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Launch arguments and command-line switches

Some Rust server options are not console variables at all. They are command-line switches, read from the line that starts the server, and no amount of editing server.cfg will turn one on. The Launch arguments editor is where those go, and it is also where you can see the exact command line Crucible Local Server uses for that server.

It lives at the bottom of the Config tab, under Launch arguments (advanced), next to the server.cfg editor. Every server has its own, so one server can run a switch while the others do not.

Switches are not convars

Section titled “Switches are not convars”

The difference is worth two sentences, because it is the whole reason this editor exists.

  • A line in server.cfg is a console command the game runs while it boots. It can set any convar, and nothing else.
  • The command line can do both. +some.convar value sets a convar before the cfg is read, and -someswitch sets a flag that is not a convar and has no cfg equivalent.

-useNewNavmesh is the second kind. Rust reads it straight off the process command line, and its own console tells you so: run one of the rustnav commands without it and the server replies “Restart the server with command line argument -useNewNavmesh”.

Add an argument

Section titled “Add an argument”
  1. Select the server, switch to Advanced, and open the Config tab.
  2. Expand Launch arguments (advanced).
  3. Type your argument on its own line below the divider, one argument per line.
  4. Press Save, or Ctrl+S.

A switch is just its name, like -useNewNavmesh. A convar takes a value after it, like +ai.move false. If a value contains a space, wrap it in double quotes.

Arguments apply the next time the server starts. Saving while a server is running does not change the server that is already up, so restart it when you are ready.

What the top half is

Section titled “What the top half is”

Everything above the divider is built by the app from this server’s settings, and it is rebuilt on every start. That is the server identity, the game and query ports, the RCON port and password, the game mode, the map URL for a custom map, and the log file the in-app console reads.

You can read it, which is the point of showing it, but you change it in the settings above rather than here. Editing one of those lines is refused when you save, and the message names the field to change instead, for example the Game port.

Anything you add below the divider is yours. It is kept exactly as you typed it, comments included, and it is passed to Rust after the managed arguments.

When it tells you something is wrong

Section titled “When it tells you something is wrong”

The editor checks every line as you type. Problems appear under it, with the line number, and the Save button stays disabled until the errors are gone.

It stops the save for:

  • An unbalanced quote.
  • A line that is not an argument, meaning it does not start with - or +.
  • A convar with no value, like +ai.move on its own.
  • Two arguments on one line. Put each on its own line, or quote it if it is part of the value.
  • The same argument twice.
  • A line that fights a managed argument, which names the setting to change instead.

It also shows a warning that does not block the save: a convar you set here that server.cfg also sets. The command line wins, so the cfg line is ignored, and knowing that saves an afternoon of wondering why a setting in the form does nothing.

Removing them again

Section titled “Removing them again”

Remove custom arguments clears everything you added and leaves the managed command line alone. The button is greyed out when a server has no custom arguments of its own.

Coming from a .bat file

Section titled “Coming from a .bat file”

If you have run a Rust server by hand before, you had two things: a .bat file full of arguments, and a server.cfg full of convars. Crucible Local Server has both, in the same two shapes. This editor is the .bat line, and the server.cfg editor right above it is the file. The difference is that the app writes the parts it manages for you, so a port change stays a port change instead of an edit in two places that can disagree.

Section titled “Related”