Unix – Linux CS3353 Ssystem Administration

OS The Operating System – Acts as the interface to all software, hardware, and users of a computer. – Requires a file system for organizing files – Must maintain its viability to prevent other programs, hardware, users, etc, from impeding its operation. Unix and its variants will accomplish the above.

UNIX Consists of core software known as the kernel – The kernel acts to share resources of the system with all running processes. – A process is a collection of resources associated with a running program.

UNIX By 1973, it was a complete Written using the C program language. – Multi user – Multi task – Multi processor

UNIX Variants There are many variants of UNIX. – BSD (1977) – AT&T System V (1983) – Linux (1991, Linus Torlvalds, Helsinki Finland) – Mac OS X is a UNIX based variant (1999).

UNIX Multi-user – The user accesses the computer in an environment that is separated from other users sharing the computer’s resources. – Access is through a verification process known as logging-in: Enter a user-id and password. – The OS creates an environment known as the “shell” for the user after the login is complete.

The Unix/Linux Shell A command line interpreter The shell is tagged with the user’s ID. The user can have multiple independent shells running simultaneously.

Shell Types sh = Bourne shell csh = C-shell ksh = korn shell, an enhanced c-shell. bash = enhanced Bourne shell. The new standard for shell scripting.

The UNIX-Linux OS The Unix/Linux OS consists of: – The kernel – the main controlling program that is started at boot time. – Processes that support the kernel and all other activity – The File system – Utilities