Steps for fixing Macbook Pro issues:

Macbook HardDisk Repair/Format:
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a) Create the bootable USB drive with Yosemite

(i) Format the USB drive with GUID Partition
(ii) Download Yosemite from AppStore and quit the installer.
(iii) Type the below command on MacOS Terminal

sudo /Applications/Install\ OS\ X\ Yosemite.app/Contents/Resources/createinstallmedia --volume /Volumes/Untitled --applicationpath /Applications/Install\ OS\ X\ Yosemite.app --nointeraction

b) Restart the Macbook and boot from USB Drive    

    (i) Hold down the Option key while rebooting
    (ii) Click on the USB drive icon to boot

    or ( Boot using Command + S , and then select USB as “Startup Disk” )


c) Format / Repair Disk the main HDD




Battery Repair ( Resetting the System Management Controller - SMC )
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a) Shutdown the Macbook
b) Unplug the Power Cable
c) Remove the battery from Macbook , wait for 1 minute
d) Tap and hold the power on button for 5 seconds
e) Connect the battery back to Macbook
f) Reconnect the Power Cable and restart





Fix for trouble logging into MacOS:
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Steps:
(a) Hold Command + s and press Power On key
(b) #root: /sbin/mount -uw /
(c) #root: chmod 775 /
(d) #root: logout
(e) Hold Command + v while restarting





How To Reset PRAM:
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Step 1: Turn off your Mac. No need to remove the battery or detaching the power chord.

Step 2: Turn on your Mac and hold down the Command+Option+P+R keys, all at the same time.

Step 3: Hold down all four keys until you hear the startup sound twice.

The startup sound for the second time means you’ve reset the PRAM.







How To Reset SMC:
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(a) For MacBooks With Removable Battery
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Step 1: Shut down the Mac, remove the back plate and disconnect the battery.

Step 2: Press and hold the power button for five seconds before releasing.

Step 3: Connect the battery and turn the Mac back on.



(b) For MacBooks Without Removable Battery
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Step 1: Shut down the Mac and make sure it is plugged in to a power source.

Step 2: When the Mac is off, press and hold Shift+Control+Option keys as well as the Power button.

Step 3: Release all four keys at the same time. The Mac should not power on during this time.

Step 4: Press the power button to turn the Mac back on.