Download mrpack-install through GitHub releases (or your distro's package if it has one) and take a look at the commands on the README. In Legacy4Server's case, to install in your server you would run:

mrpack-install Legacy4Server [optional version number]

It's a good idea to have some knowledge on using Docker before doing this.

1. Make sure you have Docker Engine installed properly according to the Docker docs
2. Create a new directory
3. Place the contents below in a file called docker-compose.yml. This Compose file also contains some other server tweaks meant for performance, such as disabling sync-chunk-writes, reducing render and simulation distance, and more
4. Run docker compose up -d in that directory

For any other information, you can read through the Docker Minecraft Server documentation.

services:
  mc:
    image: itzg/minecraft-server
    tty: true
    stdin_open: true
    ports:
      - "25565:25565"
    environment:
      EULA: "TRUE"
      # Adrenaline and other mods
      MOD_PLATFORM: MODRINTH
      MODRINTH_DOWNLOAD_DEPENDENCIES: required
      MODRINTH_MODPACK: legacy4server # this installs the latest version of Legacy4Server, you can also use a specific MR link to a version
      MODRINTH_PROJECTS: spark, chunky # comma separated list of extra mods
      # Server properties
      VIEW_DISTANCE: 8
      SIMULATION_DISTANCE: 5
      SYNC_CHUNK_WRITES: false # having this set to false will significantly improve performance but may cause desync issues and (extremely rare) data corruption. set to true if you don't have a backup system
    volumes:
      # Attach the relative directory 'data' to the container's /data path
      - ./data-blocked:/data

mcman is a tool for managing the mods/plugins/configurations of a Minecraft server. First, install mcman from releases. To import Legacy4Server while initializing a server, use this command:

mcman init --mrpack mr:legacy4server

After initializing and importing the mrpack, run mcman build to build the server into the server/ directory, from which you can call cd server && sh start.sh or cd server && call start.bat. For more information, check out mcman's docs.

See the mrpack4server Git repository for installation info. modpack-info.json:

{
	"project_id": "legacy4server",
	"version_id": "version id or name"
}