REDHAT certifications

Journaling

Journaling avoids the time-consuming check that is automatically performed on a filesystem when it is abruptly unmounted for instance, as a consequence of a system crash.

System Calls

             Operating systems offer processes running in User Mode a set of interfaces to interact with hardware devices such as the CPU, disks,and printers. Putting an extra layer between the application and the hardware has several advantages. First, it makes programming easier by freeing users from studying low-level programming characteristics of hardware devices. Second, it greatly increases system security, because the kernel can check the accuracy of the request at the interface level before attempting to satisfy it. Last but not least, these interfaces make programs more portable, because they can be compiled and executed correctly on every kernel that offers the same set of interfaces. Unix systems implement most interfaces between User Mode processes and hardware devices by means of system calls issued to the kernel.

Network Commands

• ssh – SSH client (remote login program)                                    :

“ssh is a program for logging into a remote machine and for        
   executing commands on a remote machine”
Usage: ssh [options] [user]@hostname 
eg. ssh ­X guest@10.105.11.20        

                         
• scp – secure copy (remote file copy program) :
                          
“scp copies files between hosts on a network”
Usage: scp [options] [[user]@host1:file1] [[user]@host2:file2]
eg. scp file1.txt guest@10.105.11.20:~/Desktop/

What does Linux mean?

Linux is a free and open source Unix-like computer operating system originally developed for Intel x86-based personal computers by Linus Torvalds. The name Linux is used in many ways ie as a kernel, as an operating system as GNU/Linux (because so many of the Linux programs and commands come from the GNU project), the term Linux is also used for a Linux distribution. During the development Linux Torvalds stored the files to the FTP server (ftp.funet.fi) of Finnish University and Research Network (FUNET) under the name “Freax” ( a portmanteau of “freak”, “free”, and “x” for UniX). One of the administrators for the FTP server at the time, did not think that “Freax” was a good name. So, he renamed the project name to “Linux” (as a a portmanteau of Linus Torvalds and Unix) on the server.