This topic describes the mounting of the root file system.The root file system contains system code and binaries, including the /bin, /usr, /lib, /opt, and /samples directories. These directories contain files that are installed and serviced by SMP/E.

For systems with shared file system support, mounting the root file system read-only is optional. For more information about the version file system, which is also known as the root file system, see Sharing file systems in a sysplex.

Rule: In a sysplex, the /etc, /dev, /tmp, and /var directories must have their own file system, separate from the root file system. Having those files in their own file system is also good practice for non-sysplex systems.

To ensure the integrity of file systems, users must configure their systems to propagate SYSTEM ENQs on file systems. The serialization used by file system mount is a SYSTEMS ENQ on SYSZDSN and the data set name. If this ENQ is not properly maintained, the file system will be damaged. The SYSZDSN ENQ is held on the file system until the file is unmounted. A file system can be mounted read/write on a single system, or read on multiple systems. A file system that is mounted read/write cannot be shared by multiple systems. For more information about SYSZDSN, see the IBM® Redbooks® publication Hierarchical File System Usage Guide.