In addition to all the Command Line and Server Config settings available in vanilla Terraria, tModLoader adds a few which are listed below.

TOBEADDEDLIST

1. -loadlib
2. -publish, -ciprep, -publishedmodfiles, -uploadfolder
3. -experimental
4. XNA-FNA Args like /gldevice:OpenGL
5. -steamworkshopfolder

savedirectory [pathToSaveDirectoryFolder]

Server and Client Command Line Argument
Specifies the save directory. The save directory will usually be %UserProfile%\Documents\My Games\Terraria\tModLoader​ on Windows, /Users/account/Library/Application Support/Terraria/tModLoader on Mac, and ~/.local/share/Terraria/tModLoader OR $XDG_DATA_HOME/Terraria/tModLoader on Linux. The directory /tModLoader will automatically be appended to the provided path. Use this argument to specify a different save directory. The save directory is the parent directory of the worlds directory and mods directory, so you can use only this parameter rather than both of those.

tmlsavedirectory [pathToSaveDirectoryFolder]

Server and Client Command Line Argument
Same as savedirectory above except /tModLoader won't automatically be appended to the provided path.

modpack [modpackname]

Server and Client Command Line Argument, Server Config.
Specifies a modpack to use by name. Omit the .json extension. The mods specified in the modpack (and only them) will be loaded. Useful for quickly launching a specified set of mods for people who might be doing multiple concurrent play-throughs with different sets of mods.

modpath [pathToModsFolder]

Server Command Line Argument, Server Config.
Specifies the folder to look for .tmod files. Useful for hosted servers as typically the default folder location is no accessable on dedicated hosts.

skipselect

Client Command Line Argument
Useful for modders who wish to quickly test their mod. This flag will automatically select the 1st player and world in the list, allowing the modder to launch directly into the game. Very useful when building and launching from Visual Studio.

If you wish to specify a specific player and world, you can use -skipselect "MyPlayer:MyWorld"

build [pathToModSource]

Server Client Command Line Argument
Builds the mod specified by the folder from source, useful for modders.

eac

Server Client Command Line Argument (Windows Only)
Enables Edit and Continue, useful for modders.

Usage

For dedicated server configs, follow the example shown in the serverconfig.txt file in the Terraria install directory. (for example, "modpath=/mymods/". Basically, [settingname]=[settingvalue])

Otherwise, use either a script (.bat on windows, .sh on linux/mac) to specify a command line argument. (for example "Terraria.exe -modpack friendsplaythrough") Windows users can also add parameters to shortcut files by adding to the end of "Target".

Examples

Windows Shortcut

Make a shortcut to the tModLoader exe file by either copy and then paste shortcut or by right click dragging the file to another place and selecting "create shortcuts here". Next, right click properties and edit the Target appropriately.

Launch Windows Client with a specific Mod Pack

See picture:

Dedicated Host

A Dedicated Host is a company that provides server hosting for a fee.

Edit the server config file that the dedicated host is using. Not every host is the same. You'll need to make sure that tModLoaderServer is being launched with either the command line argument or the server config line for the path to Mods folder. If you wish to use a Mods folder in the same folder as the tModLoaderServer executable, I believe you can use a relative path like "modpath=./Mods". You'll also need to set savedirectory since some mods store mod specific data in the save directory. (savedirectory is a command line only parameter.) Add -savedirectory ./ to the command that launches the server, which can be found usually on the website for your host.

Dedicated Hosts known to work

NodeCraft - Follow the instructions

GameServers - Add -savedirectory ./ to server command line

Akliz Hosting - Works as is.

Citadel Servers Hosting Company

AleForge

Dedicated Server (Self-Hosted)

If you have an extra computer around, you can use it to host a server 24/7 without paying for a Dedicated Host. Setting up a dedicated server involves installing the tModLoader files and configuring the computer to run the server forever (execute the tModLoaderServer script (Linux/Mac) or tModLoader.exe (Windows)).

Linux

If you'd like to install tModLoader on a Linux computer you have access to, but isn't the computer you intend to play on, below is a script that will setup tModLoader without needing Steam or Terraria installed. Make a linuxServerScript.sh file with the contents below in a folder where you wish to install the tModLoader server. chmod +x linuxServerScript.sh the file so you can execute it, then run it. This script downloads the latest tModLoader and does the extracting of the files for you. After installation, it is up to you to manage running the server whenever you want by running ./tModLoaderServer manually or with a script. You might want to use -config serverconfig.txt or the -tmlsavedirectory options to configure the behavior of the server as usual.

# Linux Server Install Script v1.1 by Chicken-Bones (some changes by jopojelly)
wget https://api.github.com/repos/tModLoader/tModLoader/releases/latest -O tMLlatest.json
tml=`sed -n 's/.*\(https.*Linux.*.tar.gz*\)".*/\1/p' tMLlatest.json`
wget $tml
tar xvzf tModLoader.Linux*.tar.gz
chmod a+x tModLoader tModLoader-* tModLoaderServer *.bin*
rm *.zip *.tar.gz *.jar tMLlatest.json

Visual Studio

Build/Edit/Test mods

Setting the Post Build event to "C:\Program Files (x86)\Steam\steamapps\common\Terraria\tModLoaderServer.exe" -build "$(ProjectDir)\" -eac "$(TargetPath)" will allow you to easily build and run your mod in Edit and Continue mode, facilitating efficient tweaking, modding, and testing. This is automatically added by default in all newly generated mods. Add -skipselect so you don't have to go through the menus for an even easier time. See Developing with Visual Studio for more information.