chmod is the tool to change the permission on UNIX based systems.

For the options consult wikipedia.

Why is it worth to mention it here? If you change the permissions recusively ofer a directory tree, usually you do not have the right permissions for directories and for regular files.

You can avoid that by using find, as shown in the example:

find . -type d -print | xargs chmod 755

find . -type f -print | xargs chmod 644

Type “d” applies the change to directories, whereas type “f” applies it to files. find “.” means to all files starting in the current directory.

Activate the tftp server on your Mac. It works on Leopard and Snow Leopard:

To change the properties, edit the file

/System/Library/LaunchDaemons/tftp.plist

The default directory is /private/tftpboot.

Make this directory accessible for everybody.

chmod 777 /private/tftpboot

and start it with

sudo launchctl load -F /System/Library/LaunchDaemons/tftp.plist

If you want to stop the daemon, do

sudo launchctl unload /System/Library/LaunchDaemons/tftp.plist

Keep one of these keys pressed at system start.

	Eject the inserted CD/DVD
	Boots from a CD/DVD with a system image
	Boots from the first HD partition
	Boots from the network (netboot)
	Enforces a screen reset
	Boots in firewire target mode
	Boots in safe mode. Disables login items and less important kernel files
	Boots in verbose mode
	Boots in single-user mode. Goes directly into command-line

Users coming from the UNIX side are used to a life without anti virus scanner. Microsoft users feel uncomfortable and naked, if they don’t have a virus scanner. This discrepancy always leeds to discussions about the need of an antivirus scanner on an Apple computer. If you ask the AV industrie, they say you need one. Of course, there is a lot of money to make in this market. Experience shows, today you do not really need one.

Currently there are three known trojans for Mac available. One of them only installs, if you get a cracked verison of iWork 09. Even checking the signature list of an antivirus company only gives you a short list. Being a little bit careful from where you download your software helps more then spending a lot of money for software, which just slows down your machine.

Starting with 10.6 Apple started to scan downloads for trojans. There is a file called /System/Library/CoreServices/CoreTypes.bundle/Contents/Resources/XProtect.plist on your Mac containing the signatures of these three known trojans.

Anyway. Currently it is not necessary to spend a lot of money for virus protection on a Mac. If you want to scan your Mac from time to time, get the open source antivirus scanner clamav, with comes nicely packed with a nice frontend in a package called ClamXav. Download the free version and scan your Mac from time to time.

Safari 4 automatically stores previews from the sites you vist. If you do not like this feature and want to turn it off, do:

Open a Terminal and enter

defaults write com.apple.Safari DebugSnapshotsUpdatePolicy -int 2
rm "Library/Caches/com.apple.Safari/Webpage Previews/*"

Quit Safari and relaunch it.

To turn it back on, do:

defaults write com.apple.Safari DebugSnapshotsUpdatePolicy