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Why the server start command cannot set a seed
The dedicated server’s documented world switch is -world, not -seed. Iron Gate Studio describes it this way: “-world “Dedicated” – A World with the name entered will be created. You may also choose an already existing World by entering its name.” The switch selects a world save by name; it does not provide a new procedural-generation seed.
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Adding an invented -seed argument to a stock launch script therefore does nothing useful. The reliable method is to generate the world in the normal Valheim client, where the world-creation screen accepts a seed, and then migrate that generated save to the dedicated server.
This distinction also explains why a server may appear to ignore a seed. If the name supplied to -world already identifies an existing save, the server loads that save. It does not regenerate the world with a different seed simply because you changed a command-line value.
What you need before migrating the world
- A Valheim client installation that can create a local world.
- The seed text you want to use and a final world name you can reproduce exactly.
- Access to the dedicated server’s files and launch script.
- The ability to stop the server completely before replacing or adding save files.
- A verified backup of both the local source world and the server’s current destination saves.
Choose a new world name when you are testing a new seed. Reusing a name that already exists on the server increases the chance that the old world will be loaded or overwritten. Do not delete an old save until the backup can be restored and has been checked.
How to put a custom-seeded world on the server
1. Create the world in the Valheim client
- Open Valheim and go to the world-creation screen.
- Choose to create a new world.
- Enter the desired seed in the seed field. Use the exact capitalization and characters you intend to preserve.
- Give the world a distinct name. This name becomes the save basename that the dedicated server will use later.
- Create and save the world, then exit the client after the initial world files have been written.
The seed is attached to the generated world data. It is not necessary, or supported by the documented dedicated-server workflow, to type the seed again in the server command.
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2. Stop the dedicated server and make backups
Use the server’s normal stop procedure and wait until the process has exited. Copy the complete local world save and the complete server-side save to separate backup locations. A backup made while the server is still writing can be incomplete, so do not copy files during an active save.
Keep the original server save untouched until the imported world has started successfully. If the destination already contains a world with the name you plan to use, either select a different name or move the old save aside only after confirming that your backup is usable.
3. Copy the complete world save set
Copy the full save set produced by the client, not a single file chosen by appearance. The documented migration pattern uses the matching .db and .fwl files. The .fwl metadata carries the seed in the implementation described by reloadlife, while the database contains the world state. Leaving out either half can produce a missing world, a failed load, or a world that does not represent the intended save.
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Valheim’s current save layout can also present a complete world directory rather than only two loose files. Preserve that complete directory layout when it is what your client or server uses. Do not rename extensions, edit the files, or combine files from different worlds.
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Iron Gate’s documented default locations are:
| Server platform | Default Valheim save root | What to check |
|---|---|---|
| Windows | %USERPROFILE%/AppData/LocalLow/IronGate/Valheim |
Use the account that runs the dedicated server, not necessarily the account used to play locally. |
| Linux | ~/.config/unity3d/IronGate/Valheim |
Use the home directory of the service account that launches the server. |
| Custom location | The directory supplied with -savedir |
Inspect the launch script; this override takes precedence over the default root. |
Place the imported save under the active root used by the server process. A file copied to a convenient-looking directory is invisible to the server if the launch script points somewhere else with -savedir.
5. Set the exact world name in the launch script
Set -world to the save basename, matching the name created in the client. Do not include .db or .fwl when the save consists of those files. For example:
-world "MySeededWorld"If the script contains other documented options, leave them in place and change only the world selection. A command may also contain separate values for the server’s browser name, password, port, save interval, backup behavior, and crossplay mode. Those settings do not replace the world name.
The three commonly confused identity-related switches have different jobs:
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| Option | Purpose | What it does not do |
|---|---|---|
-name |
Sets the name shown for the server in the browser. | It does not select the world save. |
-world |
Selects or creates the world whose save name matches the value. | It does not accept a procedural seed value. |
-password |
Sets the server connection password. | It does not identify or regenerate a world. |
6. Start the server and verify the connection
Launch the server with the updated script and watch its log rather than assuming that a running process loaded the intended files. Iron Gate’s guide identifies Game server connected. as the successful connection state. Wait for that message, then connect and inspect the terrain or other landmarks that confirm you are in the imported world.
