Joel Granados wrote:
On Thu, May 21, 2009 at 09:36:41AM -0600, Curtis Gedak wrote:
Joel Granados wrote:
Hello list.
The question is: why does parted call renumber partition funcion every
time it removes/deletes a partition?
Hi Joel,
Perhaps it has something to do with MSDOS partition tables and logical
partitions?
When a logical partition is deleted, it affects the partition numbers of
each logical partition that follow in the chain.
For example, an extended partition contains four logical partitions A,
B, C, and D. These logical partitions are accessed by the operating
system as follows:
* Partition A as /dev/sda5.
* Partition B as /dev/sda6.
* Partition C as /dev/sda7.
* Partition D as /dev/sda8.
If partition B is deleted, then the remaining logical partitions will be
accessed by the operating system as follows:
Yes, but this is due to parted renumbering. That is, if parted did not
renumber the partitions, the OS would access the partitions as sda5 sda7
sda8.
I agree that the OS might continue to access the partitions as sda5 sda7
sda8. However this would only last until the next reboot of the system
when the partitions would be assigned sequential numbers with no gaps.
The following article provides a good explanation of how the chains work
with Extended Boot Records and logical partitions:
http://en.wikipedia.org/wiki/Extended_boot_record
I believe that this physical chaining of one logical partition to the
next dictates the partition number assigned to each logical partition.
Please note that using fdisk to delete a logical partition produces the
same renumbering result - the logical partitions after the deleted
logical partition are renumbered.
I suspect this behaviour has to do with the nature of chaining one
logical partition to another within an extended partition.
If parted were to ignore the partition renumbering, then all might be
fine while the system is up and running. However, on a reboot the OS
would assign sequential numbers to the logical partitions and there
would be no gap in the numbers.
If a user were to make system changes, such as updating /etc/fstab,
based on partition numbers that were not renumbered by parted, then
these changes could be incorrect upon a subsequent system reboot.
Does that make sense? :-)
I apologize in advance if we are talking about two different things. A
while back I had started investigating the parted code. However, when
the requirements to compile the code changed to require updated tools
not packaged by my distribution, I ceased the endeavour.
* Partition A as /dev/sda5.
* Partition C as /dev/sda6. Note the change in device name.
* Partition D as /dev/sda7. Note the change in device name.
This is just a guess since I haven't looked into the renumber partition
function. :-)
Regards,
Curtis Gedak
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