Rsync

rsync copies files and directories. It is often used for backups, or duplicating directory contents on a remote server. rsync can copy only changed files, and can use SSH to securely copy the file.

Common Options

-a - Combo flag, same as -rlptgoD (recursive; copies symlinks; preserve: permissions, modification times, group, and owner; device/special)

dir vs dir/:
dir - Copy the directory
dir/ - Copy the contents of the directory

Sync Directories on the same computer

rsync -a dir1/ dir2 - Copies the contents of dir1 into dir2

References

1. rsync man page
2. d