Can one now help?

Marko Vojinovic vvmarko at gmail.com
Mon Jul 19 03:35:36 UTC 2010


On Sunday, July 18, 2010 23:35:34 Parshwa Murdia wrote:
> > the result of "fdisk -l /dev/sda" is as follows:
> > 
> > Disk /dev/sda: 250.0 GB, 250059350016 bytes
> > 255 heads, 63 sectors/track, 30401 cylinders
> > Units = cylinders of 16065 * 512 = 8225280 bytes
> > Disk identifier: 0xfedcfedc
> > 
> >    Device Boot      Start         End      Blocks   Id  System
> > 
> > /dev/sda1               1        5737    46082421    7  HPFS/NTFS
> > /dev/sda2            5738       30400   198105547+   f  W95 Ext'd (LBA)
> > /dev/sda5            5738        9561    30716248+   7  HPFS/NTFS
> > /dev/sda6            9562       13385    30716248+   7  HPFS/NTFS
> > /dev/sda7           13386       15935    20482843+   7  HPFS/NTFS
> > /dev/sda8   *       15936       15961      204799+  83  Linux
> > /dev/sda9           15961       28596   101487615+  8e  Linux LVM
> > 
> > I don't know why there is no entry for sda3 and sda4. I guess the linux
> > root partition to be sda8? or it should be sda9?

Ok, as an aftermath, for educational purposes :-) :

* The partition /dev/sda1 is what corresponds to the C: partition on Windows. 
It is the so-called "primary" partition, and only 4 of those can exist on the 
disk. They are named /dev/sda1 through /dev/sda4 in Linux.
* You don't have any more primary partitions, and /dev/sda2 is instead a so-
called "extended" partition, which is actually only a "container label" for 
all other partitions that follow, which are not primary.
* The first partition contained inside the extended one is /dev/sda5 (if the 
number were less than 5 it would correspond to a primary partition, and could 
not be inside the extended one). This one is probably the Windows D: 
partition.
* As above, /dev/sda6 and /dev/sda7 are also members of the extended 
partition, and correspond to your Windows drives E: and F:. Now, somewhere in 
between those letters Windows might stick the CD/DVD drives and assign its 
letters differently. The CD/DVD drives are *not* listed by the above fdisk 
command, and I can only guess how Windows will order its drive letters.
* The /dev/sda8 partition is also a member of the extended one, and most 
probably the Fedora /boot partition, where the kernel and grub files reside. 
Windows does not show a letter for that one, since it doesn't recognize Linux 
partitions in general.
* Finally, the /dev/sda9 partition is again not a real partition, but again a 
container like /dev/sda2 (although of quite different type). It is contained 
inside /dev/sda2, and it contains yet more partitions. This container is of 
LVM type, and contains all other Linux partitions (probably root and swap) 
inside. These partitions are not listed by fstab.

I know it sounds complicated. And believe me, it is. That is what you get when 
you mix very old standards (only four partitions allowed on the disk) with 
patched technologies and new hyped ideas --- you get one primary partition, 
and several of them inside LVM which is inside the extended partition which is 
a bogus primary one.

Don't ask me how did disk partitioning evolve into such a stupid state. When 
IDE disks were being standardized (long time ago), nobody dreamed that one day 
you might wish to have more than 4 partitions on the disk, dual boot system 
and wish to be able to resize partitions on a live disk. So they invented a 
stupid and shortsighted standard which had to be patched after it became 
*obviously* shortsighted...

> > mounting this (for both sda8 and sda9), it shows me the error:
> > *
> > mount: unknown filesystem type 'lvm2pv'* (in the terminal)
> > 
> > and once:
> > *
> > mount: you must specify the filesystem type* (in the terminal)
> > 
> > so again it is not getting either mounted.

Of course, as you already found out yourself, mounting partitions inside the 
LVM container is not the same as trying to mount the LVM container itself (the 
latter is bound to fail, since it is just a container, not an actual 
partition...). Hence the errors.

Although I am confused about sda8, it is type 83 (ext2/3/4), that one *should* 
have worked. But nevermind now... ;-)

And of course, I missed to remember that you probably have a LVM container by 
default, so my original instructions didn't work as I thought they should. My 
bad. But you found out what is the proper procedure for that case via google. 
:-)

> [root at localhost oldfedora]# cat /etc/fstab
[snip]
> I don't understand why it is wrong?

Well, the fstab file is a file that contains rows and columns. Specifically, each 
row must contain 6 columns. Column entries are separated with a space. So for 
example, the line

tmpfs /tmp tmpfs defaults 0 0

has "tmpfs" in the first column, "/tmp" in the second, "tmpfs" in the third, 
"defaults" in the fourth, and "0" in fifth and sixth. And that is ok.

Now, if you look at one of the lines you modified initially, for example:

/dev/mapper/VolGroup-lv_root /  ext4    defaults, noatime, nodiratime  1 1

I am counting 7 spaces total, which means that line has 8 columns, which the 
computer does not tolerate. The "defaults,", "noatime," and "nodiratime" are 
distributed into three columns, when they should all be in only one (4-th 
column). When you introduced extra spaces, you introduced extra columns, which 
is wrong. The right line should be

/dev/mapper/VolGroup-lv_root /  ext4    defaults,noatime,nodiratime  1 1

Now there are no extra columns, you have 5 spaces delimiting 6 columns total, 
and the data in the 4-th column is "defaults,noatime,nodiratime", as it should 
be. The computer knows how to interpret and understand this.

If you want to read more about the structure and syntax of the fstab file, type 
"man fstab" in the terminal, and read on.

The "man" command stands for "manual", and gives you usage instructions for 
whatever command you wish to know about. Try "man mount", "man ls", "man cd", 
"man vgscan", and so on. Try even "man man", there is a manual about using the 
manual. :-)

If you want to be able to use Linux with greater power, you need to be 
skillful in using the terminal. Reading manual pages is the first place to 
start learning. If you are very determined to learn, read "man bash".

If you are a masochist, read "man bash" twice. ;-)

> But after much pondering over, I just deleted the gap between the
> nodiratime,noatime and defaults, and really speaking after that only i was
> able to boot from the original fedora.

Precisely. After the explanation above, it should be clear what was wrong and 
why it is now correct.

Best, :-)
Marko




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