Encap 2.0: Package Scripts

Script	Description
preinstall	Executed before installation.
postinstall	Executed after installation.
preremove	Executed before removal.
postremove	Executed after removal.

If a preprocessing script returns a non-zero exit code, the package manager must immediately abort processing the package. A postprocessing script will only be executed if at least one link has been successfully created or removed, as appropriate, during the processing of the package.

Package scripts must adhere to the following guidelines:

1. A package's scripts may not modify system configuration files that cause it to be run when the system reboots (such as /etc/inetd.conf or any rc script) unless it has installed all data files that it needs to start properly. This is necessary to prevent the system from being unusable after a reboot.
2. A package script which modifies or replaces pre-existing files must always save a copy with the suffix .pre.pkgspec, where pkgspec is the pkgspec of the package being installed.
3. A package script which installs configuration files outside of the Encap tree must copy the files to that location, rather than create symlinks into the Encap tree. This prevents problems which can be arise when the Encap tree is unavailable at boot.
4. A package script which installs configuration files outside of the Encap tree must not replace pre-existing customized versions, except where necessary to adhere to the previous guidelines. An example of a valid exception is when a package is upgraded to a version which changes the configuration syntax.
5. A package script must react properly when it is invoked multiple times. For example, if a postinstall script intends to add an entry to /etc/services, it must not do so if the entry already exists.
6. Package scripts may not prompt the user for input. A package script's stdout and stdin may be redirected somewhere other than the terminal. However, a script's stderr must always be sent to the terminal so that the user is informed of error conditions.