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Chapter 9 . Configuring the System with YaST 265 Further Information The author of AutoYaST is Anas Nashif of SUSE; the main documentation for it is located at www.suse.com/~nashif/autoinstall/. There is an active mailing list at suse-autoinstall. To subscribe to the list, send an empty mail to suse-autoinstallsubscribe@suse.com, or use the form at www.suse.com/en/ private/support/online_help/mailinglists/. SUSE s AutoYaST is an extremely powerful tool for automatic installation and is difficult conceptually. But it is certainly worth looking at and can be very useful in various Enterprise scenarios, including the easy deployment of desktop systems and the installation of nodes in clusters, to name but two. …
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264 Part II . The SUSE System Figure 9-41: Editing the control file with emacs Using Pre-Install, chroot, and Post-Install scripts AutoYaST enables you to include scripts in the XML file (as CDATA sections). The three phases of the installation at which the scripts can be run are: before the installation proper begins (pre-scripts); while the installation system is in memory, but before the first reboot (chrootscripts); and after the first reboot of the system (post-scripts). Using such scripts, which are usually shell scripts, means that essentially anything is possible. For example, during the main part of the installation, the hard disk partition to which the packages are being written is mounted in the installation system on /mnt, so during this phase you can use a script to copy additional packages or files across the network from the installation server and into /mnt/tmp. After the first boot, this directory will be /tmp. A post-script can be used to install, copy, or manipulate the files in any way that might be required. By such methods, any kind of configuration that is not allowed for in YaST can be done automatically as part of the autoinstallation server, and the only limit on this process is your own ingenuity.
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Chapter 9 . Configuring the System with YaST 263 Figure 9-39: Creating a reference file based on the current machine Figure 9-40: Viewing the XML source
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262 Part II . The SUSE System Figure 9-38: YaST s AutoYaST module main screen The module enables you to create a configuration by going through any or all of the possible steps that would be taken during a real installation, using an interface almost identical to YaST during installation. Alternatively, you can create a configuration based on the current machine, which you can use as a starting point or template for your XML files (see Figure 9-39). Here you can choose which aspects of the current machine s configuration you want to copy to the reference profile. You can then base your final configuration on this by making suitable changes. You can at any stage view the XML file itself or go through the elements of an interactive installation and modify the file (see Figure 9-40). When you have a basic XML file, you may want to refine it by editing it by hand (see Figure 9-41); this can be done with the emacseditor with the psgmlspackage installed. This makes emacsa true XML editor, which can find and parse the XML DTD and help you in many ways to avoid creating an invalid file.
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Chapter 9 . Configuring the System with YaST 261 XML file allows for a very high degree of detailed control over the installation of the particular machine: Different machines can have different specific XML control files. Essentially, the XML file contains an answer to every question that the installer asks the user in an interactive installation. Mode of Operation The machine that is being installed has to be booted somehow. The possibilities are to boot it from a floppy disk, from a bootable CD-ROM, or by PXE network booting. . SUSE provides a GRUB boot floppy for starting an installation that is capable of network booting in conjunction with a Trivial FTP (TFTP) or Dynamic Host Configuration Protocol (DHCP) server. . Alternatively, the system can be booted from an installation CD, but can be given a boot parameter such as install=nfs://192.168.1.1/suse-install/. If a DHCP server is available, the machine obtains an IP address and then finds the installation files from the information given at boot time. This information can also be placed in an info file held on a floppy disk to be read at the start of the installation. . The most elegant method, if it is available, is PXE booting (supported by most modern hardware). In this case, a little more is needed on the installation server side: You need to run a DHCP server and a TFTP server together with the special files (from the package pxe) required to start the boot process. The DHCP server offers an IP address based on the client s hardware address; the TFTP server then gives a file based on the IP address, which references the XML installation control file on the server. In any of these cases, when the installer has booted and obtained the relevant XML file, the XML file controls the rest of the installation just as if a human were interacting with the installer. The installation server can offer the installation files by HTTP, NFS, or FTP. In the case of SUSE Professional, it is sufficient that the contents of the installation CDs or DVD (or a mirror of the installation set on the FTP site) be available by one of these methods. The YaST Autoinstallation Module The purpose of this module is to help you create the AutoYaST XML control file. You can start the module with: # yast2 autoyast or by selecting the icon in the YaST Misc screen (the one with the wonderful pineapple icon). When you start the module you will see a screen like Figure 9-38.
