Invalid node structure: Could not repair volume "HD".
Those are the terrible, heart-sinking words a computer programmer never wants to see on his screen, especially when he has been living in the forest and has not backed up his data for nearly three months. Daily photos, thousands of emails, and tens of thousands of lines of source code for his new project, all allegedly lost to the criss-crossed B-Tree of the Mac OSX Catalog File, which has suddenly lost its internal map, and thereby its ability to start.
For five hours tonight my operating system was frozen, stuck on its gray loading screen as the computer fan whirred ever-louder, struggling to keep cool. I dashed back and forth between this building and the next, where there is an old and creaky PC, and scoured the depths of Mac forums, some eight years old, for hints on what to do in this particular situation. Most of these reports were hopeless, and talked about a total data loss, requiring a reformatted hard drive to bring the disk back to life. Others said the disk was destroyed altogether, and should be discarded and replaced with a new one, which could be gotten by mail. As my stomach got heavy and my appetite vanished, I imagined starting over, throwing away the last three months of my digital existence. I felt so empty, a hollow man, and there was nobody around or to call who could fill me up again. I wasn't really angry, just slowly settling into a profound and total despair.
After some blank-faced pacing, I booted up my system in single-user mode, opening onto a black screen with a white Unix prompt, and started entering obscure commands I had seen in the forums (such as: "fsck -fy /disk0s2"), which confirmed the invalid node structure, but failed to fix the problem. Fiddling around in a daze, I moved the offending corrupted file — WeFeelFine.mbox (the Mailbox file containing the 19,000+ We Feel Fine emails exchanged since 2005) to a new location, and issued the command, "reboot". This time the system started up as normal, and I rushed to grab an external hard drive to start backing up my data.
As I understand it, my system is not fixed now — it is living with a cancer that has been temporarily suppressed, but which can come out of remission at any moment. The corrupted WeFeelFine.mbox file cannot be deleted — for some reason the operating system won't allow it — so I have to learn to live with it there, sick and contagious but quarantined, staring out at me from the sidebar every time I check my email, tempting me to drag something onto it, which would cause the cancer instantly to come roaring back again.
I have sent away for a $100 program called DiskWarrior, which apparently knows how to fix the invalid node structure and heal the broken Catalog B-Tree. I hope this computer chemotherapy will give my machine a new chance at life. God knows it deserves one.