Understanding File system in Linux/Unix
- Contains the executable programs that are part of the Linux operating system.
- Many Linux commands such as cat, cp, ls, more, and tar are located in /bin.
- Example ls, cat, cp.
- All the devices like input devices, sound card, modems are stored.
- It is a virtual directory that contains devices files.
- Example : /dev/udp, /dev/urandom, /dev/sda1
- Contains config folder of entire operating system.
- All the global setting like ssh, telnet, and smtp/pop3 mail servers.
- Also contains system’s password file like group lists, user skeletons, and cron jobs.
- Example: /etc/resolv.conf, /etc/logrotate.conf
- Default directory for users to store the personal files.
- Example /home/saugat, /home/sachit
- contains binary executables typtically used by system admnistrator only available to root.
- Mostly used for system maintenance purpose
- Commands such as mount, shutdown, umount, reside here
- Example: /sbin/halt/ /sbin/ip6tables
- contains shareable and read only data
- contains binaries, libraries, documentation and source code for second level program
/usr/bin : Contains executable files for many Linux commands. It is not part of the core Linux operating system.
/usr/include : Contains header files for C and C++ programming languages
/usr/lib : Contains libraries for C and C++ programming languages.
/usr/local : Contains local files. It has a similar directories as /usr contains.
/usr/sbin : Contains administrative commands.
/usr/share : Contains files that are shared, like, default configuration files, images, documentation, etc.
/usr/src : Contains the source code for the Linux kernel.
Includes user specific files such as mail message, database of installed programs, log files etc.
/var/cache: Storage area for cached data for applications.
/var/lib: Contains information related to the current state of applications. Programs modify this when they run.
/var/lock: Contains lock files which are checked by applications so that a resource can be used by one application only.
/var/log: Contains log files for different applications.
/var/mail: Contains users emails.
/var/opt: Contains variable data for packages stored in /opt directory.
/var/run: Contains data describing the system since it was booted.
/var/spool: Contains data that is waiting for some kind of processing.
/var/tmp: Contains temporary files preserved between system reboots
- All the temporary files are store here.
- The files under this directory are deleted when system is rebooted.
- For example: when new program is installed it use /tmp/ to put files during installation that won’t be needed after the program is installed.
- Default location for mouting devices like cdrooms, floppy disk dries, USB memory sticks etc.
- Example : /mnt/cdroom
- contains information about system process
- virtual file system that contains information about file system.
- Example /proc/cpuinfo, /proc/swaps
- share libraries are stored(perl, python, C, etc.)
- /lib/ are also a kernel modules
- Example: ld-2.11.1.so, libncurses.so.5.7
- Config file for add on Application software are found here.
- Third party application should be installed in this directory.
- Home directory of system administrator.’root’.
- Root user has write privilege under this directory
- Contains everything required for boot process.
- Stores data that is used before the kernel begins executing user-mode program.
- Example: /boot/boot.b, /boot/chain.b, /boot/config-kernel-version