How to Change the Mac Startup Disk From the Command Line

Click the magnifying glass icon at the top of the Mac screen to display the Spotlight dialog box, type 'Terminal' and then click 'Terminal' in the list of results to launch the Terminal utility.
Type 'sudo bless -mount /Volumes/Startup_Disk_Name -setBoot' without the quotation marks into the Terminal window. The Bless command changes the startup disk. Replace 'Startup_Disk_Name' with the correct name of the disk you want to boot from. If the name contains spaces, enclose the entire path in quotation marks. For example, if your startup disk is labeled 'My Mac,' type the following command: sudo bless -mount '/Volumes/My Mac' -setBoot.
Press 'Enter' to run the command and change the startup disk. Note that your Mac boots from the new disk after you restart it. To restart the Mac from the command line immediately, run the following command: sudo shutdown -r now. Don't forget to save your work before you issue the command.
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How to Block a Website From an Apple Computer

Open the 'Applications' folder. Double click 'Utilities' and 'Terminal.' A command prompt will open.
Type 'sudo nano /etc/hosts' without the quotation marks and hit 'Return.'
Enter the Administrator password for the computer. This should bring you to a text file with the words 'Host Database' at the top.
Use the arrow keys on the keyboard to move the cursor down to the bottom of the file. Type '127.0.0.1 (website)' without the quotation marks. For example, if the website that you want to block is example.com, type '127.0.0.1 www.example.com.'
Hit the 'Control' and 'O' keys on the keyboard simultaneously, then hit 'Return' to save the file. Close the terminal window. The website that you have specified is now blocked. To remove the block, return to the Host Database using the steps outlined above, and remove the line referencing that website.
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How to Clear NVRAM (5 Steps)

Click 'Start', type 'cmd' in the 'Search' box and press 'Enter'. The Command Prompt opens.
Type 'Debug' (without quotation marks) and press 'Enter'. You will see a line that reads 'C:\WINDOWS>DEBUG'.
Type each of the following commands, pressing 'Enter' after each command before proceeding to the next command.AMOV AX,0MOV AX,COUT 70,ALMOV AX,0OUT 71,ALINC CXCMP CX,100JB 103INT 20
Enter a blank line and hit 'Enter'. Type 'G' (without quotes) and hit 'Enter'. Type 'Q' (without quotes) and hit 'Enter'.
Close the Command Prompt and restart your computer.
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