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Vmware Linux Guest Add a New Hard Disk Without Rebooting Guest

admin — Tue, 07 Sep 2010 07:15:38 +0000

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.

Step # 1: 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.

Step # 2: 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 ” > /proc/scsi/scsi

Where,

: Host

: Bus (Channel)

: Target (Id)

: 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
Step #3: 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

Step #4: 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.

Using Ketchup to manage your kernel sources

admin — Tue, 07 Sep 2010 07:44:30 +0000

Today I discovered Ketchup, a little command-line tool to manage your Linux kernel sources. If you’re one of the weirdos, who is still compiling his kernel manually for whatever reason (like I do), I can only recommend it. Ketchup nicely eases up the entire process of checking for updates and applying them to your system.

Let’s not hesitate and look at few usage examples… Want to know what’s the latest version of a particular kernel-tree?

$ ketchup -s 2.6

2.6.17.7

$ ketchup -s 2.6-mm

2.6.18-rc1-mm2

Let’s play with your kernel sources a bit. First of all, you surely want to check what version you currently got lying around…

$ cd /usr/src/linux

$ ketchup -m

2.6.17.6

Let’s assume there is a newer kernel version available and you want to download it, bunzip it, revert the old patch and apply the new one. Nothing easier than that:

# cd /usr/src/linux

# ketchup 2.6-tip

2.6.17.6 -> 2.6.17.7

Applying patch-2.6.17.6.bz2 -R

Applying patch-2.6.17.7.bz2

That’s really it. It will download the patches, revert and apply them, so all you will have to do is watch and wait

Switching to an entirely different kernel versions is just as easy:

# cd /usr/src/linux

# ketchup 2.6.16.2

Final note: If Ketchup should abort with a gpg error, then it couldn’t verify the patch’s or kernel’s signature. Either add the 2.6 public key to your keyring (this is the proper solution) or call Ketchup with an additional -G parameter (this will override signature checking). I’d suggest the former, which is really easy to do by downloading it from a public pgp server:

# gpg --keyserver wwwkeys.pgp.net --recv-keys 0x517D0F0E

Have fun compiling,

Red Hat / CentOS IPv6 Network Configuration

admin — Thu, 26 Aug 2010 04:23:59 +0000

Q. How do I configure static IPv6 networking under RHEL 5.x / Fedora / CentOS Linux?
A. Red Hat / CentOS / Fedora RHEL support IPv6 out of box. All you have to do is update two files and turn on networking.

You need to update and configure following files for IPv6 configuration:

/etc/sysconfig/network : Turn on networking in this file.

/etc/sysconfig/network-scripts/ifcfg-eth0 : Set default IPv6 router IP and server IP address in this file.

Open /etc/sysconfig/network file, enter:
# vi /etc/sysconfig/network
Append following line:

NETWORKING_IPV6=yes

Open /etc/sysconfig/network-scripts/ifcfg-eth0 (1st network config file)
# vi /etc/sysconfig/network-scripts/ifcfg-eth0
Append following config directives for IPv6:

IPV6INIT=yes
IPV6ADDR=
IPV6_DEFAULTGW=

Here is my sample file with mix of IPv4 and IPv6 assigned to eth0:

DEVICE=eth0
BOOTPROTO=static
ONBOOT=yes
HWADDR=00:30:48:33:bc:33
IPADDR=202.54.1.5
GATEWAY=202.54.1.3
NETMASK=255.255.255.248
IPV6INIT=yes
IPV6ADDR=2607:f0d0:1002:0011:0000:0000:0000:0002
IPV6_DEFAULTGW=2607:f0d0:1002:0011:0000:0000:0000:0001

Where,

NETWORKING_IPV6=yes|no – Enable or disable global IPv6 initialization.

IPV6INIT=yes – Enable or disable IPv6 configuration for all interfaces.

IPV6ADDR=2607:f0d0:1002:0011:0000:0000:0000:0002 – Specify a primary static IPv6 address here.

IPV6_DEFAULTGW=2607:f0d0:1002:0011:0000:0000:0000:0001 – Add a default route through specified gateway.

