OnyX User Guide
What is OnyX?
Onyx is a Mac maintenance utility developed by French developer Joël Barrière. Your Mac, like most things in life, needs to be cleaned and maintained. OnyX is the best tool for this job.
Below is a small list of some of the things that OnyX can do;
Verify the structure of the file system on the start-up volume
Repair disk permissions
Check user and system .plist syntax
Configure certain parameters that are hidden from the system and from certain applications
Empty System, User, Internet, and Font caches
Force Empty the Trash
Rebuild Launch Services
Rebuild Spotlight and Mail indexes
Should I Use OnyX?
Yes, if you understand the majority of the features listed above.
No, In short, if you do not understand the features listed above. OnyX is a very powerful tool that can solve complex problems on OS X; but, that also means it can cause damage to the machine if used incorrectly.
The best thing about this application is that it's free.
Download OnyX for OS X Yosemite here
After you have installed OnyX this will be the first thing you see
The first thing I always do, like everyone else, is read the entire software license agreement, twice. Once you are done reading and taking notes, simply uncheck the 'Display at launch' box.
Every time Onyx opens it will check the S.M.A.R.T. (Self-Monitoring, Analysis and Reporting Technology) status of your hard drive. S.M.A.R.T. is a monitoring system, included in hard drives, which detects possible indicators of hardware failures.
Next, click Maintenance > Permissions > Execute
Permissions do exactly what they sound like; they give specific permissions (who can read, write, and view) for each file. If permissions are incorrect for certain files this can cause problems when the OS tries to access them.
Next click Scrips > Execute
The daily scripts remove old/temporary file logs, the weekly scripts rebuild system databases, and the monthly scripts create usage reports and rotate specific log files.
Next click Cleaning > System > Execute
The next few steps will be cleaning cache memory files. After you do this some applications will take slightly longer to load the first time you open them, but this will only happen once.
The main purpose of cache (pronounced cash) is to store programing instructions that are frequently used so it can improve the speed of applications. For example, you keep your wallet in your pocket so when you make purchases it is easily accessible. You wouldn't keep your wallet in your car and walk from the register to your car every time that you made a purchase, right? The cache is similar to this; it keeps frequently used information on hand so applications can access it quickly.
Next click Cleaning > User > Execute
Next click Cleaning > Internet > Execute
Some of these items shown below are unchecked, but if you feel comfortable cleaning those files feel free to do so.
Next click Cleaning > Fonts > Execute
Next click Cleaning > Logs > Execute
Next click Cleaning > Misc. > Execute
Next click Cleaning > Trash > Execute
You are given two different options to empty your trash, Delete and Secure Delete, there's an important difference between the two.
First is the common Delete; this only removes the directory entry to the file. Usually, these files can be easily recovered using third party software. There is nothing wrong with deleting data this way; in fact, you may want to (considering that if you delete something by mistake, you may be able to recover it). However, if you have sensitive information, then you should use Secure Delete.
Secure Delete, unlike Delete, erases the file seven times. First it erases the files information, then writes random information over the file, erases it again, and repeats those steps seven times. This method meets the United States Department of Defense security standards.
You are now done with the maintenance features of OnyX. Feel free to explore the other tabs, Onyx has many additional features besides maintenance. Do not forget that this is a very powerful program, so be careful with the settings you change.