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260 Part II . The SUSE System Installing from the Installation Server Assuming that you have set up an installation server as described previously and it is available on the network, you can install a new client from it very easily. Ideally there should be a DHCP server on the network (see Chapter 20). Then when the client boots, it will get an address and will be able to see the installation source directly without further intervention. If the new machine is booted from the standard SUSE installation media, the first screen you see will offer a set of choices (by pressing F3) for the source to use. These include NFS, FTP, HTTP, local directory, and so on. If you set up the installation source with SLP, and if a DHCP server exists on the network, then everything is easy. In the first screen, select SLP, choose Installation, and as soon as the machine gets an IP address, it will also find any SUSE installation servers that are available on the network by SLP. You will then be asked the select the one you want and the rest of the installation will be done from the installation server. Autoinstallation AutoYaST A common scenario is the need to install the operating system on a number of machines in an identical way or perhaps in a predefined way. Where the hardware is exactly identical, it can sometimes be simplest to use the ghosting approach: copying an image of one hard disk to all the others. However, it may well be that there are significant differences between the machines, but you want to install a known set of packages on each, possibly with some other predefined configuration. In such a case, automatic installation may well be the best approach. Another way of looking at this is the well-known dictum that if you find yourself repeating a task more than a few times, the best thing to do is to find a way of automating the task. That is exactly what SUSE has done by providing the ability to do automated installations with YaST: the AutoYaST method. Principles Provided you have a means of booting a machine that you are trying to install, and if at the same time you can tell it where to find the installation set, the rest of the installation can be done across the network. If at the same time you can tell the installer the answer to each and every question in the interactive installation, the installation would be truly unattended and automated. AutoYaST does exactly this: It is a highly configurable method of implementing automated, unattended network installations. The details of the installation required for each machine are held in an XML file on the installation server. The
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Chapter 9 . Configuring the System with YaST 259 Figure 9-36: Konqueror displaying SLP information If you click on the YaST Installation source icon, you will see a window similar to the one in Figure 9-37. Figure 9-37: Konqueror showing details of the SLP installation source
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258 Part II . The SUSE System You are offered three choices for how you want to offer the installation source across the network: you can make it available by HTTP, FTP, or NFS. In the module itself these are mutually exclusive choices, but there is no reason why you could not offer the sources by more than one of these protocols. However, there would be some extra manual setup required to do so. The choice of which protocol to use depends on your circumstances. If the installation server is not on the same network as the clients that are to be installed, then HTTP or FTP (which can be accessed through a proxy) are the likely choice. If the installation server is on the same network and directly accessible by the clients, then NFS is probably the right answer. In Figure 9-35, we have chosen NFS, and we have selected a location where the installation set is going to be created (/instserv/10.0/). You are then asked for a name for the installation source (a server may be advertising more than one source, so it is necessary for each to have an individual name this will also be the name given to the directory in which the sources are placed). You can either use the installation CDs or DVD to create the installation source, or, if you have ISO images available, YaST can create it from those. Service Packs can also be integrated into the installation source if they exist. The same screen offers the option Announce as Installation Server with SLP. When you select this option, the installation server will use SLP to announce itself on the network, making the installation process simpler on the clients as described previously. You will then be prompted for the installation media (CDs or DVDs, or if you opted to use ISO images, you will be prompted for the path to find those images on the hard disk). You will be prompted to change the media until the installation source has been completed. The necessary NFS, FTP, or HTTP server will be set up or modified automatically for you, and will be started automatically. When the process is complete, if you go to a Konqueror window on the local machine or elsewhere on the network and type the location slp:/, you will see a window similar to the one in Figure 9-36. This window provides a description of the SLP source being offered. It is, of course, possible that you might have more than one SUSE installation source advertising itself by SLP on the network.
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Chapter 9 . Configuring the System with YaST 257 . The YaST installation server module . The use of SLP (Service Location Protocol) Service Location Protocol allows services to advertise themselves across the network and be discovered by clients. In the case of the installation server, this means that the client machine that is being installed can discover any installation server on the network without the need to type in an IP number or directory designation. All that is required is that when you start the installation on the client, you choose SLP as the source (rather than the other alternatives such as CD, NFS, local disk, and so on). The client will then discover the installation server and access the installation source through whatever protocol it is being offered, without further manual intervention. Setting Up an Installation Server The package name of YaST module that simplifies the process of setting up an installation server is yast2-instserver. This is not installed by default, so the first thing you will need to do if you want to use it is to install it in the usual way. Once installed, the module can be started from the Misc section of YaST, or using the command yast2 instserver You will see the screen in Figure 9-35. Figure 9-35: YaST installation server: initial screen
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256 Part II . The SUSE System YOU Dangers It is important to realize that if for some reason you have installed third-party versions of packages having the same name as SUSE packages, a careless YOU update could overwrite them. When running a mission-critical system, although you should always be aware of security issues and be ready to apply relevant security patches to any publicly available machine as a matter of priority, you should also be extremely careful not to apply all patches without serious thought. Some kernel patches in particular can totally break the functionality of third-party commercial software, which may at best mean that you need to reconfigure the software and at worst could lead to a situation where you have real difficulty in getting back to a working system. The online_update command The command online_update can be used for a noninteractive update. However, the previous comments about the dangers of careless updating apply even more to this procedure because it does not allow you to select and deselect patches. Running the command with the -h option (online_update-h) will give a list of options. fou4s Fast Online Updater for SUSE (fou4s) from http://fou4s.gaugusch.at/ is another command-line alternative to YOU. It has similar functionality, but claims additional speed and can be run either interactively or automatically from a script or cron job. The YaST Installation Server Module An installation server is a machine that offers the installation set across the network. If you are likely to want to install a large number of machines, this gives you a way of reducing the amount of work involved in installing systems; after the new system has been booted, it can access the installation set across the network, and the bulk of the installation can be done unattended. If you set up autoinstallation (see the next section) and network booting, then the installations can in fact be totally automatic. There are two features that were introduced by SUSE at the time of the release of SLES 9 that make these processes easier than they were before. In the past, it was necessary to create and populate the directories on the installation server manually with materials from the installation CDs. It was also necessary to manually set up NFS, FTP, or HTTP serving for those directories. When performing an installation across the network, it was also necessary to select the installation source manually. The two features that make the whole process easier are:
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