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I'm experimenting with repartitioning in a KVM virtual. I have created a new qcow2 disk and mounted in a virtual. I'm experimenting with resizing the filesystem and repartitioning. I had previously unmounted and shrunk the filesystem using e2fsk -f and then resize2fs -M down to around 30k blocks. From what I've read online, to shrink the partition I now need to delete it, and then recreate it with a smaller block count (no less than the size of my file system) at the same starting sector. When I use fdisk to delete partition 1, and then recreate it, my lowest starting sector is 2048. As you can see in the output below, partition 1 originally starts at sector 8. What am I doing incorrectly?

pphan@www-dev1:~$ mount -l -t ext3
/dev/vdb1 on /wsrv type ext3 (rw)
pphan@www-dev1:~$ sudo umount /wsrv
pphan@www-dev1:~$ sudo fdisk -u -c -l /dev/vdb

Disk /dev/vdb: 1073 MB, 1073741824 bytes
9 heads, 8 sectors/track, 29127 cylinders, total 2097152 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0xad16440c

   Device Boot      Start         End      Blocks   Id  System
/dev/vdb1               8     2097143     1048568   83  Linux

Ubuntu 10.04.2 host and guest. I have tagged libvirt-KVM because I am not sure if this problem is specific to disk images.


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Next time, just make each partition into its own virtual disk. virtual disks are basically free, and can be resized at will without messing about with partitioning. – Dan Pritts Mar 18 '13 at 19:37
That's what I've got going on. At some point I may want to grow/shrink the image. – Pete Jun 6 '13 at 20:39
up vote 1 down vote accepted

This happens with physical disks as well. To be able to specify a lower initial sector, launch fdisk with the -cu options. You can also go to expert menu ('x') and use "move beginning of data in a partition" ('b') command.

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After i delete the partition (d) I then recreate a new primary partition 1 (n,p,1). I'm given the option of entering a first sector, but limited to 2048 as a minimum. Entering the expert menu (x) and then trying to 'move beginning of data in a partition' (b) will only let me move a minimum of 2048. I'm assuming its not possible move the beginning of data in a partition to outside the partitions sector range. – Pete May 3 '12 at 1:23
You may want to check also SU:… – S19N May 3 '12 at 15:27
Just tried doing this in a new 12.04 virtual and it worked – Pete Aug 8 '14 at 23:48

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