Root "/" file system:
The kernel needs a root file system to mount at start up. The root file system is generally small and should not be changed often as it may interrupt in booting.
The root directory usually does not have the critical files. Instead sub directories are created. E.g. /bin (commands needed during bootup), /etc (config files) , /lib(shared libraries).
/usr filesystem :
this file system is generally large as it contains the executable files to be shared amongst different machines. Files are usually the ones installed while installing Linux. This makes it possible to update the system from a new version of the distribution, or even a completely new distribution, without having to install all programs again.
Sub directories include /bin, /include, /lib, /local (for local executables)
/var filesystem :
this file system is specific to local systems. It is called as var because the data keeps changing.
The sub directories include /cache/man (A cache for man pages), /games (any variable data belong to games), /lib (files that change), /log (log from different programs), /tmp (for temporary files)
/home filesystem: -
this file system differs from host to host. User specific configuration files for applications are stored in the user's home directory in a file.
UNIX creates directories for all users directory. E.g /home/my_name. Once the user is logged in ; he is placed in his home directory.
/proc filesystem :
this file system does not exist on the hard disk. It is created by the kernel in its memory to provide information about the system. This information is usually about the processes. Contains a hierarchy of special files which represent the current state of the kernel.
Few of the Directories include /1 (directory with information about process num 1, where 1 is the identification number), /cpuinfo (information about cpu), /devices (information about devices installed), /filesystem (file systems configured), /net (information about network protocols), /mem (memory usage)
