How to fix the partitions' number on GPT disk (/dev/sdaX)

Question

I used Gparted to delete EFI (/dev/sda1) and Ubuntu (/dev/sda2) partitions on my secondary drive. The third partition (/dev/sda3) is for data, so I resized it in order to use all unallocated space I've got by deleting the first two partitions. Now, having only a unique partion on the disk, I would like to fix it's number, in order to get /dev/sda1. What's the easiest way to do it that works with a disk having GPT partition table? Thank you!

Answer 1

You may use gdisk to rewrite the partition-table:

sudo gdisk /dev/sda
p  (the p-command prints the recent partition-table on-screen)
s  (the s-command sorts the partition-table entries)
p  (use the p-command again to see the result on your screen)
w  (write the changed partition-table to the disk)
q  (quit gdisk)

You will find most useful information about gdisk at http://www.rodsbooks.com/gdisk/

Answer 2

Intrigued by finding that last link and keen learning something new, I replayed Generoso's partition situation on my system using a 32GB USB drive. Below are my findings, but first my:

Conclusion: As my example is aimed at 1 (final) partition, near the end I merely changed its name. I did not touch the actual sectors. In the link in my comment above, an example is shown where sector number are moved around. I followed that and miserably goofed and destroyed the USB disk, proving how dangerous playing with partitions really is !!
Maybe my scenario also works with multiple partitions, feel free to try it yourself. I dare you to use your primary partition for it.. haha.
Ok, here are my:

Findings: Using Gparted I created 3 partitions, each 1 GB.

# fdisk -l /dev/sdc
Disk /dev/sdc: 30 GiB, 32176472064 bytes, 62844672 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
Disklabel type: dos
Disk identifier: 0xf33657fc

Device     Boot   Start     End Sectors Size Id Type
/dev/sdc1          2048 2099199 2097152   1G 83 Linux
/dev/sdc2       2099200 4196351 2097152   1G 83 Linux
/dev/sdc3       4196352 6293503 2097152   1G 83 Linux

Using Disks to mount partition 3.
Manually placed a file on it.

# ls -l /media/willem/cd4746ac-6d9f-4057-9396-a593ce2f301d/
total 21436
drwx------ 2 root root    16384 May 27 00:12 lost+found
-rw-r--r-- 1 root root 21930117 May 27 00:14 SomeFile.txt

Using Disks to unmount partition 3.
Using Gparted to remove partitions 1 & 2 and grow partition 3 to use the whole disk.

# fdisk -l /dev/sdc
Disk /dev/sdc: 30 GiB, 32176472064 bytes, 62844672 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
Disklabel type: dos
Disk identifier: 0xf33657fc

Device     Boot Start      End  Sectors Size Id Type
/dev/sdc3        8192 62844671 62836480  30G 83 Linux

Using Disks to mount partition 3.
Check the file on partition 3.

# ls -l /media/willem/cd4746ac-6d9f-4057-9396-a593ce2f301d/
total 21436
drwx------ 2 root root    16384 May 27 00:12 lost+found
-rw-r--r-- 1 root root 21930117 May 27 00:14 SomeFile.txt

Using Disks to unmount partition 3.
Copy the partition table from the drive.
Show the partition table.

# sfdisk -d /dev/sdc > sdc.tab
# cat sdc.tab
label: dos
label-id: 0xf33657fc
device: /dev/sdc
unit: sectors

/dev/sdc3 : start=        8192, size=    62836480, type=83

Using vi sdc.tab to change sdc3 into sdc1.
Apply the changed partition table.

# sfdisk --no-reread -f /dev/sdc < sdc.tab
Disk /dev/sdc: 30 GiB, 32176472064 bytes, 62844672 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
Disklabel type: dos
Disk identifier: 0xf33657fc

Old situation:

Device     Boot Start      End  Sectors Size Id Type
/dev/sdc3        8192 62844671 62836480  30G 83 Linux

>>> Script header accepted.
>>> Script header accepted.
>>> Script header accepted.
>>> Script header accepted.
>>> Created a new DOS disklabel with disk identifier 0xf33657fc.
Created a new partition 1 of type 'Linux' and of size 30 GiB.
/dev/sdc2: 
New situation:

Device     Boot Start      End  Sectors Size Id Type
/dev/sdc1        8192 62844671 62836480  30G 83 Linux

The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.

As soon as the command finishes, partition 1 auto-mounts.
Check the file.

# ls -l /media/willem/cd4746ac-6d9f-4057-9396-a593ce2f301d/
total 21436
drwx------ 2 root root    16384 May 27 00:12 lost+found
-rw-r--r-- 1 root root 21930117 May 27 00:14 SomeFile.txt

Using Disks to unmount partition 1.
Done.

PS. I did cat SomeFile.txt every time but I felt it unnecessary to include that output.

Answer 3

You should have resized /dev/sda1 to be bigger than /dev/sda3. Then copy sda3 over sda1. File check sda1 and if no problems, remove sda3, resize sda1 accordingly.