Download Unix – Linux

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
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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