Absolute and relative paths and The kernel

Absolute and relative paths:

A path, which is the way you need to follow in the tree structure to reach a given file, can be described as starting from the trunk of the tree (the / or root directory).

In that case, the path starts with a slash and is called an absolute path, since there can be no mistake: only one file on the system can comply.

In the other case, the path doesn't start with a slash and confusion is possible between ~/bin/wc (in the user's home directory) and bin/wc in /usr, from the previous example. Paths that don't start with a slash are always relative.

In relative paths we also use the . and .. indications for the current and the parent directory. A couple of practical examples:

When you want to compile source code, the installation documentation often instructs you to run the

command ./configure, which runs the configure program located in the current directory (that came

with the new code), as opposed to running another configure program elsewhere on the system.

In HTML files, relative paths are often used to make a set of pages easily movable to another place:

<img alt="Garden with trees" src="../images/garden.jpg">

Notice the difference one more time:

manish:~> ls /mp3

ls: /mp3: No such file or directory

manish:~>ls mp3/

oriental/ pop/ sixties/

The kernel:

The kernel is the heart of the system. It manages the communication between the underlying hardware and the peripherals. 

The kernel also makes sure that processes and daemons (server processes) are started and stopped

at the exact right times. 

The kernel has a lot of other important tasks, so many that there is a special kernel-development mailing list on this subject only, where huge amounts of information are shared. 

It would lead us too far to discuss the kernel in detail. For now it suffices to know that the kernel is the most important.