| Installation GuideChapter 31. Installing Through VNCThe Red Hat Enterprise Linux installer (anaconda) offers you two interactive modes of operation. The original mode is a text-based interface. The newer mode uses GTK+ and runs in the X Window environment. This chapter explains how you can use the graphical installation mode in environments where the system lacks a proper display and input devices typically associated with a workstation. This scenario is typical of systems in datacenters, which are often installed in a rack environment and do not have a display, keyboard, or mouse. Additionally, a lot of these systems even lack the ability to connect a graphical display. Given that enterprise hardware rarely needs that ability at the physical system, this hardware configuration is acceptable. Even in these environments, however, the graphical installer remains the recommended method of installation. The text mode environment lacks a lot of capabilities found in the graphical mode. Many users still feel that the text mode interface provides them with additional power or configuration ability not found in the graphical version. The opposite is true. Much less development effort is put in to the text-mode environment and specific things (for example, LVM configuration, partition layout, package selection, and bootloader configuration) are deliberately left out of the text mode environment. The reasons for this are: Less screen real estate for creating user interfaces similar to those found in the graphical mode. Difficult internationalization support. Desire to maintain a single interactive installation code path.
Anaconda therefore includes a Virtual Network Computing (VNC) mode that allows the graphical mode of the installer to run locally, but display on a system connected to the network. Installing in VNC mode provides you with the full range of installation options, even in situations where the system lacks a display or input devices. Performing a VNC installation requires a VNC viewer running on your workstation or other terminal computer. Locations where you might want a VNC viewer installed: VNC is open source software licensed under the GNU General Public License. VNC clients are available in the repositories of most Linux distributions. Use your package manager to search for a client for your chosen distribution. For example, on Red Hat Enterprise Linux, install the tigervnc package: # yum install tigervnc Once you have verified you have a VNC viewer available, it's time to start the installation. 31.2. VNC Modes in AnacondaAnaconda offers two modes for VNC installation. The mode you select will depend on the network configuration in your environment. Direct mode VNC in anaconda is when the client initiates a connection to the VNC server running in anaconda. Anaconda will tell you when to initiate this connection in the VNC viewer. Direct mode can be activated by either of the following commands: When you activate VNC mode, anaconda will complete the first stage of the installer and then start VNC to run the graphical installer. The installer will display a message on the console in the following format: Running anaconda VERSION, the PRODUCT system installer - please wait... Anaconda will also tell you the IP address and display number to use in your VNC viewer. At this point, you need to start the VNC viewer and connect to the target system to continue the installation. The VNC viewer will present anaconda to you in graphical mode. There are some disadvantages to direct mode, including: Requires visual access to the system console to see the IP address and port to connect the VNC viewer to. Requires interactive access to the system console to complete the first stage of the installer.
If either of these disadvantages would prevent you from using direct mode VNC in anaconda, then connect mode is probably more suited to your environment. Certain firewall configurations or instances where the target system is configured to obtain a dynamic IP address may cause trouble with the direct VNC mode in anaconda. In addition, if you lack a console on the target system to see the message that tells you the IP address to connect to, then you will not be able to continue the installation. The VNC connect mode changes how VNC is started. Rather than anaconda starting up and waiting for you to connect, the VNC connect mode allows anaconda to automatically connect to your view. You won't need to know the IP address of the target system in this case. To activate the VNC connect mode, pass the vncconnect boot parameter: boot: linux vncconnect=HOST Replace HOST with your VNC viewer's IP address or DNS host name. Before starting the installation process on the target system, start up your VNC viewer and have it wait for an incoming connection. Start the installation and when your VNC viewer displays the graphical installer, you are ready to go. 31.3. Installation Using VNCNow that you have installed a VNC viewer application and selected a VNC mode for use in anaconda, you are ready to begin the installation. 31.3.1. Installation ExampleThe easiest way to perform an installation using VNC is to connect another computer directly to the network port on the target system. The laptop on a datacenter crash cart usually fills this role. If you are performing your installation this way, make sure you follow these steps: Connect the laptop or other workstation to the target system using a crossover cable. If you are using regular patch cables, make sure you connect the two systems using a small hub or switch. Most recent Ethernet interfaces will automatically detect if they need to be crossover or not, so it may be possible to connect the two systems directly using a regular patch cable. Configure the VNC viewer system to use a RFC 1918 address with no gateway. This private network connection will only be used for the purpose of installation. Configure the VNC viewer system to be 192.168.100.1/24. If that address is in use, just pick something else in the RFC 1918 address space that is available to you. Start the installation on the target system. Booting the installation DVD. If booting the installation DVD, make sure vnc is passed as a boot parameter. To add the vnc parameter, you will need a console attached to the target system that allows you to interact with the boot process. Enter the following at the prompt: boot: linux vnc Boot over the network. If the target system is configured with a static IP address, add the vnc command to the kickstart file. If the target system is using DHCP, add vncconnect=HOST to the boot arguments for the target system. HOST is the IP address or DNS host name of the VNC viewer system. Enter the following at the prompt: boot: linux vncconnect=HOST
When prompted for the network configuration on the target system, assign it an available RFC 1918 address in the same network you used for the VNC viewer system. For example, 192.168.100.2/24. This IP address is only used during installation. You will have an opportunity to configure the final network settings, if any, later in the installer. Once the installer indicates it is starting anaconda, you will be instructed to connect to the system using the VNC viewer. Connect to the viewer and follow the graphical installation mode instructions found in the product documentation.
31.3.2. Kickstart ConsiderationsIf your target system will be booting over the network, VNC is still available. Just add the vnc command to the kickstart file for the system. You will be able to connect to the target system using your VNC viewer and monitor the installation progress. The address to use is the one the system is configured with via the kickstart file. If you are using DHCP for the target system, the reverse vncconnect method may work better for you. Rather than adding the vnc boot parameter to the kickstart file, add the vncconnect=HOST parameter to the list of boot arguments for the target system. For HOST, put the IP address or DNS host name of the VNC viewer system. See the next section for more details on using the vncconnect mode. 31.3.3. Firewall ConsiderationsIf you are performing the installation where the VNC viewer system is a workstation on a different subnet from the target system, you may run in to network routing problems. VNC works fine so long as your viewer system has a route to the target system and ports 5900 and 5901 are open. If your environment has a firewall, make sure ports 5900 and 5901 are open between your workstation and the target system. In addition to passing the vnc boot parameter, you may also want to pass the vncpassword parameter in these scenarios. While the password is sent in plain text over the network, it does provide an extra step before a viewer can connect to a system. Once the viewer connects to the target system over VNC, no other connections are permitted. These limitations are usually sufficient for installation purposes. Be sure to use a temporary password for the vncpassword option. It should not be a password you use on any systems, especially a real root password. If you continue to have trouble, consider using the vncconnect parameter. In this mode of operation, you start the viewer on your system first telling it to listen for an incoming connection. Pass vncconnect=HOST at the boot prompt and the installer will attempt to connect to the specified HOST (either a hostname or IP address). |
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