Managing Configuration Files

Managing Configuration Files

Sometimes a distribution contains configuration files, which are either required or recommended for operation, that exist on the target in a modified form (an /etc/rpc file, for example). When the target system contains modified configuration files, Inst preserves the modified files during the installation in one of two ways:

If the new configuration file is required for operation, Inst copies the existing target version to a file of the same name, appending a .O (obsolete) extension to it (/etc/rpc.O, for example). Then it installs the new, required version of the file by its standard name (/etc/rpc).
If the new configuration file is recommended (but not required), Inst leaves the existing file on the target untouched; it writes the recommended version to a file of the same name, appending a .N (new) extension to it. You can use .N files at your discretion.
For example, assume that the target contains a modified /etc/fstab file before an installation and the distribution contains a new, recommended /etc/fstab. After the installation, the original target version is still in /etc/fstab; the new version is contained in /etc/fstab.N.

Note: In most cases, Inst handles modified configuration files with predictable results: after installation, the target contains an installed version and an alternate version of the file (which should subsequently be merged with the installed version and removed). However, if you repeat an installation of the same software, the results may be different.
For example, it is possible to create both a .O and a .N version of the same configuration file. This happens when Inst creates a .O version of the file and you modify the newly installed version instead of merging and removing the .O version. During the repeat installation, Inst compares the installed file with the version on the distribution; when it finds that the two are different, it creates a copy of the distribution version, assigning it an .N extension.

As another example, assume that the .N version of a configuration file is merged with the installed version and erased. During the repeat installation, Inst detects differences between the installed file and the distribution version, so it creates a copy of the distribution version, assigning it a .N extension.

The Configuration File Notice
Merging Configuration Files