Hi,

I have been looking out http://www.tldp.org/LDP/Linux-Filesy...ierarchy/html/
I read it,but unfortunately couldn't crack it's technical jargons used.
I want to ask ,
1.What do we mean by a file system, is it like Fat32 and NTFS in Windows. I know its a way of organising files.So /dev,/etc,/home all are file systems(terms are used in manual)..if they are then what is ext3?
I am confused,please somebody explain very simple and practical aspects.
2.Also what is mount? Why do we mount?

May be going through so many manuals ,have confused my mind.
I want to understand these things very simple,coz that is what my level of understanding is right now being a newbie.

Thanks in Advance..and may be I would understand more if you can explain things with reference to Windows.

Cheers!!

1. Yes, Fat32 and NTFS are filesystems for windows, Linux uses filesystems such as ext3, jfs, reiserfs, xfs and many many others.

2. Because that's how you actually access a filesystem. mounting is the act of opening a filesystem and making it available to the user. Windows obviously has to do this as well, it just hides it more, but your NTFS drive is mounted as "C:" or whatever.

I'll try....

A filesystem is a structure on a storage device that provides an interface between the user and the actual mechanics of how the data is stored. When you access a file or directory, your request is mapped to physical locations using "inodes". A particular file may have many inodes pointing to different chunks of data (which are stored wherever the system could find the right amount of available space.

http://en.wikipedia.org/wiki/Filesystem

Types of filesystems include FAT, NTFS, EXT, Reiser, and many more.

/dev, /etc, /home, etc. are not filesystems---they are typical directories used in the Unix filesystem. Now we see a slightly different use of the term "filesystem"--meaning the organization of the directories.

"Mount" comes from the old days of tape drives. When your program asked for some specific data, an operator had to go find the right reel of tape and mount it on a drive. In modern systems, it is useful to think of mounting as "connecting" a filesystem to the "root" filesystem on which the operating system is running.

I understand the concept of filesystem in Mainframe and Windows(Fat tables and root directory) what is there equivalent in linux??
and where are these tables or structures located to manage files(using inodes) and directories.
Is there any link which explains this in depth and diagramatically??
TIA.

Cheers!!

Hi,

Why re-invent the wheel> 'Understanding UNIX/Linux file system'.
This link is 'Part I' of a 5 part definition.

The above link and others available from 'Slackware-Links'. More than just Slackware® links!

AND---you can look up the official spec. for any particular system--eg EXT. NTFS is proprietary, so that will be harder.

file systems:

windows:
FAT
FAT16
FAT32
NTFS ... etc...

unix/linux:

ext2
ext3
reiserfs
jfs
xfs ... etc...

your HDD stores the data in "inodes" but when you are in a gui interface you dont see 0's and 1's, what you see are names and icons... but those icons are actually pointing to specific parts of your HDD through the inodes... so:

windows:
A:/
C:/
D:/
E:/

unix/linux:

/
/home
/etc
/root

you get the idea right?

now Windows "mounts" c:/ to inode "35654" automatically when booting... you have never seen the process and will never understand it because windows is made for "dumb" people that should not understand anything... just point and click and the world is pink...

in unix/linux the basic root is mounted in / automatically and some other important basics, but you can also mount (or point to if you understand it better that way) additional files, folders or drives...

in windows you will never be able to mount a file to a folder, for example an iso file, unless you download sofware that does that for you like daemon-tools and other which are usually commercial... in linux you just simply:

mkdir /home/temp (this can be any dir anywhere. You just have to point to it when you mount)
mount /home/myiso.iso /home/temp...

and then you can simply cd to that dir and see the iso file as a folder... or even by point and click your way to the folder...

I hope you understood what i tried to say... post #2 was a clear explanation to your question but it seems that it was not enough, this post is actually expanding #2's info.

Thanks to all.
@RaptorX : nice and simple explanation.

cheers!!

Hi,

Look it's not that difficult.

In UNIX everything is treated as a file. You have a filesystem that is created on a storage device for storing and organizing computer files/data they contain to make it easy to find and access the same.

The filesystem can be formed in different formats, i.e. ext2/3/4, jfs, reiserFS among other types. The ext2/3/4 format is a typical format. I prefer the ext3 as it is a journaled filesystem to store my files/data.

When you mount the '/' you are mounting a file that is on a 'dev' file that contains files/data to operate the OS. You treat things as files when working or using UNIX. These files are stored across the media and are pointed to by 'inodes' which stores basic information about a regular file, directory, or other file system object(s).

As for the definition of 'FAT' it does predate M$. Most people associate FAT with M$ because certain patents for the format. The original FAT was developed for DR CP/M which some say that MS-DOS is based on. But that's another story. FAT has been a useful filesystem for many. FAT has migrated to FAT/12/16/32 as a usable filesystem on many platforms for M$.

'NTFS' is another filesystem, this is far superior to the FAT based system except for the overhead required to store the files/data on all storage media.

'NTFS-3g' is variant that allows UNIX-like systems to fully support a 'NTFS'.

Hopefully you read some of the links to enlighten your understanding about 'filesystems'.

As you say, a filesystem is a way to organize the date so it's easily accessible by the average user. There are many with very different features that can work in one or another OS, or a number of them.

Filesystems (fs for short) are stored in whatever device fits the occasion, and they are attached to your main fs by "mounting" them. In that sense, you can attach an fs into whatever directory you want.

When you speak about the /usr fs, you are really talking about the fs that has been attached (by mounting it) to /usr. Strictly speaking, /usr is just a directory, like any other, but when it has a proper fs mounted on it, it's correct to speak about the /usr fs. It might be formatted with ext3 or whatever, that's irrelevant. It's like when you speak about the john doe's car you know that john doe has a car, it doesn't really mean that the car is named "john doe". It can be a lamborghini, a porsche or a renault.

Mount attaches a new fs into your root one so it's accesible by you. Windows and other OSes do the same thing, it doesn't really matter if you call it My Documents, D: or /home/i92guboj. Windows likes to hide all these things, which for some is a good thing, for some is a bad thing. Note that, being the mechanism hidden, you have absolutely no way to fix the things when a volume becomes corrupted in any strange way. For example, sometimes the cdrom tray will not open because you can't unmount it. In linux you can always force it unless there's some really nasty problem at kernel level.



I haven't ever heard the concept of "root directory" in windows, and FATs do exist only in the FAT series of filesystems. Other filesystems will use different structures, for example, i-nodes or some kind of balanced tree.

Not all fs's use i-nodes either.

About the technical insides, they are *broadly* different for each fs. There's no standard location to store information about the files, and there's no standard structure that is common to all the types of fs.