Making changes to /etc and /var

Because /etc and /var are symbolic links, and not directories, this difference affects how you install service and make updates when doing a system replace. Use the procedures in this topic if the installation process must create one or more directories, or you would like to copy files from one /etc or /var file system to another/etc or /var file system.

The /etc file system is the location for your own customization data for products. You set up the /etc files and you maintain their content. The /var file system is the location for IBM® product information, that is created, used, and maintained by IBM products.IBM products might create directories under /etc or /var during installation, but IBM does not create files under /etc or /var during SMP/E installation. Because IBM products do not create files into /etc or /var, there is no possibility that SMP/E installation of an IBM product or service will overlay your own files within /etc or /var.

Because /etc and /var are symbolic links, not directories, they cannot receive product or service code. If you are installing service or products that must write to /etc or /var, you need to change /etc or /var to a directory, install the code, and then change /etc or /var back to a symbolic link. The sample JCL for those tasks are in SYS1.SAMPLIB; they are:

Mount a clone of the system that you are installing into the /service mount point.
Run the sample job BPXISETD to convert the /service/etc and /service/var symbolic links to directories. Pass the /service parameter to the REXX exec.
Optionally, you can use BPXISJCL to submit the job in the background.
Mount the clone of the serviceETC.HFS of the system you need to service at /service/etc. For /var directory updates, mount the clone of serviceVAR.HFS of the system you need to service at /service/var.
Install the service, which might include running REXX execs that create directories under /service/etc or /service/var. At this point, you can copy /etc files from an existing file system's /etc to /service/etc, if you wanted to bring forward any configuration files, and change them properly.
Unmount the /etc after everything is installed from /service/etc. Unmount the /var after everything is installed from /service/var.
Run the sample job BPXISETS to convert the /etc and /var back to symbolic links at /service/etc and /service/var, respectively.

Example:

If you are mounting a maintenance file system named MAINT.ETC at a symbolic link (/service/etc) that points to the /SYSTEM/etc mount point where the active file system (PROD.ETC) is mounted, you must convert the symbolic link to a directory first.

Guideline: While you can mount on a symbolic link that points to a directory, you must make sure that the mount point that your symbolic link is pointing to is not still mounted on by the original /etc file system.

For information on how to migrate the /etc and /var file systems during a system replace, see z/OS® V2.1 Migration "Migrate /etc and /var system control files