# The mod loader's installer stopped with an error

The installer of Forge, NeoForge or Quilt that the startup script runs exited with an error code, so the loader was not installed and the server could not start.

- Code: `installer_failed`
- Severity: fatal
- Category: Startup
- Server types: Forge, NeoForge, Quilt
- Page: https://failures.perland.online/failures/installer_failed/

## Example log

```text
[mc-image-helper] 16:21:09.902 ERROR : 'install-forge' command failed. Version is 1.74.0
me.itzg.helpers.errors.GenericException: Forge installer failed with exit code 1
```

## Parameters

| Parameter | Meaning |
| --- | --- |
| `installer` | The installer that failed, in lower case as the error names it, such as forge or quilt. |
| `exitCode` | The exit code the installer ended with. |
| `command` | The startup helper's command that ran the installer, such as install-forge or install-quilt, when its error line was read. |

## Log lines this page covers

- `'install-forge' command failed. Version is`
- `GenericException: Forge installer failed with exit code`
- `GenericException: Quilt installer failed with exit code`

## What it means

A modded server needs its mod loader installed before the game can run. The server's Docker image downloads the loader's official installer and runs it at the first start, or after the version changes. Here the installer ran but ended with an error, so the loader was not installed and the server stopped.

The issue names the installer and its exit code. When the installer said before failing that it needs a newer Java, that is shown instead as `installer_java_mismatch`, and this line is left out as the same failure.

## Why it happens

- **The installer could not download its libraries.** It fetches the game and its libraries from Mojang and the loader's own servers, and a failed connection ends it.
- **A Minecraft and loader version pair the installer does not support.**
- **The disk is full** or the data folder cannot be written.
- **A half-finished earlier installation** left files the installer trips on.

## How to fix

1. Start the server again: a download that failed inside the installer often works the next time.
2. Read the lines just above the error. The installer usually prints the step that failed, such as a library it could not download.
3. Check that the Minecraft version and the loader version go together on the loader's own download page.
4. Check that the host has free disk space.
5. If an earlier installation was cut short, make a backup of the data folder, then remove the loader's files (the `libraries` folder and the loader's server jar or launch script) so the next start installs it cleanly. Never remove the world.

## In Perland

The issue appears in the server's Diagnosis tab with the installer and its exit code. The Minecraft version and the loader version are set in the server's Settings; a server made from a Git modpack takes them from the pack instead.

## References

- [Docker Minecraft Server: server types](https://docker-minecraft-server.readthedocs.io/en/latest/types-and-platforms/)
- [Forge documentation](https://docs.minecraftforge.net/)
- [NeoForge documentation](https://docs.neoforged.net/)