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In order to do this, shut down your Mac, then start it up again while holding down the Command, Option, P and R keys.Wait until you hear the startup chime twice, then release the keys and allow normal startup to proceed.However, there are several alternative, manual ways to check for and fix hard-drive errors. This is the standard and recommended method for checking the system's hard drive, since the graphical interface is quick and intuitive to use.Simply select your boot volume in the device list (this will be the name of your boot drive), and then hold the Option, Command, or Shift key and select the drive device itself, which will have the size and manufacturer in its name.Unfortunately, formatting errors can happen even if you've just been using your computer in a normal way, so even though your system may be running fine at the moment, it can only benefit from a regular drive check.
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Two options for use in the Terminal are the "diskutil" command, and the "fsck" command.
Both of these can be used to check the hard drive for errors, using the following syntax: diskutil verify Disk DRIVEID diskutil verify Volume VOLUME In these commands, DRIVEID is the device ID of your boot disk, which usually is "disk0," but may be another value such as "disk1" or another number if you have multiple physical drives in your system.
The final option is to use the "fsck" routine, which is similar to the diskutil command and runs the same checking routines, but is a little barer.
Apple recommends using diskutil whenever possible, but sometimes diskutil may show an error it cannot overcome, in which case fsck may be successful.