If the server starts but presents a new-looking world, stop it before making further changes. Check the name, save root, and file pair first; repeatedly restarting with uncertain files can make diagnosis harder.
How world names and existing saves affect seeding
A seed is used when the world is generated. Once that world has been saved, the server’s job is to load the existing world data selected by -world. Changing a seed conceptually while retaining the same save name does not reseed the map.
Use this naming rule when managing several maps:
- Use a unique world name for each seed you want to test or host.
- Keep the name in
-worldidentical to the save basename, including spaces and capitalization. - Store backups with the world name and a date so that source and destination copies cannot be confused.
- Retain the old world under a separate backup name rather than deleting it immediately.
If a world with the requested name already exists, the existing save takes precedence. To create a different seed, choose a new name or remove the old save only after a verified backup and a deliberate decision to replace it.
Troubleshooting a server that ignored the custom seed
The script contains -seed, but nothing changes
Remove the unsupported argument and follow the client-creation and save-migration workflow. The stock dedicated server has no documented seed flag. A command-line value that the server does not recognize cannot alter the world metadata.
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The server loads the old map
- Stop the server completely.
- Read the value after
-worldin the actual script being executed. - Confirm that the corresponding save exists under the active root, including the directory selected by
-savedir. - Check whether an older save with the same basename is still present.
- Use a new world name for the imported map if there is any doubt about which copy should win.
The world does not appear in the server
Check that both matching .db and .fwl files were copied, or that the complete current world directory was preserved. Confirm that the files belong to the same client-created world and are located beneath the server’s active save root. A partial pair, a mismatched pair, or a copy made to the wrong root prevents the server from selecting the intended save.
The server starts but players cannot connect
First establish whether the problem is world loading or networking. The log should reach Game server connected.. If it does not, review the launch script and save path before changing world files. If it does, the world-selection step has completed and connection settings can be investigated separately.
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A replacement damaged the previous world
Stop the server, restore the verified destination backup, and start it with the original world name. Keep the imported save in a separate directory until it has been tested. Never use an unverified backup as the only copy of a live world.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Save intervals, backups, and crossplay settings
Seeding and migration do not require changing the server’s routine maintenance settings, but they matter once the imported world is live. Iron Gate documents -saveinterval 1800 as the default save interval: 1,800 seconds, or 30 minutes. Treat that figure as the documented default, not a guarantee that every hosting panel uses the same value.
The official server options also include automatic-backup arguments. Configure them according to the server’s documentation and retain off-server copies for important worlds. Automatic backups reduce recovery time, but they do not replace a deliberate pre-migration backup.
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The -crossplay option uses the PlayFab backend for cross-platform connectivity. It changes how players connect; it does not change the world seed or the files selected by -world.
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The file workflow is the same in principle, but operational control differs by environment.
| Approach | Control | Operational effort | Main risk |
|---|---|---|---|
| Self-hosted Windows or Linux server | Direct control over the launch script, save root, backups, and world names. | You must stop the process, copy files, set -savedir when needed, and maintain backups yourself. |
A script can point at the wrong root or an existing save can take precedence. |
| Managed Valheim server hosting | The provider may expose world upload and naming controls through a panel or file manager. | File placement can be simpler, but you must learn the panel’s active save path and restart procedure. | An upload may target a staging area, or the panel may retain an old world under the same name. |
For a managed service, ask where the active world directory is, how to stop the process safely, and whether the panel supports downloading a complete backup. The provider’s interface may hide the underlying -savedir setting, but the server still needs the complete save and the correct world name.
Pre-launch checklist
- The world was created in the Valheim client with the intended seed.
- The local world and current server world were backed up before copying.
- The complete save set was copied: matching
.dband.fwlfiles or the complete current world directory. - The files are under the active save root, including any path specified by
-savedir. -worldmatches the save basename exactly.- No unsupported
-seedargument is being relied upon. -name,-world, and-passwordhave not been confused.- The server log reaches
Game server connected.after startup. - A new world name is used when a different seed is intended.
The practical rule to remember
Generate the map where Valheim exposes the seed—the client—then move the finished world to the server. The server selects that imported map by its exact save name and active directory; it does not reseed an existing world through a documented startup switch.
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