Valheim: Server not booting

Valheim servers are easily configurable, and therefore, also easily breakable. It is not uncommon for a mod, server configuration, or borked server files to be the reason why a server is stuck in booting mode. In this article, we will go through potential reasons why your server won't boot, and what you can do to fix it.

Outdated or incompatible mods

A common indicator that there is an underlying mod issue is the following server logs (found in the Console tab of the Valheim server control panel):

May 22 11:35:05:  Fallback handler could not load library /home/dathost/valheim_ds/valheim_server_Data/MonoBleedingEdge/x86_64/data-0x559640788710.so
May 22 11:35:05:  Fallback handler could not load library /home/dathost/valheim_ds/valheim_server_Data/MonoBleedingEdge/x86_64/data-0x55964078c030.so
May 22 11:35:05:  Fallback handler could not load library /home/dathost/valheim_ds/valheim_server_Data/MonoBleedingEdge/x86_64/data-0x559640782f10.so

Although these logs do not directly state any mod issues, if they are recurring consistently in the server console, it is almost always due to an underlying mod issue. Now, what specifically can be the reason for this?

Common reasons why mods won't work

• The mod(s) are outdated. When a large Valheim update is released, such as Hildir's quest or Ashlands, it is very common for mods to then become incompatible. Always ensure that you update your mods after a large game update, or remove the mods while waiting for an update.
• A certain combination of two or more mods won't work together. Sometimes, it is the case that two different mods simply cannot operate together. Keep that in mind when installing a large modpack.
• Some mods are server-specific. For instance, some mods will require you to add the server IP to the mod configuration, or to the mod-creators website. If you relocate the server after you have configured the mod, then the mod won't work since the server IP has changed. Remember to keep your mod configurations updated.
• The mod is not server-compatible. Although a mod will work on your local game, it doesn't mean that it will be in a server environment. Always ensure that the mod is server-compatible when downloading a mod.
  
  

How to troubleshoot a mod-related booting issue

Unfortunately, there is no time-efficient way of troubleshooting mod-related issues since the server logs will most often not expose the faulty mod. For that reason, we must check all mods in order to find out which one(s) is causing the booting issue.

Potential Quick Fix

There have been a few cases when removing all mods, and simply re-uploading them have solved the modding issues. Clarification:

1. Remove all mods from the server entirely.
2. Start up the server and wait until it is fully started.
3. Shut down the server.
4. Re-upload the mods to the server and wait until they are fully uploaded.
5. Try starting the server again.

If this didn't help, please try the method above instead.

The password cannot be the same, or contain, your world name

An often overlooked booting issue is when the server password is the same, or contains the world name. Always make sure that the password of the server is completely different to the world name.

How to update the server password