The server configuration requirements are:
A version of PHP supported by your Kickstart version. We recommend using a version of PHP which is currently supported by the PHP project for security reasons.
The PHP zlib extension installed and enabled. This should be enabled by default as it's required by Joomla and WordPress to install extensions / plugins.
Correct directory and file ownerships and permissions. Alternatively, you can create a world-writeable kicktemp directory and prove FTP or SFTP connection parameters (your server must have the PHP ftp, ssh2, or curl extension installed and enabled).
The last requirement must be further explained. PHP is bound by the file and directory ownership and permissions (Linux, macOS, …) or access control lists (Windows); these are collectively called permissions in the context of web software. In some rare cases, and mostly with self-hosting following outdated tutorials written using AI, the permissions will be such that PHP is not allowed to create folders or create, delete, and modify files on your site. In this case, you can work around this restriction by having Kickstart upload the extracted files into your site using FTP or SFTP. However, Kickstart still needs a temporary directory where it can extract each file before uploading it. This temporary directory is called kicktemp and must have permissions such that allow any user account on the server to write into it.
If you use the FTP, SFTP, or Hybrid mode, Kickstart will require the kicktemp temporary directory to be directly writable by PHP (usually, 0777 permissions help) or it will attempt to create a temporary directory of its own. If this procedure fails, Kickstart will notify you that the temporary directory is not writable.
Moreover, if you already have a site installed on the target server you have to ensure that all folders and files are writable. If not, Kickstart will fail and leave your site in a possibly broken state.