i want to know what the following means in fdisk expert command


Expert command (m for help): m
Command action
b move beginning of data in a partition
c change number of cylinders
d print the raw data in the partition table
e list extended partitions
f fix partition order
g create an IRIX (SGI) partition table
h change number of heads
m print this menu
p print the partition table
q quit without saving changes
r return to main menu
s change number of sectors/track
v verify the partition table
w write table to disk and exit



here "c" is to change the cylinders what does it mean.
Number of cylinders (1-1048576, default 4865):

i changed the number of cylinder from 4865 which was default to 5000 and then by "w" i complete the process but after restart the cylinder was default i.e 4865.\

My question is why :-
the cylinder number is (1- 1048576 , default 4865) what does it mean.
why the cylinder no is between 1-1048576.
for rest i'm working on it....

Why jump in the 'expert' section? fdisk is challenging and potentially damaging without that!
'm' is repeated as help and sort of print so far, confusing, yes but you have to work though the weird logic till it makes sense. I suggest you look on the net for linguistic work thoughs that make more sense than man pages.
Fred.

The OpenBSD install instructions have a good (though very technical) tutor about disks and stuff like cylinders - give it a read! See http://openbsd.org/faq/faq4.html

It's not the "cylinder number"---it is the number of cylinders.

There was once an archaic way of addressing drives---called "CHS" (for "Cylinder, Head, Sector") At one time I think there was physical basis, but now it's just units fed into the SW.

Look at the units in "fdisk -l". Can you imagine that certain values for the number of cylinders might not be allowed?

What problem are you trying to solve? Why do you need to change this parameter?


Note: changing things like this on a formatted disk with data might have unhappy results.......

yeah i did the format of disk due to the expert option but i just want to learn it.
and sorry for that its the "number of cylinders".
In my previous thread of "fdisk -l" you told that the number of cylinder is "4865" its default .....it means the number of cylinders present in disk is "4865" ..... so what's the basic need of this command ........

till i know about that i changed the number of cylinder from "4865" to "5000" then it changed and after restart the cylinder changed to "4865"..
so i want to know what is the basic need of this command ......hope you understand what i want to ask...

and one most important question in which file the entry of hard disk is done .....

Sorry, but I still don't understand why you are concerned with changing the number of cylinders---just simple curiousity?. I do not know the answer, and the way I would approach is to simply try some experiments. I don't have a computer at the moment where I would risk this.


I don't understand.

I suggest you read & digest these

http://en.wikipedia.org/wiki/Cylinder-head-sector
http://en.wikipedia.org/wiki/Master_boot_record

and follow a few of the links.

in which file entry of hard disk is done means if we want to create a new partition then how the system shows that entry where that entry is done in system . In "/etc/fstab" the entries of file system type is done . So like "fstab" where the entry of fdisk's all entries are done.

Not in a file---in the MBR.

See the link supplied by chrism01

sorry for the new thread but no one was able to understand what i'm asking so i started new thread .
and as mentioned in the diffrent thread i write the changes after changing the number of cylinders and it changed but after restart the cylinder came to default .
so i just want to know how to change no. of cylinders in expert option of "fdisk" command . and if it does not change then what is the use of these options ..
please don't send the link of "mbr or cylinder head sector" .
i know that and i studied all the options of fdisk only problem is with the expert options .
hope u understand what i want to ask ..
and one more question :-
if we run the command "fdisk -l"
then on some blocks the "+" is present ...
how can we create the "+" on all the partitions and if we want to remove the "+" then how can we remove it ..
plz don't explain why the "+" is used...

Yes, Sir!
Sir. Another possibility is that some were able to understand but you, Sir, did not understand their responses.

One possibility, Sir, is that the cylinder changing feature of fdisk was once useful and effective but that it is not useful for modern HDDs (for reasons mentioned already). Perhaps fdisk writes cylinder changes to the HDD and the HDD silently (no error message) ignores them -- because they are meaningless and harmless so there's no benefit in making a fuss.

No Sir, I have not even thought of posting it.

Do you know what the "+" means, Sir? I don't and it is not in the man page.

No, Sir. Actually I couldn't because I don't know why it is used -- but I didn't even think of explaining it. No, Sir, I would not do that. Sir.

you should dig up all the man pages, materials and references given and try to understand in detail about the following
1. Hard disk - old and new type
2. fdisk
3. MBR


good you are trying to understand and experiment, but your language is complicated...　

Kaushal*;

I can appreciate your frustration in trying to understand the details of something like disk partitioning. But please be aware that there is a language barrier here, and this will make communications difficult. You might want to consider getting someone to help you with the english.

Another bit of advice: Don't try to tell people not to explain things to you. Most members here will do their very best to address your questions--based on their interpretation of what you are trying to do. If they tell you something that you already know, you are free to ignore it.

For the question on the plus sign (+), Google found this:
http://www.google.com/search?hl=en&c...&aq=f&oq=&aqi=
Searched using ("fdisk plus sign")

thanks for your response.
plz. suggest why the options like "change cylinder no. , change sectors etc. " are given in expert command .
how it is used ?
i tried a lot to find .
once again thanks for the response .

If you read the various documents that have been suggested, you will see that some of the nomenclature and conventions are simply tradition. The fact is that there is no real reason in modern systems to be changing or using cylinder, head, and sector settings.

To answer your specific question "How is it used?":
For most of us, it's not.......