Virt/LinuxGuest

Vmware Linux Guest Add a New Hard Disk Without Rebooting Guest

As a system admin, I need to use additional hard drives for to provide more storage space or to separate system data from user data. This procedure, adding physical block devices to virtualized guests, describes how to add a hard drive on the host to a virtualized guest using VMWare software running Linux as guest.

It is possible to add or remove a SCSI device explicitly, or to re-scan an entire SCSI bus without rebooting a running Linux VM guest. This how to is tested under Vmware Server and Vmware Workstation v6.0 (but should work with older version too). All instructions are tested on RHEL, Fedora, CentOS and Ubuntu Linux guest / hosts operating systems.

Add a New Disk To Vm Guest

First, you need to add hard disk by visiting vmware hardware settings menu. Click on VM > Settings

Fig.01: Vmware Virtual Machine Settings

Alternatively you can press CTRL + D to bring settings dialog box.

Click on Add+ to add new hardware to guest:

Fig.02: VMWare adding a new hardware

Select hardware type Hard disk and click on Next

Fig.03 VMware Adding a new disk wizard

Select create a new virtual disk and click on Next

Fig.04: Vmware Wizard Disk

Set virtual disk type to SCSI and click on Next

Fig.05: Vmware Virtual Disk

Set maximum disk size as per your requirements and click on Next

Fig.06: Finalizing Disk Virtual Addition

Finally, set file location and click on Finish.

Rescan the SCSI Bus to Add a SCSI Device Without rebooting the VM

A rescan can be issued by typing the following command:

echo "- - -" > /sys/class/scsi_host/host#/scan
fdisk -l
tail -f /var/log/message

Sample outputs:

Fig.01:Linux Vmware Rescan New Scsi Disk Without Reboot

Replace host# with actual value such as host0. You can find scsi_host value using the following command:

ls /sys/class/scsi_host

Output:

host0

Now type the following to send a rescan request:

echo "- - -" > /sys/class/scsi_host/host0/scan
fdisk -l
tail -f /var/log/message

Sample Outputs:

Jul 18 16:29:39 localhost kernel:   Vendor: VMware,   Model: VMware Virtual S  Rev: 1.0
Jul 18 16:29:39 localhost kernel:   Type:   Direct-Access                      ANSI SCSI revision: 02
Jul 18 16:29:39 localhost kernel:  target0:0:1: Beginning Domain Validation
Jul 18 16:29:39 localhost kernel:  target0:0:1: Domain Validation skipping write tests
Jul 18 16:29:39 localhost kernel:  target0:0:1: Ending Domain Validation
Jul 18 16:29:39 localhost kernel:  target0:0:1: FAST-40 WIDE SCSI 80.0 MB/s ST (25 ns, offset 127)
Jul 18 16:29:39 localhost kernel: SCSI device sdb: 2097152 512-byte hdwr sectors (1074 MB)
Jul 18 16:29:39 localhost kernel: sdb: Write Protect is off
Jul 18 16:29:39 localhost kernel: sdb: cache data unavailable
Jul 18 16:29:39 localhost kernel: sdb: assuming drive cache: write through
Jul 18 16:29:39 localhost kernel: SCSI device sdb: 2097152 512-byte hdwr sectors (1074 MB)
Jul 18 16:29:39 localhost kernel: sdb: Write Protect is off
Jul 18 16:29:39 localhost kernel: sdb: cache data unavailable
Jul 18 16:29:39 localhost kernel: sdb: assuming drive cache: write through
Jul 18 16:29:39 localhost kernel:  sdb: unknown partition table
Jul 18 16:29:39 localhost kernel: sd 0:0:1:0: Attached scsi disk sdb
Jul 18 16:29:39 localhost kernel: sd 0:0:1:0: Attached scsi generic sg1 type 0
Jul 18 16:29:39 localhost kernel:   Vendor: VMware,   Model: VMware Virtual S  Rev: 1.0
Jul 18 16:29:39 localhost kernel:   Type:   Direct-Access                      ANSI SCSI revision: 02
Jul 18 16:29:39 localhost kernel:  target0:0:2: Beginning Domain Validation
Jul 18 16:29:39 localhost kernel:  target0:0:2: Domain Validation skipping write tests
Jul 18 16:29:39 localhost kernel:  target0:0:2: Ending Domain Validation
Jul 18 16:29:39 localhost kernel:  target0:0:2: FAST-40 WIDE SCSI 80.0 MB/s ST (25 ns, offset 127)
Jul 18 16:29:39 localhost kernel: SCSI device sdc: 2097152 512-byte hdwr sectors (1074 MB)
Jul 18 16:29:39 localhost kernel: sdc: Write Protect is off
Jul 18 16:29:39 localhost kernel: sdc: cache data unavailable
Jul 18 16:29:39 localhost kernel: sdc: assuming drive cache: write through
Jul 18 16:29:39 localhost kernel: SCSI device sdc: 2097152 512-byte hdwr sectors (1074 MB)
Jul 18 16:29:39 localhost kernel: sdc: Write Protect is off
Jul 18 16:29:39 localhost kernel: sdc: cache data unavailable
Jul 18 16:29:39 localhost kernel: sdc: assuming drive cache: write through
Jul 18 16:29:39 localhost kernel:  sdc: unknown partition table
Jul 18 16:29:39 localhost kernel: sd 0:0:2:0: Attached scsi disk sdc
Jul 18 16:29:39 localhost kernel: sd 0:0:2:0: Attached scsi generic sg2 type 0

