# Customize Second-Generation Managed Package Installs and Uninstalls Using Scripts

Customize a second-generation managed package (managed 2GP) install or upgrade by specifying an Apex post install script to run automatically after a subscriber installs or upgrades a managed 2GP package. You can also specify an Apex uninstall script to run automatically when a subscriber uninstalls a managed 2GP package.

For more information, see [Run Apex on Package Install/Upgrade](https://developer.salesforce.com/docs/atlas.en-us.pkg2\_dev.meta/pkg2\_dev/apex_post_install_script.htm) and [Run Apex on Package Uninstall](https://developer.salesforce.com/docs/atlas.en-us.pkg1\_dev.meta/pkg1\_dev/apex_uninstall_script.htm).

Specify post install and uninstall scripts in the `sfdx-project.json` file.

```nolang
   "packageDirectories": [
      {
         "path": "expenser-schema",
         "default": true,
         "package": "Expense Schema",
         "versionName": ""ver 0.3.2"",
         "versionNumber": "0.3.2.NEXT",
         "postInstallScript": "PostInstallScript",
         "uninstallScript": "UninstallScript",
         "postInstallUrl": "https://expenser.com/post-install-instructions.html",
         "releaseNotesUrl": "https://expenser.com/winter-2020-release-notes.html"
        },
        ],
       {
         "namespace": "db_exp_manager",
         "sfdcLoginUrl": "https://login.salesforce.com",
         "sourceApiVersion": "47.0",
         "packageAliases": {
             "Expenser Schema": "0HoB00000004CzHKAU",
             "Expenser Schema@0.1.0-1": "04tB0000000719qIAA"
          }

```

You can also use the `--post-install-script` and the `--uninstall-script` Salesforce CLI parameters with the `sf package version create` command. The CLI parameters override the scripts specified in the `sfdx-project.json file`.

:::note
Include the Apex classes for your post-install and uninstall scripts with the metadata in your package.
:::

You can designate an active Dev Hub org user to receive email notifications for Apex gacks, and install, upgrade, or uninstall failures associated with your packages. In Salesforce CLI run `sf package create --error-notification-username me@devhub.org` or `sf package update --error-notification-username me@devhub.org`. In Tooling API, use the PackageErrorUsername field on the Package2 object.