MacOSG: fsck your hard drive periodically
Posted by Dennis Sellers 
Nov 17, 2006 at 4:29pm
By Dave Merten
One thing I always have believed in when it comes to maintaining a Mac, is preventive maintenance. One important part of that, is maintaining a healthy hard drive. One way to do that, is to periodically run Disk First Aid to check the integrity of your drive. Another way to do it, is run fsck. What is fsck? fsck stands for “file system consistency check,” and is a “built-in” command-line utility for verifying and repairing your hard drive.
So why not just use Disk First Aid? Well, in some situations, file system errors can prevent your computer from starting up, or reaching the login screen. Also, it may reach the login screen, but not load the Desktop after you log in. These issues can occur after an improper shutdown, forced restart, or power interruption. Also, you may run into a situation where you’re on the road and don’t have your install disc handy to boot from and run Disk First Aid.
To run fsck, you need to boot into Single-User mode.
1. Shut down the computer if it is on.
2. Press the power button to start the computer.
3. Immediately press and hold the Command-S key.
Next, at the command-line prompt, type in the following:
/sbin/fsck -fy
Then press Return. fsck will go through five “phases” and then return information about your disk. If there is a problem, it will automatically repair it and give you a summary of the damage.
So how often should you run fsck? Personally, I always run it after an improper shutdown, forced restart, or power interruption, as stated above. Any of these situations can cause file system problems, so why not eliminate any right away? It only takes a couple of minutes and may save you headaches down the road. It also wouldn’t hurt to run it whenever you do your periodic system maintenance.
The Mac Owners Support Group, aka MacOSG, was conceived in February, 2004 as the G5 Owners Support Group by Dave Merten, a former “Focus on Mac Support” guide at About.com. After purchasing a DOA Power Mac G5, and noticing on Apple Discussion Boards that people seemed to be having a lot of common hardware problems with them, Merten decided to open a support site for Power Mac G5 owners. He called it G5 Owners Support Group, registered the G5support.com domain and also applied to Apple to become an online Apple User Group.
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Ken Says:
Also note that if you’re using HFS+ with Journaling (which, I believe, is the default option when initializing hard drives), the need for fsck is greatly reduced. The whole point of a journaling file system is to guard against corruption from power failures.
http://docs.info.apple.com/article.html?artnum=107249
While there’s probably no harm in running fsck every now and then, it seems like an unnecessary procedure for most people.
Posted on November 17, 2006
Dave Merten Says:
Rainy Day Wrote:
“Why not? Well, because the system will automatically run fsck on boot-up anyhow, and do repairs if required, that’s why.”
It can’t go through the thorough five “phases” check. When I run fsck, It takes 1 minute and 50 seconds to go through the five “phases,” and that’s just to check the drive. My computer boots to the desktop in under 30 seconds.
We had a brown out here the other day and my computer had restarted itself when the power came back on. When I got home, I decided to run fsck and it found a whole list of problems. In fact, I had to run fsck 2x to repair everything.
I don’t know about you, but when it comes to all my data, I’ll spend a few minutes running fsck to head off any potential problems that could end up causing a catastrophic hard drive failure. I strongly believe in preventive maintenance.
Posted on November 18, 2006
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Dennis Sellers
Dennis has been a newspaper editor/reporter (seven years) and teacher (seven years). He has over 4,000 magazine, newspaper and online articles to his credit. He has also covered the Mac and tech industries for over a decade for such online publications as MacCentral, MacMinute and now MacsimumNews.
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Rainy Day Says:
“So how often should you run fsck? Personally, I always run it after an improper shutdown, forced restart, or power interruption, as stated above. Any of these situations can cause file system problems, so why not eliminate any right away?”
Why not? Well, because the system will automatically run fsck on boot-up anyhow, and do repairs if required, that’s why.
The only time running fsck manually might be advantageous is when the disk has been screwed up so badly that the automatic run can’t fix it by itself. Sometimes it simply takes multiple passes of fsck to fully fix a problem. Fortunately, these times are relatively rare.
By the way, Disk First Aid is now called Disk Utility. Disk Utility is basically a GUI for fsck.
Btw: You don’t actually need to be in single user mode to run fsck, however certain operations may be easier if you are (as you don’t need to know as much about Unix filesystem operation). However if all you want to do is verify a disk is in good shape, you can easily do so in multi-user mode, or by running Disk Utility during a normal boot. If either report that the disk is good, there is absolutely no value in booting into single user mode (or off CD) as you’ll get the same thumbs-up there too. It is only disk repairs which get tricky when in multi-user mode.
Posted on November 17, 2006