Default Ubuntu directories and their purposes

/ 

The root of the virtual directory. Normally, no files are placed here

 
/bin 

The binary directory, where many GNU user-level utilities are stored 

/boot 

The boot directory, where boot files are stored
 

/dev 

The device directory, where Linux creates device nodes
 

/etc 

The system configuration files directory
 

/home 

The home directory, where Linux creates user directories
 

/initrd 

Location of files used during the boot process if a RAM disk is required
 

/lib 

The library directory, where system and application library files are stored
 

/lost+found 

Directory where lost filesystem nodes are stored. If your disk crashes, look here for missing files
 

/media 

Mount point used to mount external disks in the virtual directory
 

/mnt 

The mount directory, a common place for mount points used for removable media
 

/opt 

The optional directory, often used to store optional software packages
 

/proc 

Controlled by the kernel, this special directory provides information about
internal kernel processes and can be used to send information to the kernel
 

/root 

The root home directory
 

/sbin 

The system binary directory, where the GNU admin-level utilities are stored
 

/srv 

Used as a base directory on the Ubuntu server platform for data that is served to others, such as web pages
 

/sys 

Similar to the /proc directory, used by the newer Linux kernel to communicate with plug-in kernel modules
 

/tmp 

The temporary directory, where temporary work files can be created and
destroyed
 

/usr 

The user-installed software directory
 

/var 

The variable directory, for files that require write privileges, such as log files