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virtual machines

Server provisioning is nothing but load the Linux or UNIX like operating systems automatically with actual operating systems, device drivers, data, and make a server ready for network operation without any user input. Typically you select a server from a pool of available servers, load the operating systems (such as RHEL, Fedora, FreeBSD, Debian), and finally customize storage, network (IP, gateway, bounding etc), drivers, applications, users etc. Using the following tools you can perform automated unattended operating system installation, configuration, set virtual machines and much more. These software can be used to install a lot (say thousands) of Linux and UNIX systems at the same time.
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By default vSphere does not provide client for Linux or OS X. You need to use Windows system to manage your VMware ESX server. However, it does provides vSphere Web Access which allows you to organize and share virtual machines using web browser. If you try to access vSphere Web Access you may get an error which read as follows:

503 Service Unavailable

You can fix this problem as follows.
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Top 10 Linux Virtualization Software

Virtualization is the latest buzz word. You may wonder computers are getting cheaper every day, why should I care and why should I use virtualization? Virtualization is a broad term that refers to the abstraction of computer resources such as:

  1. Platform Virtualization
  2. Resource Virtualization
  3. Storage Virtualization
  4. Network Virtualization
  5. Desktop Virtualization

This article describes why you need virtualization and list commonly used FOSS and proprietary Linux virtualization software.
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Critical Red Hat Enterprise Linux Kernel Update

Red Hat issued an update version of Linux operating system core called kernel that plugs various security holes for RHEL 5.x. This update has been rated as having important security impact. All users are advised to upgrade kernel package.

Security fixes:

a) A missing capability check was found in the Linux kernel do_change_type routine. This could allow a local unprivileged user to gain privileged access or cause a denial of service. (CVE-2008-2931, Important)

b) A flaw was found in the Linux kernel Direct-IO implementation. This could allow a local unprivileged user to cause a denial of service. (CVE-2007-6716, Important)

c) Tobias Klein reported a missing check in the Linux kernel Open Sound System (OSS) implementation. This deficiency could lead to a possible information leak. (CVE-2008-3272, Moderate)

d) a deficiency was found in the Linux kernel virtual filesystem (VFS) implementation. This could allow a local unprivileged user to attempt file creation within deleted directories, possibly causing a denial of service. (CVE-2008-3275, Moderate)

e) A flaw was found in the Linux kernel tmpfs implementation. This could allow a local unprivileged user to read sensitive information from the kernel. (CVE-2007-6417, Moderate)

Bug fix

a) A kernel crash may have occurred on heavily-used Samba servers after 24 to 48 hours of use.

b) On certain systems, if multiple InfiniBand queue pairs simultaneously fell into an error state, an overrun may have occurred, stopping traffic.

c) With bridging, when forward delay was set to zero, setting an interface to the forwarding state was delayed by one or possibly two timers, depending on whether STP was enabled. This may have caused long delays in moving an interface to the forwarding state. This issue caused packet loss when migrating virtual machines, preventing them from being migrated without interrupting applications.

How do I update my kernel?

Login as root and type:
# uname -mrs
# yum update
# reboot
# uname -mrs

You can easily list all running Virtual machines from a Linux shell prompt without accessing GUI. This is useful to scripts or to get status for any VM.

vmrun is a command line application for controlling various VM operations. Type the following command:
vmrun -T server -h 'https://vmserver.example.com:8333/sdk' -u VMUSERName -p 'yourVMPassword' list
Where,
=> -T server : This is VMWARE server version 2.x

=> -h 'https://vmserver.example.com:8333/sdk' : VMWare server hostname. This can be local or remote server.

=> -u VMUSERName : VMWare server username (usually it is root)

=> -p 'yourVMPassword' : VMWare server password

=> list : List all running vms

List all running VMs

vmrun -T server -h 'https://server.nixcraft.in:8333/sdk' -u root -p 'myPassword' list
Sample output:

Total running VMs: 2
[DISK315k] Debian5/Debian5.vmx
[DISK315k] CentOS52_64/CentOS52_64.vmx

Listing a virtual machine with Workstation on a Windows host (open dos prompt and type the command):
vmrun -T ws list
OR
vmrun -T ws -gu guestUser -gp guestPassword list

Xen is one of the leading Virtualization software. You can use Xen virtualization to implement HA clusters. However, there are few issues you must be aware of while handling failures in a high-availability environment. This article explains configuration options using Xen:

The idea of using virtual machines to build high available clusters is not new. Some software companies claim that virtualization is the answer to your HA problems, off course that's not true. Yes, you can reduce downtime by migrating virtual machines to another physical machine for maintenance purposes or when you think hardware is about to fail, but if an application crashes you still need to make sure another application instance takes over the service. And by the time your hardware fails, it's usually already too late to initiate the migration.

So, for each and every application you still need to look at whether you want to have it constantly available, if you can afford the application to be down for some time, or if your users won't mind having to relogin when one server fails.

=> Using Xen for High Availability Clusters [onlamp.com]

Download of the day: Oracle VM

Virtualization is the process of abstracting computing resources such that multiple operating system and application images can share a single physical server, bringing significant cost-of-ownership and manageability benefits. Through its Oracle VM product, Oracle offers scalable, low-cost server virtualization for heterogeneous applications.

Oracle VM is free server virtualization software that fully supports both Oracle and non-Oracle applications, and is three times more efficient than other server virtualization products.
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