Month: September 2012

Create a raw disk redirection vmdk in Virtualbox

Posted on by admin

Original Post here.

VBoxManage internalcommands createrawvmdk -filename d:\VMs\gCFRAW.vmdk -rawdisk \\.\PhysicalDrive4

C:\Program Files\Oracle\VirtualBox>VBoxManage internalcommands createrawvmdk -filename d:\VMs\gCFRAW.vmdk -rawdisk \\.\PhysicalDrive4

Oracle VM VirtualBox Command Line Management Interface Version 3.2.8
(C) 2005-2010 Oracle Corporation
All rights reserved.

RAW host disk access VMDK file d:\VMs\gCFRAW.vmdk created successfully.

You can also access specific partitions of host physical disk from VirtualBox, run the same command with additional switches,

VBoxManage internalcommands createrawvmdk -filename c: \Users \sunuser \.Virtualbox \VDI \ mydrive.vmdk -rawdisk \ \. \ PhysicalDrive4 -partitions 1,4

1,4 : are the partitions numbers of PhysicalDrive 0. It will allow you to access the first and fourth partitions of the physical drive.

This command also will create a VMDK file and you can access the drives as explained in first method.

 

mkpasswd on Centos 6.x

Posted on by admin

I happened to need mkpasswd command in CentOS 6.3 minimal:

While there is no package for the tool it can be found in expect command. So run as shown :

yum install expect

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Install Exim on centOS

Posted on by admin

Exim is no longer available as a standard package, but as with most pieces of Linux software, it’s still only a few commands away. If you want to install Exim to use, or just to try, all you need do is:

Install the EPEL (Extra Packages for Enterprise Linux) repository:

wget http://download.fedoraproject.org/pub/epel/6/i386/epel-release-6-5.noarch.rpm
rpm -i epel-release-6-5.noarch.rpm

Install the Exim package

yum install -y exim-mysql

Disable Postfix (the default MTA)

service postfix stop
chkconfig postfix off

Set Exim as the default MTA

alternatives --config mta

And finally start Exim

chkconfig exim on
service exim start

You should now be running Exim, and probably want to visit the official documentation site.

Disable IPv6 in centOS

Posted on by admin
  • Edit /etc/sysconfig/network and set “NETWORKING_IPV6” to “no”
  • For 5.4 and later, replace in /etc/modprobe.conf

 

alias ipv6 off

by

options ipv6 disable=1

Alternative (which might be easier and works on any release with /etc/modprobe.d):

# touch /etc/modprobe.d/disable-ipv6.conf
# echo "install ipv6 /bin/true" >> /etc/modprobe.d/disable-ipv6.conf
  • For CentOS 5.3 or older, add the following to /etc/modprobe.conf :

 

alias ipv6 off
alias net-pf-10 off
  • Run /sbin/chkconfig ip6tables off to disable the IPv6 firewall
  • Reboot the system

<!> With the 5.4 update symbol/ipv6 module dependency capabilities have been introduced; therefore, if IPv6 has been previously disabled as above an upgrade to the bonding driver in 5.4 will result in the bonding kernel module failing to load. For the module to load properly use instead:

# touch /etc/modprobe.d/disable-ipv6.conf
# echo "options ipv6 disable=1" >> /etc/modprobe.d/disable-ipv6.conf

<!> <!> Upstream employee Daniel Walsh recommends not disabling the ipv6 module but adding the following to /etc/sysctl.conf:

net.ipv6.conf.all.disable_ipv6 = 1

In a short way this is what I do:

[root@toro.maranello.local ~]#echo "net.ipv6.conf.all.disable_ipv6 = 1" >> /etc/sysctl.conf

While there I would turn off the IPV6Tables service as well

[root@toro.maranello.local ~]# service ip6tables save
[root@toro.maranello.local ~]# service ip6tables stop
[root@toro.maranello.local ~]# chkconfig ip6tables off

NOTE: SSH x11 forwarding may (and probably will) stop working if you disable the IPv6 …just a heads up :)…

nJoy 😉

Linux prompt tweak ..

Posted on by admin

Just a note for my favorite :

add to the  ~/.bash_profile

PS1="\[\033[35m\]\t\[\033[m\]-\[\033[36m\]\u\[\033[m\]@\[\033[32m\]\h:\[\033[33;1m\]\w\[\033[m\]\$ "

result :

Prompt reloaded
My favorite Linux prompt.

 

Troubleshooting network connection failures VMWare Workstation

Posted on by admin

Symptoms

You are experiencing these issues:

  • No network connectivity for a virtual machine
  • Cannot connect to the Internet from the guest operating system
  • Bridged, Host-only or Network Address Translation (NAT) networking fails

Purpose

This article helps you to determine the cause of networking problems affecting one or more virtual machines. The steps in this article address whether the networking has been misconfigured on the host operating system, guest operating system or virtual machine.

Resolution

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Booting into Single User Mode – (Password Recovery)

Posted on by admin

Many occasions during commissioning of servers we need to reboot especially to freshen hardware re-configurations. (ain’t that still a bitch). Single user mode is there to help.

Booting into single user mode

  1. At the GRUB splash screen at boot time, press any key to enter the GRUB interactive menu.
  2. Select CentOS with the version of the kernel that you wish to boot and type ‘a' to append the line.
  3. Go to the end of the line and type single as a separate word (press the Spacebar and then type single). Press Enter to exit edit mode.
    You are in Single User mode.