tested the reliability of the new mono PowerMac :-) by running Grapher, find the program inside Utilities folder, with a few windows drawing 3D animations for more than two hours and no crash at all.

Beware! Reissue the Open Firmware procedure if you reset PRAM

Backup strategy with rsync

Everyone knows backups are important.
But usually everybody doesn't care much about them until an unrecoverable event happens.
So, why wait for that very moment, if, with a little bit of effort, you can have a rock solid data backup strategy.

A very good review on how to use the standard *nix rsync program to backup your valued electronic data.

Easy Automated Snapshot-Style Backups with Linux and Rsync

Mac OS X print presets

Let's say you have a color laser printer installed in your system but you usually print in black and white.
It is very likely that the printer presets are in color.
So, every time you need to print a document, and you need it B/W, you have to go through the printer settings and choose the appropriate parameters.
That could eventually become annoying.
Yes, it is possible to create one or more personalized presets to choose from, before hitting the Print button, but that is not always the perfect solution.
There are programs, i.e. the MS Office suite, that have a nice little button with a printer, which sends the document directly to the print queue, bypassing the print dialogue screen.

If you want to modify the "Standard" presets there is a straightforward solution. Just fire up your browser and fill the URL bar with the address below or just click the link

http://localhost:631

It'll be presented the CUPS (Common UNIX Printing System) page. From there, you can change whatever you want regarding the printer or printers settings that will became the new defaults.

VNC screen scrambled

Many Apple servers out there are headless. That is particularly true for the ones before the advent of the Xserve with Intel processor.
And quite often, servers are managed remotely using software like the multitude of VNC server (GPL) or Apple Remote Desktop (commercial).

I personally choose Vine Server OSX Vnc to control a couple of Xserve. One with Panther server and the other one with Tiger server. This program has the advantage to handle international keyboard layout over the VNC server self contained in Tiger which can't.

I think I played around with Monitor Preferences because at some point logging into the VNC server presented a screen like this.


For some times I ended up quitting the VNC client and relaunching it again to get a comprehensible image. But that was very annoying.

So I did some internet searches and I found the solution to the problem removing the file
/Library/Preferences/com.apple.windowserver.plist
on the server side.

NT Backup and .bks file (reloaded)

The Windows program NT Backup can use a file with the extension .bks that contains the list of files or group of files to be saved.
As a matter of fact you can also use this file to exclude some files you don't want to be included into the backup set.

The syntax of the .bks file is as follows

X:\
This entire drive will be backed up.
X:\Folder_name\
Files in this folder will be backed up.
X:\Folder_name\ /exclude
Files in this folder will be excluded.
X:\File_name.ext
This file will be backed up.
X:\File_name.ext /exclude
This file will be excluded.
SystemState
The System State will be backed up.
\\Server\Share\Folder\
These network files will be backed up.

This file is normally created and managed by the program itself and it seems to be the only way to obtain a properly formatted .bks.

In fact, the .bks file is a "special" UNICODE file without the Unicode header (0xFFFE).
If you manually edit this file i.e. with NOTEPAD, the standard text editor included since the first version of Windows, and save it as a Unicode you are ruined. The scheduled backup job stop working.
It is very handy indeed to be able to manage that file as you like with your favourite text editor.
As long as you do that you need to strip the first two bytes (0xFFFE) off the .bks.

A simple way is to use a hexadecimal file editor.

Below you'll find some links to a few Hex Editor programs

Windows
Hex Editor XVI32

Mac OS X
HexEdit

Linux
Midnight Commander

Ubuntu, how to regenerate OpenSSH host keys

First, change directory to /etc/ssh

cd /etc/ssh

now, remove the old rsa and dsa keys files

sudo rm ssh_host_*

Generate new keys

sudo dpkg-reconfigure openssh-server

If you wanto to be 100% sure that the server you are connecting to is the one it claims to be, take note of the RSA and DSA fingerprint

sudo ssh-keygen -l -f ssh_host_rsa_key
sudo ssh-keygen -l -f ssh_host_dsa_key

to check against the fingerprint displayed next time you are going to connect.

Last, update your known_hosts file

~/.ssh/known_hosts

removing the line that contains the old reference, otherwise you'll get the following message

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
Someone could be eavesdropping on you right now (man-in-the-middle attack)!