Preparing the Azure VM

We highly recommend that you set the access method to ssh public key. If you lose VM access during the encryption set up procedures, the only reliable access method is ssh public key. To do so:
1. Log into the Azure Resource Manager (ARM).
2. Click Virtual Machine.
3. Click the +Add button at the top left.
4. On the next tab, select the machine you want to access.
5. Set the deployment model to Resource Manager and then set SSH public key.
6. Deploy the VM as normal.
Release the OS disk from the VM. To do this, you must delete the VM from Azure.
1. Make a note of all required customizations, such as as Resource Name, Storage Account name, VHD disk file name, Diagnostics storage account name, and so on. All customizations will be lost when you delete the VM.
2. Delete the VM and wait for notification that the deletion is complete.
Create another VM in the same Resource Group and the same Location. This VM needs to be able to see the OS disk on the original VM, because Linux does not support the online resize of a mounted file system.

In our examples we will call this newly created VM /dev/sdc3.

Attach the OS disk to the new VM. To do so:

Click the Virtual machines tab and select the new VM to which you want to add the OS disk from the original VM.
Click the Disk tab, then click Attach existing.
Select Storage Account > VHD, then select the VHD file of the original VM.
Set Host caching to Read/Write. The OS disk now shows on the new VM, where you can use dmesg to find out the device name. In the case of a new Ubuntu 14.04 server, it shows as /dev/sdc.

Resize the root file system on this device to create enough space for a separate boot partition. For example:

Mount the root partition:

# mkdir /tmp/root
# mount -o ro /dev/sdc1 /tmp/root

Find out the space required by /boot subtree,

# du -sh /tmp/root/boot
178M    /tmp/root/boot
# umount /tmp/root

The new boot partition should at least have two times the amount of space used by /boot.

The following three steps are required to shrink the original root file system and create a new /boot partition.

# e2fsck -f /dev/sdc1
# resize2fs /dev/sdc1 <newsize>
# fdisk -u /dev/sdc

Note: Assuming that the size of /dev/sdc1 is 10 GB originally, we have to cut out 500 MB (Considering max size of /boot) from it. The following is the example of the resize2fs command:

# resize2fs /dev/sdc1 9G

Here, the filesystem size will get reduced by 1 GB, out of which 500 MB will be allocated to /boot.

We will have to delete and recreate the root partition, ensure that the new root partition starts at exactly the same block, and that its size is equal to or greater than the new size of the root file system (after we have run resize2fs). As a rule of thumb, the size of the new root partition should be 100 MB more than new size of the root file system. Remember to set the boot flag on the root partition.

Here is the actual output on a test machine:

root@prmub1604:~# e2fsck -f /dev/sdc1
e2fsck 1.42.13 (17-May-2015)
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
/dev/sdc1: 11/655360 files (0.0% non-contiguous), 79663/2621184 blocks
			
root@prmub1604:~# resize2fs /dev/sdc1 9G
resize2fs 1.42.13 (17-May-2015)
Resizing the filesystem on /dev/sdc1 to 2359296 (4k) blocks.
The filesystem on /dev/sdc1 is now 2359296 (4k) blocks long.

root@prmub1604:~# fdisk -u /dev/sdc

Welcome to fdisk (util-linux 2.27.1).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.

Command (m for help): p
Disk /dev/sdc: 10 GiB, 10737418240 bytes, 20971520 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: dos
Disk identifier: 0x3795c63b

Device     Boot Start      End  Sectors Size Id Type
/dev/sdc1        2048 20971519 20969472  10G 83 Linux

Command (m for help): d
Selected partition 1
Partition 1 has been deleted.

Command (m for help): p
Disk /dev/sdc: 10 GiB, 10737418240 bytes, 20971520 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: dos
Disk identifier: 0x3795c63b

Command (m for help): n
Partition type
   p   primary (0 primary, 0 extended, 4 free)
   e   extended (container for logical partitions)
Select (default p): p
Partition number (1-4, default 1): 1
First sector (2048-20971519, default 2048): 2048 
Last sector, +sectors or +size{K,M,G,T,P} (2048-20971519, default 20971519): +9G
Created a new partition 1 of type 'Linux' and of size 9 GiB.

Command (m for help): p
Disk /dev/sdc: 10 GiB, 10737418240 bytes, 20971520 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: dos
Disk identifier: 0x3795c63b

Device     Boot Start      End  Sectors Size Id Type
/dev/sdc1        2048 18876415 18874368   9G 83 Linux

Command (m for help): n
Partition type
   p   primary (1 primary, 0 extended, 3 free)
   e   extended (container for logical partitions)
Select (default p): p
Partition number (2-4, default 2): 2
First sector (18876416-20971519, default 18876416): 18876416
Last sector, +sectors or +size{K,M,G,T,P} (18876416-20971519, default 20971519): +500M

Created a new partition 2 of type 'Linux' and of size 500 MiB.

Command (m for help): p
Disk /dev/sdc: 10 GiB, 10737418240 bytes, 20971520 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: dos
Disk identifier: 0x3795c63b

Device         Boot    Start      End    Sectors  Size Id Type
/dev/sdc1      2048 18876415 18874368    9G 83         Linux
/dev/sdc2      18876416 19900415  1024000  500M 83     Linux

Command (m for help): a
Partition number (1,2, default 2): 1

The bootable flag on partition 1 is enabled now.

Command (m for help): p
Disk /dev/sdc: 10 GiB, 10737418240 bytes, 20971520 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: dos
Disk identifier: 0x3795c63b

Device     Boot    Start      End  Sectors  Size Id Type
/dev/sdc1  *        2048 18876415 18874368    9G 83 Linux
/dev/sdc2       18876416 19900415  1024000  500M 83 Linux

Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.
root@prmub1604:~#

Now we have two partitions on the same disk: one is with 9 GB, and another for /boot with 500 MB.

What to Do Next

Recreate the VM in Azure and make a template from the VM as described in Recreating the VM in Azure.

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