The /bin directory contains executable files, commands used in single-user mode and commands required by system users such as
- ps – list of processes
- ls – list of the contents of a directory
- cp – copy files
Commands that are not essential for the system are placed in the /usr/bin directory
Essential binaries related to system are placed to /sbin, such as ifconfig and shutdown.
The /dev directory contains device nodes, pseudo-files, used by most hardware and software devices. It is empty on the disk when not mounted. All the entries are created by the udev system. Some nodes are
- /dev/sda1 – first hard disk
- /dev/dvd1 – first dvd
The /var directory contains files that their size changes like log files (/var/log) , print queues (/var/spool) and temporary files (/var/tmp).
The /etc directory contains system configuration files. There no binary files but there are some executable scripts. passwd, shadow and group are example files in /etc directory.