Save and close the file. Restart networking:
# service network restart
Verify your configuration by pinging ipv6 enabled site such as ipv6.google.com:
$ ping6 ipv6.google.com
Sample output:

PING ipv6.google.com(2001:4860:b002::68) 56 data bytes
64 bytes from 2001:4860:b002::68: icmp_seq=1 ttl=59 time=93.2 ms
64 bytes from 2001:4860:b002::68: icmp_seq=2 ttl=59 time=95.0 ms
64 bytes from 2001:4860:b002::68: icmp_seq=3 ttl=59 time=94.2 ms
64 bytes from 2001:4860:b002::68: icmp_seq=4 ttl=59 time=95.2 ms
64 bytes from 2001:4860:b002::68: icmp_seq=5 ttl=59 time=94.8 ms
64 bytes from 2001:4860:b002::68: icmp_seq=6 ttl=59 time=95.1 ms
64 bytes from 2001:4860:b002::68: icmp_seq=7 ttl=59 time=93.3 ms
64 bytes from 2001:4860:b002::68: icmp_seq=8 ttl=59 time=93.8 ms

— ipv6.google.com ping statistics —
8 packets transmitted, 8 received, 0% packet loss, time 7010ms
rtt min/avg/max/mdev = 93.268/94.376/95.268/0.799 ms

Traces path to a network host, enter:
$ traceroute6 ipv6.google.com
Print default IPv6 routing table, enter:
$ route -n -A inet6
Sample output:

Kernel IPv6 routing table
Destination Next Hop Flags Metric Ref Use Iface
::1/128 :: U 0 42531 1 lo
::62.41.14.144/128 :: U 0 0 1 lo
::127.0.0.1/128 :: U 0 0 1 lo
::/96 :: U 256 0 0 sit0
2001:470:1f04:55a::2/128 :: U 0 15201 1 lo
2001:470:1f04:55a::/64 :: U 256 0 0 sit1
fe80::4833:22f4/128 :: U 0 0 1 lo
fe80::212:3fff:fe75:fa0d/128 :: U 0 0 1 lo
fe80::/64 :: U 256 0 0 eth0
fe80::/64 :: U 256 0 0 sit1
ff00::/8 :: U 256 0 0 eth0
ff00::/8 :: U 256 0 0 sit1
::/0 :: U 1 0 0 sit1

How to Speed Your File System

admin — Fri, 22 Jan 2010 08:09:39 +0000

Every time a file is read from your Linux ext3 partition it writes back a attribute to the file detailing the last access time. There are very few programs that actually use this to operate and it slows everything down.

Disabling atime and diratime on your Linux ext3 file systems can improve disk performance up to 40%!

WARNING: If you are using programs such as tmpwatch, mutt, or mail-notify this configuration change could cause those programs that make specific use of atime not to work.

Start a terminal.

Switch to root using the “su -” command.

Backup your fstab – “cp /etc/fstab /etc/fstab.old”.

Open your /etc/fstab in the editor of your choice (nano, kate or gedit recommended). This can be done by issuing the command “nano /etc/fstab”, “kate /etc/fstab”, or “gedit /etc/fstab”.

Locate the partitions that contain your / and /home file systems, as well as any other file system you want to optimize. Examples include /dev/hda2 and /dev/hda3, or /dev/sda2 and /dev/sda3.

In the fourth section (just before the two numbers at the end of the line) you will see the options section of the fstab.

Enter “,noatime,nodiratime” after the existing options for each partition you wish to optimize.

Save the fstab file.

Reboot.

Enjoy your newly optimized Linux ext3 file system. And if you don’t believe it is 40% see this post at kerneltrap.org.

How to umount when the device is busy

admin — Fri, 15 Jan 2010 05:50:28 +0000

You need to unmount a CD or you want to pack away the external drive but when you try to umount it you get the dreaded “device is busy” message. Wouldn’t it be great if Linux actually told you what was keeping the drive busy? Here we are in 2008, I’m using Ubuntu Gutsy, and that message hasn’t changed in all the years I’ve used Linux.

# umount /media/disk/ umount: /media/disk: device is busy umount: /media/disk: device is busy

First thing you’ll do will probably be to close down all your terminals and xterms but here’s a better way. You can use the fuser command to find out which process was keeping the device busy:

# fuser -m /dev/sdc1 /dev/sdc1: 538 # ps auxw|grep 538 donncha 538 0.4 2.7 219212 56792 ? SLl Feb11 11:25 rhythmbox