#fdisk /dev/loop1

Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel
Building a new DOS disklabel with disk identifier 0xb08059ca.
Changes will remain in memory only, until you decide to write them.
After that, of course, the previous content won't be recoverable.
The number of cylinders for this disk is set to 2610.
There is nothing wrong with that, but this is larger than 1024,
and could in certain setups cause problems with:
1) software that runs at boot time (e.g., old versions of LILO)
2) booting and partitioning software from other OSs
   (e.g., DOS FDISK, OS/2 FDISK)
Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)
Command (m for help): n
Command action
   e   extended
   p   primary partition (1-4)
p
Partition number (1-4): 4
First cylinder (1-2610, default 1):
Using default value 1
Last cylinder or +size or +sizeM or +sizeK (1-2610, default 2610):
Using default value 2610
Command (m for help): p
Disk /dev/loop1: 21.4 GB, 21475885056 bytes
255 heads, 63 sectors/track, 2610 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0xb08059ca
      Device Boot      Start         End      Blocks   Id  System
/dev/loop1p4               1        2610    20964793+  83  Linux
Command (m for help): d
Selected partition 4
Command (m for help): p
Disk /dev/loop1: 21.4 GB, 21475885056 bytes
255 heads, 63 sectors/track, 2610 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0xb08059ca
      Device Boot      Start         End      Blocks   Id  System
Command (m for help): n
Command action
   e   extended
   p   primary partition (1-4)
p
Partition number (1-4): 1
First cylinder (1-2610, default 1):
Using default value 1
Last cylinder or +size or +sizeM or +sizeK (1-2610, default 2610):
Using default value 2610
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
WARNING: Re-reading the partition table failed with error 22: Invalid argument.
The kernel still uses the old table.
The new table will be used at the next reboot.
Syncing disks.