Directory Tree of Ubuntu

Directory     Content
bin     Essential command binaries
boot     Static files of the boot loader
dev     Device files
etc     Host-specific system configuration
home     User home directories
lib     Essential shared libraries and kernel modules
media     Contains mount points for replaceable media
mnt     Mount point for mounting a file system temporarily
proc     Virtual directory for system information (2.4 and 2.6 kernels)
root     Home directory for the root user
sbin     Essential system binaries
sys     Virtual directory for system information (2.6 kernels)
tmp     Temporary files
usr     Secondary hierarchy
var     Variable data
srv     Data for services provided by the system
opt     Add-on application software packages