Linux server "Could not find the main class"

[PJUmbreon]

I'm working on setting up my private server to run Pixelmon and Tale of Kingdoms for me and my friend to play on it. However, when I try starting up the server with Forge only, I get this error:

[ec2-user@ip-10-252-138-154 MinecraftServer]$ sudo java -Xmx512M -Xms512M -jar minecraft_server.jar nogui
Exception in thread "main" java.lang.NoClassDefFoundError: aki
Caused by: java.lang.ClassNotFoundException: aki
        at java.net.URLClassLoader$1.run(URLClassLoader.java:217)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:321)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
Could not find the main class: net.minecraft.server.MinecraftServer. Program will exit.

Any way to fix this?