How to fix the MiniMagick error: 'unable to extend cache' on MacOSX?

Question

When I'm trying to upload a picture I receive an error message: This is the error message I get:

Thumbnail Failed to manipulate with MiniMagick, maybe it is not an image? 
Original Error: 
  Command ("mogrify -resize x101163 -gravity Center -background rgba(255,255,255,0.0) -extent 118x100000 /var/folders/jk/hwpphsbx71ncw5rz6mjs21yc0000gn/T/mini_magick20131210-54787-106bvlz.png") 
failed: {
  :status_code=>1, 
  :output=>
    "mogrify: unable to extend cache `/var/folders/jk/hwpphsbx71ncw5rz6mjs21yc0000gn/T/mini_magick20131210-54787-106bvlz.png': 
    No space left on device @ error/cache.c/OpenPixelCache/3638.\n"
}

It seems that a certain cache somewhere is full. I also get a message from my terminal that it's full. Is there a way to clear it - without destroying anything?

Things I've checked:

• My hard disk has enough storage left

Answer 1

It seems Imagemagick (v6.7.7-10) have a bug, or at least is not efficient enough, and while doing some stuff (in my case convert *.jpg myfile.pdf) use a lot of disk space, almost 100MB per second in my case. You could see this opening another terminal and running watch df -h. AFAIK there isn't a solution other than running the command with a root partition big enough to complete the task.