Bugs & Fixes: Re-running on empty

Like a bacterial infection that an antibiotic doesn’t entirely kill, a computer issue can come back to bite you despite you applying what seemed to be a successful solution.

Case in point: Back in November, I posted an article (Running on Empty) where I described how my friend’s iMac had bogged down to such an extent that she could not get any work done. Beyond the overall slowness, she could not save files or send email. I eventually tracked down the cause—her hard drive was completely full: zero GB available. The quick solution was to delete about 10GB of unneeded files. All was good.

It was an easy fix. But I remained uneasy. I knew that my friend placed minimal demands on her iMac. About all she used it for was web browsing, email, and photos. I doubted that she had actually filled up her hard drive just on these activities.

My guess was that there was something else going on; something behind the scenes was eating up her drive space. If I was right, I expected that I would be hearing from her again.

I was right. After a few weeks, she once again found herself with zero GB available. She could get work done by periodically restarting the Mac; this cleared out enough temporary files to give her room to breathe. But this was neither a convenient nor a permanent fix.

It was time to take a closer look at this symptom. I began a search of all the folders on her drive, checking their size. There are utilities that can help with this task, but I decided to use the Finder. Before commencing the search, I made all invisible files visible. Again, there are numerous freeware utilities that can do this. I made the change so I could check the normally invisible UNIX directories (which is where I expected the culprit was hiding). Sure enough, I eventually identified a folder named asl, located in the /var/log directory. Inside that folder were over 1,000 items (!) that were taking up over 32GB (!!).

Initially, I was unsure what these files were or whether they were safe to delete. So I did what I always do when confronted with the unknown: searched the web for answers. I quickly found several sites that delved into the matter. The consensus was that these were log files (Apple System Log, asl, to be precise) generated by Mac OS X. As such, they could be safely deleted (although it would probably be best to save the most recent files). I was able to delete the files simply by dragging them to the Trash. I emptied the Trash and voilà, 32GB of free disk space.

Normally, this sort of log file build up should not occur. Mac OS X should delete older log files, as it generates new ones. Clearly, this was not happening. From what I have read, this is due to a bug that first appeared in OS X 10.5.6—when Apple changed the way these log files were managed (as covered in this MacFixIt article from 2009). The result is that the log manager may get stuck from time to time.

I assume the bug is no longer present in current versions of OS X. However, my friend is still using Mac OS X 10.5.8 (her iMac is an older PowerPC model and cannot be updated further).

Will the log build up resume? Will my friend soon run out of drive space again? I am optimistic that things are now okay. When I looked over the creation dates of the trashed log files, most were from months ago. It seemed that whatever had caused the manager to stick was now resolved. Still, I’ve told my friend to monitor her free drive space. If she starts to see a steady decline, she’ll have to delete the log files again. Otherwise, case closed.

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