I've been using linux systems since 1994 and I've never defragged one.
Unix filesystems are naturally more resistant to fragmentation than pc
filesystems, and in any case, it's not an issue.

I've heard of various defrag projects over the years, which as far as I
can tell never found a niche, but recently I heard that there may be a
defrag utility for the ext4 filesystem, for those who really pine for
the old days of defragging their disks.