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Creating Software Stacks

The combined tasks of installation and configuration are typically encompassed by the term hardware and software integration. Integration is typically concerned not only with correctly installing and configuring a software product and binding it to a hardware platform, but installing and configuring several software products to correctly function and interoperate with each other. The result of integrating several software products is typically referred to as an integrated software stack, or simply, a software stack.

The use of a software stack helps diminish the total cost of ownership (TCO) of a system. With a software stack, the configured system implements published best practices and site standards that have been validated before the system is deployed in the data center.

The use of a software stack ensures that all such systems are identically configured. This consistency leverages the experiences of the data center personnel. Their experiences on one system are now applicable across many systems. This helps decrease the TCO as well as speeding system recovery in the event of a failure. In the case of a software load, each system must be individually configured by data center personnel. Even if an attempt is made at automating this task, the possibility of human error still exists and system consistency might be lost.

In order to achieve maximum flexibility and robustness of software stacks, a rigorous separation of software installation and configuration information should be maintained at all times.

The SunMC Change Manager uses a customizable flash archive to implement and deploy software stacks. The system that is used as the archetype from which the software stack is created is referred to as the master system.

Selecting the Master System

For most systems, a software stack should be created shortly before the system goes into production. For example, a database server or LDAP server should have its archive created after the database management software has been installed, but before the databases have been created and populated.

Software that stores configuration information outside of a UNIXR file system might not be correctly configured on the flash installed client. For example, logical volume management software like VERITAS Volume Manager (VxVM) or Solstice DiskSuite™ software store metainformation (such as logical volume layout and RAID configuration information) in raw partitions, outside of a file system. Installing a system from a flash archive created on a master machine that uses VxVM with an encapsulated and mirrored boot disk is not possible. Because archive creation does not (and cannot) access the metainformation in the VxVM private regions, any subsequent installation from that archive would be incomplete and unbootable. The configuration of system software such as this is specified by the SunMC Change Manager parameters file. The configuration of software is done by processing this parameters file after the flash archive is installed.

To implement software stacks in a flash archive, create the archive on the master machine after installing all software, but before configuring the software. Using the example of a master machine with a VxVM encapsulated and mirrored boot disk, you would create the flash archive after installing the Solaris OE, after adding VxVM packages, and before executing vxinstall to configure the VxVM software. In this example, you can configure the VxVM installation client, including encapsulating and mirroring the boot disk, from a finish script after the flash archive is installed. The values required to complete this configuration, such as the disk to use as the root mirror, are specified in the parameters file as user defined keyword and value pairs.

Building Software Stacks

When selecting a system to be used as the master system and when building the software stack, pay attention to the types of hardware where the stack will be deployed. All software that might be necessary on the installation clients must be contained in the software stack.

For example, consider a Peripheral Component Interconnect (PCI)-based system selected as a master system. Depending on the choices made at installation time, the SBus driver software might not have been installed. Consequently, any resulting software stacks created from this system will not have the SBus drivers available and any SBus hardware will be unavailable to the installation client.

As another example, consider a flash archive created on a Sun Fire™ 15K domain. In most instances, the domain will not have a graphics frame buffer installed, and consequently, no drivers for any graphic frame buffers. This will not prohibit the flash archive from being correctly deployed onto a wide range of platforms. However, if one of those platforms is a Sun Blade™ 1000 workstation, the graphics monitor and frame buffer will not be available due to the lack of frame buffer drivers in the flash archive. To avoid this issue, either:

  • Ensure that all possible drivers and Solaris OE software that might be needed on any potential client are on the master system (and in the flash archive) or that any missing software is installed from a JumpStart finish script after the flash archive is installed.

  • Or, deploy the software stack to only those systems that are appropriate for that stack.

The first approach is the recommended solution. You can easily install all Solaris OE software by installing the Entire Distribution plus OEM Software (SUNWCXall) package meta-cluster, as well as any third-party or specialized device drivers, on the master system.

Unconfiguring Software

Just as some software applications require specific information and procedures to complete their configuration, some software applications have specific de-installation and unconfiguration procedures. Typically, this unconfiguration can consist of removing host specific information, such as host or device names, from configuration files.

Correctly unconfiguring software might be necessary before creating a flash archive. Unconfiguration is necessary to help ensure that the software stack is completely generalized and does not contain any host specific information from the master system. The procedure of unconfiguring software is commonly referred to as inducing system amnesia.

Inducing System Amnesia

A flash archive created for deployment on many systems needs to be given amnesia—it needs to lose or forget its identity. To induce system amnesia, run the flarcreate(1m) command, which essentially runs the sys-unconfig(1m) command on the master system's flash archive. For most of the Solaris OE, this is sufficient. However, there are a number of other applications that do not register with the use of the sys-unconfig command. (For details, consult the sysidconfig(1m) man page.) A flash archive containing such applications might require additional work to remove traces of the master system's identity before the flash archive is created. A list of items to consider are:

  • Configuration files. Some applications store their configuration information in files, which might not be cleared by the sys-unconfig command. Of particular note are configuration files that contain authentication or authorization information.

  • Log files. Often, applications write identifying information to log files. This might include host names, Internet Protocol (IP) addresses, user names, and so forth. Clean these files to ensure that the clone system does not have log records from the master system. Examples of log files include:

    • /var/adm/lastlog

    • /var/adm/messages.*

    • /var/adm/sulog

  • State files. Some applications might retain state information in files. These could include files used to flag events or configuration files. If application state information is retained in files, reconcile these files on the master system prior to executing the flarcreate command.

  • Backup files. Some applications that modify files create backup copies of the files before modifying them. For example, the useradd(1m) command creates backup copies of the /etc/passwd and /etc/shadow files. If these backup files exist, and if they contain information that identifies the master system, reconcile them.

  • Temporary files. Some applications create temporary files that are intended to be persistent across reboots. These files might be placed in spool directories or in application-specific directories. In particular, exclude the /var/tmp directory from the flash archive or empty it before including it in the flash archive.

  • Queue files. Some applications copy files or data to a queue directory. Examples include the sendmail(1m) file and the Solaris print service. These queue directories are not cleared by sys-unconfig. Clear these directories of data files before creating the flash archive.

  • Mail subsystem files. The sys-unconfig command does not clear the /var/mail directory or user mail files therein. Clear the user mail files from this directory before creating the flash archive.

  • System accounting information. System accounting information might not be cleared by the sys-unconfig command. If this is the case, clear the accounting data from the system accounting directory (typically /var/adm/sa).

It is also important to keep in mind that if any locally developed applications or tools utilize any of the preceding file types, those files must also be cleaned. To help enable locally developed system applications and tools to automatically clean up after themselves on a re-configuration boot, register them with the sysidconfig command. Consult the sysidconfig(1m) man page for details about registering applications.

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