fdisk problem

sachin1361 · 03-10-2007, 01:40 AM

Can you please tell me how much cylinder size is equal to 1 MB. Below is the /dev/sda5 size.. What is the size of this parttion (in MB or GB) what this block signifies and ID means ?????

Device Boot Start End Blocks Id System

/dev/sda5 8756 8856 610407 82 Linux

and sometimes + is marked after block ..what is this ??
/dev/sda1 1 4854 38989723+

stress_junkie · 03-10-2007, 08:50 AM

I get 298 MB for the partition size.

Blocks on disk are 512 bytes.
Two blocks = 1 KB. (1024 bytes)
1 MB = 1024 bytes times 1024 bytes = 1,048,576 bytes.

610,407 blocks times 512 bytes = 312,528,384 bytes.

312,528,384 bytes divided by 1 MB = 298.05029296875 MB.

Note that hard drive manufacturers will often calculate 1 MB = 1000 x 1000 and they will calculate 1 GB as 1000 x 1000 x 1000. This obviously makes it look like they have more capacity than they actually do have since they are dividing the total number of bytes on the disk by a smaller number than if they used 1024 x 1024 for 1 MB and 1024 x 1024 x 1024 for 1 GB.

If we used those misleading values then your partition would falsely appear to be 312.5 MB. It's about exactly what the words mean. A megabyte is a power of two rounded down to the nearest million while a million bytes is an exact measurement. This is why it is possible to purchase a 200 GB hard drive and your computer will say that it is only 186 GB.

200,000,000,000 divided by (1024 x 1024 x 1024) equals 186.2645149230957031

Jaqui · 03-10-2007, 08:57 AM

SHHH!!!

don't tell people that hardware manufacturers take after Politicians and Microsoft and lie to everyone.
people have to have something they can trust. ~eg~

bathory · 03-10-2007, 09:11 AM

You should take a look at README.fdisk found in utils-linux package for a full expalanation. Anyway, blocks is the size of the partition in kbytes and id is the hex value of the type of the partition. Hence in your case sda5 is 610,4M swap (id=82) partition.
The + flag means that the partition has an odd number of sectors which will be wasted.

stress_junkie · 03-10-2007, 12:04 PM

Quote:

Originally Posted by bathory

You should take a look at README.fdisk found in utils-linux package for a full explanation. Anyway, blocks is the size of the partition in kbytes and id is the hex value of the type of the partition.

I couldn't find the README.fdisk on my computer.

A quick experiment proved you to be correct. The fdisk utility does report blocks as 1K units or something like that.

Code:

root> fdisk -l /dev/hda
...
/dev/hda3   *        1156        2249     8787555   83  Linux
...

root> df -h /dev/hda3
Filesystem            Size  Used Avail Use% Mounted on
/dev/hda3             8.3G  2.2G  5.8G  28% /mnt/hda3

Well. I think I'll just go home now.

bathory · 03-10-2007, 04:18 PM

Quote:

Originally Posted by stress_junkie

I couldn't find the README.fdisk on my computer.

In slackware the README.fdisk is located in /usr/doc/util-linux-2.12r/README.fdisk. You can read it online here

Regards