What is mtree?

mtree(8) is a utility included in the base system (/usr/sbin/mtree) and can be used to compare two directory structures thus allowing you to spot any kind of difference. By default it does this by comparing file size (in bytes) and type, last modification time, file owner, group owner, the permissions as a numeric value, any optional flags (see ls -lo, and also chflags(1)) and finally any optional soft or hard links the file might have.

But there's a whole lot more you can do here.

Why I'm writing this guide (short editorial section)

The main reason I'm writing this guide is because I think not many people use mtree to its full potential. But to make matters worse I also think the manual page doesn't do a good job. I mean... If all you do in the EXAMPLES section is to point people to some parameters without actually showing them any examples on how to use those...