vSphere: Hot Add or Remove a VMDK with a Linux VM

By Arne Fokkema - ICT-Freak.nl

In this post I will show you how to hot add a new VMDK to a Linux VM. I will also post how to remove a VMDK if necessary.

Hot Add a new VMDK

Add the new VMDK:

After you added the new VMDK login to the VM and run fdisk –l

[root@nagios ~]#  fdisk -l

Disk /dev/sda: 21.4 GB, 21474836480 bytes
255 heads, 63 sectors/track, 2610 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          13      104391   83  Linux
/dev/sda2              14        2610    20860402+  8e  Linux LVM

The new disk isn’t available yet so we have to do a SCSI bus rescan. You can run the following command to do a rescan:

echo "- – -">/sys/class/scsi_host/host0/scan

When you run the fdisk –l command after the rescan, you will see the new disk.

[root@nagios ~]# fdisk -l

Disk /dev/sda: 21.4 GB, 21474836480 bytes
255 heads, 63 sectors/track, 2610 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          13      104391   83  Linux
/dev/sda2              14        2610    20860402+  8e  Linux LVM

Disk /dev/sdb: 10.7 GB, 10737418240 bytes
255 heads, 63 sectors/track, 1305 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Disk /dev/sdb doesn’t contain a valid partition table

The new disk doesn’t contain a valid parition table. This can be fixed with running the fdisk /dev/sdb command:

fdisk –l /dev/sdb n p 1 1 {enter} x b 1 128 w q

The options x b 1 128 will align the new parition.  For more info about, see Bob Plankers his post here: http://lonesysadmin.net/2010/03/30/i-will-keep-saying-it-align-your-partitions/

Now we have a valid parition table but no file system. Run the mkfs.ext3 /dev/sdb1 command to accomplish this task:

[root@nagios ~]# mkfs.ext3 /dev/sdb1
mke2fs 1.39 (29-May-2006)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
1310720 inodes, 2620595 blocks
131029 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=2684354560
80 block groups
32768 blocks per group, 32768 fragments per group
16384 inodes per group
Superblock backups stored on blocks:
        32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632

Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 39 mounts or
180 days, whichever comes first.  Use tune2fs -c or -i to override.

Run the fdisk –l command to verify the new configuration:

[root@nagios ~]# fdisk -l

Disk /dev/sda: 21.4 GB, 21474836480 bytes
255 heads, 63 sectors/track, 2610 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          13      104391   83  Linux
/dev/sda2              14        2610    20860402+  8e  Linux LVM

Disk /dev/sdb: 10.7 GB, 10737418240 bytes
255 heads, 63 sectors/track, 1305 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1        1305    10482381   83  Linux

if you want to auto mount the new disk, you have to create a new folder and add an entry to the /etc/fstab file.

mkdir /disk2
nano or vi /etc/fstab

add the following line:
/dev/sdb1               /disk2                  ext2    defaults        1 2

Now you are ready to mount the new disk.

mount /dev/sdb1 /disk2/

These are all the steps.

Hot Remove a VMDK

If you want to remove an extra VMDK from a Linux VM,you need to follow these steps.

First you need to unmount the /dev/sdb1:

umount /dev/sdb1

Remove the /disk2 folder:

rmdir /disk2/

Remove the entry from the /etc/fstab:

nano or vi /etc/fstab

remove the following line:
/dev/sdb1               /disk2                  ext2    defaults        1 2

Delete the device:

echo 1 > /sys/block/sdb1/device/delete

Remove the VMDK: