It's Not Working

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This page consolidates all of the most common issues where the web-ui or a related function just doesn't work.

First things first! Did you remember to Update the Webui?

Also, do you see any traceback errors in the logfile /var/log/mineos.log?

Contents

Server Doesn't Start

Sometimes after hitting 'Start', the web-ui reports the command executed successfully with a green pop-up, but the server itself never starts. There's a lot of technical background to why this is not reporting a problem (red pop-up) relating to the use of screen. In short, when starting a server, the pop-up message reflects the return code of screen, but is denied the return/exit code of the relevant child-process, java.

Most frequently, the issue is because the host cannot allocate the requested heapsize (xmx value). To see the error hidden by the screen mechanism, log into SSH as mc.

mc@core ~$ cd /var/games/minecraft/servers/a
mc@core servers/a$ /usr/games/minecraft/mineos_console.py --this command_debug
'/usr/bin/java -server -Xmx10000M -Xms10000M -jar /var/games/minecraft/servers/a/minecraft_server.1.7.2.jar '
mc@core servers/a$ /usr/bin/java -server -Xmx10000M -Xms10000M -jar /var/games/minecraft/servers/a/minecraft_server.1.7.2.jar

Xmx > Available RAM

Error occurred during initialization of VM
Could not reserve enough space for object heap
Error: Could not create the Java Virtual Machine.
Error: A fatal exception has occurred. Program will exit.

Your Xmx value is greater than the available RAM. Reduce the amount dedicated or free up available memory by running fewer servers.

Xmx exceeds architecture limits

Error occurred during initialization of VM
The size of the object heap + VM data exceeds the maximum representable size

Your Xmx value exceeds what your system can understand in terms of the 32/36/64 bit architecture.

Xmx exceeds per-thread limits

Invalid maximum heap size: -Xmx10000M
The specified size exceeds the maximum representable size.
Error: Could not create the Java Virtual Machine.
Error: A fatal exception has occurred. Program will exit.

Your Xmx value exceeds what the OS can handle for a threadsize. This happens if you're using x86 and trying to allocate more than ~1500MB.

Bad java arguments

# /usr/bin/java -server something -Xmx256M -Xms256M -jar /var/games/minecraft/servers/myserver/minecraft_server.1.7.2.jar
Error: Could not find or load main class something

Your java_tweaks has an inappropriate value. Perhaps something should be -something?

rsync: change_dir

rsync: change_dir "/var/games/minecraft/profiles/vanilla174" failed: No such file or directory (2)↵rsync error: 
some files/attrs were not transferred (see previous errors) (code 23) at main.c(1070) [sender=3.0.9]

The /profiles/vanilla174 may vary, but the general idea is that the profile itself was not updated (and currently indicates an X, rather than a check box). Return to the profiles page and click update for the corresponding profile.

Permission Denied

mineos_console.py

# cd /usr/games/minecraft
# ./mineos_console.py
-bash: ./mineos_console.py: Permission denied

This error occurs because mineos_console.py lacks executable permissions. This step is part of the install instructions but may be undone by improperly resetting the scripts. Simply re-add "+x" to fix this:

SFTP

When trying to upload a file to the server, such as /var/games/minecraft/import, the file transfer is aborted, reporting Permission Denied. Just like how a normal user mc cannot move files into /etc because it is root-owned, the same principle prevents this action. You have a few options: logging into SFTP as root or to upload to an mc-owned directory and use elevated privileges to move it elsewhere.

By Linux convention for security, logging into SSH/SFTP as root is disabled. This can be modified by allowing root login, though this is not the preferred approach.

The recommended practice is logging in with an unprivileged user (such as mc), upload your file to the home directory (e.g., /home/mc), then via SSH, copy/move the file with sudo or by elevating to root with su -.

Webui buttons do nothing

In the webui, a yellow div pops up and states Server did not respond to request. This means your web session is outdated; this occurs if you keep the web-ui open and the mineos service restarts, such as by updating the Python scripts via git.

Server reports DENY -1/20

Deny is a MineOS-created convention to indicate that the server jar being used is not responding to Minecraft pings() in a recognized way. The most likely cause is you are using a plugin that significantly changes how the MOTD is returned to the client (motd is part of the mc ping protocol).
In cases like this, some plugins, in order to allow colorization or non-ascii characters, uses a non-standard delimeter that is not coded into the MineOS scripts. If this is the case, please report what server jar/pack (preferably the URL) you are using and try to provide a copy of your server.properties to me to test.

WebUI refresh takes very long

The most common cause for long delays in the webui is unrecognized responses to minecraft pings. If you are experiencing these delays, send me the results of the following commands in SSH:

root@core ~# cd /usr/games/minecraft/
root@core games/minecraft# ./mineos_console.py -d /var/games/minecraft ping_debug
a: current (1.7) - 1.7.4
bukrek: legacy (1.6) - 1.6.4-R2.0
ffff: forgemod (1.5) - 1.5.2-R1.1-SNAPSHOT
forge15: forgemod (1.5) - 1.5.2-R1.1-SNAPSHOT
forge16: forgemod (1.6) - 1.6.4-R2.1-SNAPSHOT
fsdfdfafsd: legacy (0.0) - dev-SNAPSHOT
old: legacy (1.6) - 1.6.4
unl: forgemod (0.0) - unknown

Your results will vary--greatly--but will show the same format: SERVER: SERVER_TYPE (GUESSED VERSION) - REPORTED VERSION