> ## Documentation Index
> Fetch the complete documentation index at: https://docs.gcore.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Troubleshoot errors with ISO image installation

ISO images can be connected to a virtual server in VMmanager 6 either from a local file or via a direct URL. Connection failures are usually caused by a file format issue, a size limit violation, or an inaccessible URL.

## Local ISO upload fails

If the ISO image upload from a local file fails, check the following:

* The file extension must be lowercase: `.iso`, not `.ISO`.
* The filename must contain only letters and numbers.
* The file size must not exceed 8 GB.
* No more than three ISO images are allowed per account.

## Image URL connection fails

If connecting an ISO image via URL fails, check the following:

* The URL must be a direct link to the ISO file, accessible over HTTP or HTTPS.
* The server hosting the file must allow external downloads.

If the error persists, [contact support](/hosting/contact-our-technical-support).