File System Check. It's what the Unix world uses to put the file system right in the even of a crash. Windows has the same thing, they just don't call it fsck. But power off any Windows machine without shutting down properly and you'll see it run.
Modern Unixes usually have journalled file systems, which let fsck run very, very quickly, so quickly that you might not even see it at all, most of the time anyway.
Back when disks started to get bigger but RAM was still expensive, you'd sometimes run into problems where fsck couldn't get enough memory to store the information it needed to keep about the disk it was working on. The solution was to give fsck a "scratch file" on another filesystem or unused disk space for it to write temporary data to. That need went away as RAM became cheap, but it may come back again as extremely large hard drives grow beyond the memory capabilities of the OS itself. Then it will go away again as 64 bit OSes become common.
Unix people sometimes use this word as a replacement for that other four letter word that can't be used in so many venues. Like grep, it's probably not something you should do while new to the game.
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More Articles by Tony Lawrence © 2011-07-06 Tony Lawrence