How Do I Delete a Single Device Called /dev/sdc?

In addition to re-scanning the entire bus, a specific device can be added or existing device deleted using the following command:

echo 1 > /sys/block/devName/device/delete
echo 1 > /sys/block/sdc/device/delete

How Do I Add a Single Device Called /dev/sdc?

To add a single device explicitly, use the following syntax:

echo "scsi add-single-device <H> <B> <T> <L>" > /proc/scsi/scsi

Where,

• <H> : Host
• <B> : Bus (Channel)
• <T> : Target (Id)
• <L> : LUN numbers

For e.g. add /dev/sdc with host # 0, bus # 0, target # 2, and LUN # 0, enter:

echo "scsi add-single-device 0 0 2 0">/proc/scsi/scsi
fdisk -l
cat /proc/scsi/scsi

Sample Outputs:

Attached devices:
Host: scsi0 Channel: 00 Id: 00 Lun: 00
  Vendor: VMware,  Model: VMware Virtual S Rev: 1.0
  Type:   Direct-Access                    ANSI SCSI revision: 02
Host: scsi0 Channel: 00 Id: 01 Lun: 00
  Vendor: VMware,  Model: VMware Virtual S Rev: 1.0
  Type:   Direct-Access                    ANSI SCSI revision: 02
Host: scsi0 Channel: 00 Id: 02 Lun: 00
  Vendor: VMware,  Model: VMware Virtual S Rev: 1.0
  Type:   Direct-Access                    ANSI SCSI revision: 02

Format a New Disk

Now, you can create partition using fdisk and format it using mkfs.ext3 command:

fdisk /dev/sdc
mkfs.ext3 /dev/sdc3

Create a Mount Point And Update /etc/fstab

mkdir /disk3

Open /etc/fstab file, enter:

vi /etc/fstab

Append as follows:

/dev/sdc3               /disk3           ext3    defaults        1 2

Save and close the file.

Optional Task: Label the partition

You can label the partition using e2label. For example, if you want to label the new partition /backupDisk, enter

e2label /dev/sdc1 /backupDisk

Conclusion

The VMware guest now has an additional virtualized storage device. The procedure works for all physical block devices, this includes CD-ROM, DVD and floppy devices. Next, time I will write about adding an additional virtualized storage device using XEN software.