Formatting a Boot Partition in RHEL or CentOS 6.8 in Azure

Format the new partition with ext4 or ext3. For example:

# mkfs.ext4 /dev/sda2

The files from the /boot directory should be copied to the new boot partition:

# mkdir -p /tmp/sda2
# mount /dev/sda2  /tmp/sda2
# cp -a /boot/* /tmp/sda2

Find the UUID of the new boot partition:

# blkid /dev/sda2
# umount /tmp/sda2

Add an entry to /etc/fstab to mount the new boot partition, like this:

UUID=<uuid> /boot ext4 rw 0 0

Important: Mount the /boot partition. For example:

# mount /boot

Re-install GRUB on the current boot device (GRUB files need to be copied to /boot, which was mounted in the previous step). For example:

# grub-install /dev/sda

Note that GRUB is being installed on /dev/sda but the boot directory comes from /dev/sda2.

In CentOS 6.8, grub is installed, and not grub2. CentOS 6.8 does not provide a utility to update the /boot/grub/grub.conf file, so you need to update it manually.

The original grub.conf file, before modification, follows. The highlighted text indicates what will need to be changed:

default=0
timeout=5
splashimage=(hd0,0)/boot/grub/splash.xpm.gz
hiddenmenu
title CentOS 6 (2.6.32-642.1.1.el6.x86_64)
   root (hd0,0)
   kernel /boot/vmlinuz-2.6.32-642.1.1.el6.x86_64 ro root=UUID=8b9b4465-bdbf-4780-8b1e-d5b4d089a77d rd_NO_LUKS  KEYBOARDTYPE=pc KEYTABLE=us LANG=en_US.UTF-8 rd_NO_MD SYSFONT=latarcyrheb-sun16 console=ttyS0,115200n8 earlyprintk=ttyS0,115200 rootdelay=300 rd_NO_LVM rd_NO_DM
   initrd /boot/initramfs-2.6.32-642.1.1.el6.x86_64.img

The modified grub.conf file follows, with highlighted text for the lines that are changed:

default=0
timeout=5
splashimage=(hd0,0)/boot/grub/splash.xpm.gz
hiddenmenu
title CentOS 6 (2.6.32-642.1.1.el6.x86_64)
   root (hd0,1)
   kernel /vmlinuz-2.6.32-642.1.1.el6.x86_64 ro root=UUID=8b9b4465-bdbf-4780-8b1e-d5b4d089a77d rd_NO_LUKS  KEYBOARDTYPE=pc KEYTABLE=us LANG=en_US.UTF-8 rd_NO_MD SYSFONT=latarcyrheb-sun16 console=ttyS0,115200n8 earlyprintk=ttyS0,115200 rootdelay=300 rd_NO_LVM rd_NO_DM
   initrd /initramfs-2.6.32-642.1.1.el6.x86_64.img

There are a total of three modifications:

Change 0 to 1 in the root line:(hd0,0) becomes (hd0,1)
Remove /boot from the kernel line and the initrd line.

Reboot the system and make sure that it boots properly from the new boot partition.