| Patching provides a means for software providers to fix their programs by updating some or all of their code. While this also includes third-party software, suppliers are likely to use their own mechanism for patching their software, so it is normally used to relate to the operating system components only. For this reason, in this chapter we'll just look at patching Solaris and the mechanism used by Sun to do this. Patches are administered using the patchadd and patchrm commands, or the (older) installpatch and backoutpatch programs. Patchadd and patchrm are supplied with the operating system and are the recommended way to administer patches, while installpatch and backoutpatch are the original programs that were, and still are, supplied with the patch itself, although they will be removed at some point in the future. Patches are actually based on the package format, which means that patchadd and patchrm use pkgadd and pkgrm, respectively, to install or remove patches as required. They are numbered in a way that identifies both the patch itself and the particular revision of the patch. The naming convention used is <patch number>-<patch revision>. For example, 101580-09 would be revision 9 of patch 101580. Each patch file is delivered with a README file that contains important information such as the bugs that are fixed (along with the bug numbers), a list of the packages that are affected, the files to be installed, which other patches are required for this one to work, and which patches this one obsoletes, if any. Some patches may be aimed at fixing one particular problem and contain a very small number of files, while others( known as "jumbo patches") may fix a whole suite of programs or functionality. Common examples of these are the kernel and printing jumbo patches, both of which are frequently updated and tend to have high revision numbers. Recommended Patches Recommended patches are those that Sun suggests should be loaded onto the system, either at build time or as soon as possible after, even if you are not currently seeing any issues. These patches have been tested to work in conjunction with each other and will not cause any problems with the operating system. They are available from a number of locations, such as the Sunsolve CD-ROM, which is distributed to customers who have a maintenance contract, and Sun's Web site (sunsolve.sun.com, sunsolve.sun.co.uk, and other mirror sites). Sun's recommended patches are grouped by Solaris version number and can be installed by using the patchinstall script supplied on the Sunsolve CD-ROM, or the install_cluster command provided with the downloadable cluster, as described later in this chapter. Kernel Patches These are patches that affect the main running kernelUNIX itself. It is useful to note that we can also determine the version of the kernel jumbo patch that is installed by running uname. This will display the system type along with the kernel revision and will produce output similar to that shown below: hydrogen# uname -a SunOS hydrogen 5.6 Generic_105181-03 sun4u sparc SUNW,Ultra-5_10 hydrogen# From this we know that the kernel jumbo patch on our system is patch number 105181, revision 3. Security Patches Sun investigates any issues that may allow users to gain unlawful access to the system. If any problems are seen, they are fixed and the patch is released as a "security patch." It will depend on the use of the system as to whether all or none of the security patches will be installed. This will have to be determined by the system administrator. Public Patches Public patches are provided by Sun to allow noncontract customers to gain access to the important recommended and security patches. They are located on the Sunsolve Web sites and can be downloaded as required. Maintenance Updates These are a group of patches designed to upgrade the whole of Solaris to a new defined patch level. They are easier and faster to install than individual patches. | 
