postinstall

Postinstall refers to actions or scripts that are run after a software package has been installed. It is used to complete setup that the installer cannot perform, such as configuring system components, generating configuration files, or initialising data. Postinstall steps are typically defined within the package's manifest or included as separate script files and are executed by the package manager or installer at the end of the installation process.

Common environments include package managers and installers that provide post-install hooks. In Node.js projects, a postinstall script can be declared in package.json under the scripts field and runs after npm install. Debian and derivative distributions use a postinst maintainer script, which is executed after a package is installed, updated, or removed to adjust system settings. Other packaging systems may provide post-install hooks or a similar phase to perform tasks.

Typical tasks performed during postinstall include creating directories and files, setting permissions, creating or updating configuration, applying initial configuration data, downloading or generating assets, applying database migrations, updating caches, and running basic health checks. The exact actions depend on the software and its environment, and some tasks may require dependencies that are only available after installation.

Considerations for postinstall include ensuring robustness and idempotence where possible, avoiding user interaction, and minimizing potential disruption if the script fails. They can pose security and reliability risks if they execute untrusted code or rely on external resources during installation. Documentation, signing and verifying packages, and designing postinstall steps to fail gracefully or be easily skippable can help mitigate these risks.