Command blocks

A command block is a block that can execute Minecraft commands.

Usage

In order to use (open) a command block, the player must:

1. in server.properties enable enable-command-block by setting the value to true (the server must be restarted for the changes to take effect after editing the file)
2. have OP
3. be in gamemode creative

However, it is always better to use a plugin or mod instead of a command block, both in terms of server performance and security. Thus, if command blocks are enabled, it is most ideal to disable them by setting enable-command-block to false in the server.properties file located in server root directory.