Update: If you're using a more recent Feed the Beast mod pack (1.16.5 or later), you must run the "FTBInstall.bat" (Windows) or "FTBInstall.sh" (Linux) for it to download required library files. Sometimes these are named differently like "Install.bat". This will download the library files automatically, with no need to download these. This guide is only for older mod packs that generally are not supported and should not be used.
If you're setting up Forge mod loader onto your Minecraft server, you might run into the following error while trying to get your server to run.
You will need to add them to your server before FML and Forge will run successfully.java.lang.ClassNotFoundException: net.minecraft.launchwrapper.Launch[Server] INFO We appear to be missing one or more essential library files.
To fix this:
1.) Download the required libraries manually.
Get FMLLIBS Libraries
2.) Unzip the folder you downloaded then upload the contents to your servers "/libraries" folder, if the folder isn't there, create the folder first in your file manager/FTP.
Note: If you've uploaded your mod pack to a remote server with an FTP client like FileZilla, these "forge missing libraries" might be caused by the FTP client not uploading all of the library files. FileZilla sometimes leaves out important library files when uploading, so check the "Failed Uploads" queue.