The Xen Hypervisor Platform
The Xen Hypervisor Platform is comprised of two components – the Xen hypervisor which is responsible for the core hypervisor activities such as CPU, memory virtualization, power management and scheduling of virtual machines.
The Xen hypervisor loads a special, privileged virtual machine called Domain0 or dom0. This virtual machine has direct access to hardware and provides device drivers and I/O management for virtual machines.
Each virtual machine, known as an unprivileged domain or domU, contains a modified Linux kernel that instead of communicating directly with hardware interfaces with Xen hypervisor.
CPU and memory access are handled directly by the Xen hypervisor but I/O is directed to domain 0. The Linux kernel includes “front end” devices for network and block I/O. Requests for I/O are passed to the “back end” process in domain 0 which manages the I/O.
Releasing IP Addresses in WHM/Cpanel
Apache
By default Apache listens to every interface coming into the machine by listening to 0.0.0.0:80/443. Normally you could edit the httpd.conf file directly in order to change the listen line, however that may cause problems with Cpanel’s automation.
To acheive this log into Webhost Manager and find Service Configuration followed by Apache Configuration. Then click on Reserved IPs Editor.
Here you will need to check the boxes of the IP addresses you do NOT wish for Apache to use. Once you save your selections, a new configuration file will be configured to listen on all the other IPs that were not checked. This will allow other services such as alternate web browsers to listen on those IP addresses without conflicting with Apache.
Webhost Manager
Navigate to IP Functions, followed by Show/Edit Reserved IPs. Here you should check the same IPs that were selected in the Apache Reserve list above.
Once this is done WHM/Cpanel will avoid using those IP address when setting up new accounts and services.
Cygwin
Cygwin is a set of powerful tools to assist developers in migrating applications from UNIX/Linux to the Microsoft Windows platform. Cygwin delivers the open source standard Red Hat GNU gcc compiler and gdb debugger on Windows. In addition, it provides for a standard UNIX/Linux development environment on Windows including APIs and command shells. The Cygwin.dll library, included with Cygwin, delivers the interesting subset of UNIX SVR4, BSD, and POSIX APIs to enable quick ports of UNIX/Linux applications to the Windows platform.
Red Hat Cygwin is supported on Windows 2000, XP, 2003 Server, Vista, 2008 Server, 7, and 2008 Server R2. Cygwin is a 32 bit platform that will operate on both 32 and 64 bit Windows installations.
The Red Hat Cygwin official installation utility : ftp://ftp.ges.redhat.com/private/releng/cygwin-1.8/rhsetup.exe
Prepare for a PXE installation
The following steps must be performed to prepare for a PXE installation:
Configure the network (NFS, FTP, HTTP) server to export the installation tree.
Configure the files on the tftp server necessary for PXE booting.
Configure which hosts are allowed to boot from the PXE configuration.
Start the tftp service.
Configure DHCP.
Boot the client, and start the installation.
RPM verification
To display a list of all keys installed for RPM verification run rpm -qa
The output will look similar to the following:
[centos@centos ~]$ sudo rpm -qa gpg-pubkey*
gpg-pubkey-c105b9de-4e0fd3a3
gpg-pubkey-6b8d79e6-3f49313d
[centos@centos ~]$
To check the details run rpm -qi
[centos@centos ~]$ rpm -qi gpg-pubkey-c105b9de-4e0fd3a3
Name : gpg-pubkey Relocations: (not relocatable)
Version : c105b9de Vendor: (none)
Release : 4e0fd3a3 Build Date: Fri 04 Nov 2011 09:37:15 PM IST
Install Date: Fri 04 Nov 2011 09:37:15 PM IST Build Host: localhost
Group : Public Keys Source RPM: (none)
Size : 0 License: pubkey
Signature : (none)
Summary : gpg(CentOS-6 Key (CentOS 6 Official Signing Key) )
Description :
If the GPG key verifies successfully, the command returns gpg OK
[centos@centos ~]$ rpm -K ./Downloads/rpmforge-release-0.5.2-2.el6.rf.x86_64.rpm
./Downloads/rpmforge-release-0.5.2-2.el6.rf.x86_64.rpm: (sha1) dsa sha1 md5 gpg OK
[centos@centos ~]$
