How to check DNS cache status in Mac OS X

February 20, 2013 - 8:58pm - by admin

As a follow-up to How to Flush DNS Cache in Mac OS X I have received a question:

how do I know if it worked? In other words, is there a way to check if the DNS cache is cleared?

To see the DNS cache status you may run

sudo killall -INFO mDNSResponder

Thus the SIGINFO signal will dump a snapshot summary of the DNS internal state to

/var/log/system.log

Voilà :-)

 

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Print-screen (screenshots) in Mac OS X

November 12, 2012 - 9:04pm - by admin

Keyboard shortcuts

• Command-Shift-3: Take a screenshot of the screen, and save it as a file on the desktop


• Command-Shift-4, then select an area: Take a screenshot of an area and save it as a file on the desktop


• Command-Shift-4, then space, then click a window: Take a screenshot of a window and save it as a file on the desktop


• Command-Control-Shift-3: Take a screenshot of the screen, and save it to the clipboard


• Command-Control-Shift-4, then select an area: Take a screenshot of an area and save it to the clipboard


• Command-Control-Shift-4, then space, then click a window: Take a screenshot of a window and save it to the clipboard

In Leopard and later, the following keys can be held down while selecting an area (via Command-Shift-4 or Command-Control-Shift-4):

• Space, to lock the size of the selected region and instead move it when the mouse moves


• Shift, to resize only one edge of the selected region


• Option, to resize the selected region with its center as the anchor point

Formats

Different versions of Mac OS X have different formats for screenshots.

• Mac OS X 10.2 (Jaguar): jpg


• Mac OS X 10.3 (Panther): pdf


• Mac OS X 10.4 (Tiger) and later: png

In Mac OS X 10.4 and later, the default screenshot format can be changed, by opening Terminal (located at /Applications/Utilities/Terminal) and typing in:

defaults write com.apple.screencapture type image_format

killall SystemUIServer

Where image_format is one of jpg, tiff, pdf, png, bmp or pict (among others). If you omit the second line, you will need to log out and in again for the change to take effect.

Grab and Preview

Instead of using the keyboard shortcuts above, screenshots can be taken by using the Grab application included with Mac OS X. It is located at /Applications/Utilities/Grab.

In Mac OS X 10.4, the Preview application can also be used to take screenshots, by using the Grab submenu in the File menu.

From the Terminal

The screencapture command in the Terminal can also be used to capture screenshots, and is useful for scripts. Here is an example.

screencapture -iW ~/Desktop/screen.jpg

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How to Flush DNS Cache in Mac OS X

October 11, 2012 - 6:31pm - by admin

After upgrading to 10.8.2 I have got a problem with adding a new entry into hosts file: the update was recognised only after system restart. But a more easy solution was just to flash DNS cache! So,

... flushing your DNS cache in Mac OS X is actually really easy, and there are two different commands to use, one for Leopard and for Tiger. Depending on your version of OS X, open your Terminal and follow the appropriate directions below:

Flushing DNS Cache in OS X Lion (10.7) and OS X Mountain Lion (10.8)

Launch Terminal and enter the following command, you will need to enter an administrative password:

sudo killall -HUP mDNSResponder

Note the dscacheutil still exists in 10.7 and 10.8, but the official method to clear out DNS caches is through killing mDNSResponder. You can also find that process running in Activity Monitor.

Flush DNS Cache in Mac OS X 10.5, Mac OS X 10.6

Launch Terminal and issue the following command:

dscacheutil -flushcache

All done, your DNS has been flushed. On a side note, the dscacheutil is interesting in general and worth taking a look at, try the -statistics flag instead for some stats.

Flush your DNS Cache in Mac OS X 10.4 Tiger

Type the following command in the Terminal:

lookupd -flushcache

That’s it - now your DNS settings should be as you intended them to be :-)

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