Some times my mac not getting shut down, some times my mac not getting shut down

Question

some times my mac not getting shut down, some times my mac not getting shut down
it will show white scree for long time and will not shut down

Answer 1

Launch the Console application in any of the following ways:
☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)
☞ In the Finder, press the key combination shift-command-U. The application is in the folder that opens.
☞ If you’re running Mac OS X 10.7 or later, open LaunchPad. Click Utilities, then Console in the page that opens.
Step 1
Select "system.log" from the file list. Enter "BOOT_TIME" (without the quotes) in the search box. Note the times of the log messages referring to boot times. Now clear the search box and scroll back in the log to the time of the most recent boot when you had the problem. Post the messages logged during the time when you had the problem – the text, please, not a screenshot. For example, if the problem is a slow startup taking three minutes, post the messages timestamped within three minutes after the boot time. If the problem is a crash or a shutdown hang, post the messages from before the boot time, when the system was about to crash or was failing to shut down.
Edit out excessive repeats and personal information, if any.
If the log doesn't go back far enough in time, scroll down in the Console file list to /private/var/log/system.log.0.bz2. Search the archived log, and if necessary the older ones below them, for the same information.
Step 2
Do the same with kernel.log.
Step 3
Still in Console, look under System Diagnostic Reports for crash or panic logs, and post the most recent one, if any. For privacy’s sake, I suggest you edit out the “Anonymous UUID,” a long string of letters, numbers, and dashes in the header of the report, if present (it may not be.) Please do not post shutdownStall or hang logs – they're very long and not helpful.