In the early 1990s, a Finnish student at the University of Helsinki named Linus Torvalds became fed up with the operating system choices available. Linus wanted to use Unix, but unfortunately or fortunately, depending on how you see it, Unix was far too expensive for a student. Left with only one choice, Linus started to build his kernel “Just for fun”1 from scratch.
The kernel of this operating system was first release by Linus Torvalds in 1991. After that, with the addition of user space applications, it became the Linux operating system. Linux source code is freely available and it is community based development project. Multiple teams’ works in collaboration to enhance the capability of Linux operating system and it is continuously evolving.
Linux is well-known as a stable and reliable platform, providing database and trading services for companies like Amazon, the well-known online bookshop, US Post Office, the German army and many others. Especially Internet providers and Internet service providers have grown fond of Linux as firewall, proxy- and web server.
Modern Linux not only runs on workstations, mid- and high-end servers, but also on "gadgets" like PDA's, mobiles, a shipload of embedded applications and even on experimental wristwatches.
There are 5 types of users available in Linux.
(i) System user (Admin user who control the whole system nothing but root user).
(ii) Normal user (Created by the Super user. In RHEL - 7 the user id's from 1000 - 60000).(iii) System user (Created when application or software installed ).(In RHEL - 7 the System users are Static system user id's from 1 - 200 and(
(iii) Dynamic system user user id’s from 201 - 999).
(iv) Network user (Nothing but remote user, ie., who are login to the system trough network created in Windows Active Directory or in Linux LDAP or NIS).
(v) Sudo user (The normal users who are having admin or Super user privileges)
LINUX system
