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#812: Real Time HD I/O, How to Reset an iOS Device, Keep Private Data Private


Well, it was nice while it lasted! Last week we saw temperatures in the high 70s and low 80s, which was a great way to start out the spring. This week, we’re back down to low 50s and rainy damp weather, as if to remind us all, “It’s not summer yet.” Oh well, Angry Birds Space came out last week, so at least I have something to do inside.

Something else to do this week—come up with ways to prank your friends for April Fool’s Day! Two possibilities are Duuuude! to make someone think their car was damaged, or iPhoneception to install random strangeness on someone’s iPhone. Sadly, April 1st falls on a Sunday this year, so the number of office pranks will be down. Keep the date in mind this Sunday when you’re surfing the web, as there are lots of websites that will try to fool you.

This week, we feature articles that are not jokes: how to tell what’s going on with your hard drive data, how to reset your iOS device, and some points to ponder on privacy. Also, a correction: last week, we published an article about the de-lamination that can sometimes occur on a MacBook unibody system. The article was accidentally attributed to Lonnie Isham; in fact it was written by Lance Putnam. Sorry, Lance!

Thanks for reading!


  Real Time HD I/O  

Do you want to see the input and output of your hard drive in real time? Do you want to see what applications are reading from and writing to your drive and vice versa?

Dynamic Tracing, or DTrace, is a suite of scripts and frameworks created by Sun Microsystems for troubleshooting. DTrace is supported on Sun’s Solaris platform and has been ported to FreeBSD (upon which OS X is based) and NetBSD. Apple added DTrace support in OS X 10.5 Leopard as part of Xcode’s Instruments development tool.

DTrace is a collection of many different tools and commands that can be run in Terminal to examine just what your computer is doing. One of the DTrace tools is the iosnoop. This is a command that must be run as root, so you’ll need to use sudo to execute it. The command gives you a live readout of your hard drive’s I/O. Each line of output in iosnoop is a system call regarding I/O to your hard drive.

501 9152 W 232493176 4096 PubSubAgent Database.sqlite3-journal
501 8967 W 232493176 4096 TextEdit TextEdit Document.rtf
501 8967 W 232493184 4096 TextEdit ??/Autosave Information/.dat2307.020
501 9153 W 232493192 4096 PreferenceSyncC ??/Preferences/
501 9153 R 45546264 8192 PreferenceSyncC ??/Preferences/
501 9153 R 45546280 8192 PreferenceSyncC ??/Preferences/
501 9153 R 45546296 8192 PreferenceSyncC ??/Preferences/
501 9153 R 25427968 4096 PreferenceSyncC ??/Preferences/
501 9153 W 1416 4096 PreferenceSyncC ??/unknown (NULL v_parent)
501 9153 W 6216 4096 PreferenceSyncC ??/unknown (NULL v_parent)
501 9153 W 6544 4096 PreferenceSyncC ??/unknown (NULL v_parent)
501 9153 W 6560 4096 PreferenceSyncC ??/unknown (NULL v_parent)

(Your output will look different. Our example has been edited so it displays properly.)

In the output above, iosnoop has listed the UID (user ID) who made the call; user 501 (me) has been executing the system I/O calls.

The second column, PID (Process ID), is a unique number provided to each application or routine that the system is performing. The PIDs grow sequentially; as a Process is terminated, it will disappear from the system but it will not give up its number until the system restarts.

The D column references what direction the data was going: R for read events, W for write.

Block refers to the location on the hard drive where the read or write function occurred, and Size is the amount of data in bytes.

COMM is the process name; for each line with a matching PID, COMM will be the same. In the above output, PubSubAgent, TextEdit and PreferenceSyncC were the only processes I captured.

Finally, PATHNAME is the directory path where the data was written to or read from.

  How to Reset an iOS Device  

I often have customers report that their iPad, iPhone, or iPod touch is not working properly. Some common issues are freezing, slow performance, graphic distortion, or the device will not power on at all, even after a full night’s charge.

When this happens, the first thing that you will want to try is a hard reset. To perform a hard reset, hold down the home button and the power button (at the top of the device) simultaneously for about 10-15 seconds. The screen will go blank; when the Apple logo appears you can let go of the two buttons.

Wait for the device to restart; this may take several minutes. Once it comes back up, test out your apps again. In a lot of cases, this will bring it “back to life.” For you old time PC users, this is the equivalent of Ctrl-Alt-Del.

Keep in mind that this reset will not delete any apps or data; it simply clears out RAM and reboots the unit. Before stopping by the store with your device, it may be worth trying out this quick and easy reset to save you a trip.

Want more helpful tips? Check out our Info page.

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