Ubuntu 16.04.02 Hang on Reboot or Shutdown

Had a problem after an update that when I force a restart or a shutdown on my server, it hangs on the last part of the process.

To fix my problem, I had to edit the /etc/default/grub config file and added acpi=force apm=power_off to the config line, between the double quotation marks…

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GRUB_CMDLINE_LINUX_DEFAULT=""

and

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GRUB_CMDLINE_LINUX=""

do a update-grub after saving then reboot one more time.. ( force sa restart when it hangs )
After the restart, try another reboot, it should work now without hanging.

Source of the fix is from Here

Heap Dump and Remote Tomcat 8-OpenJDK 8 Memory Monitoring

Memory problem.. the thorn of web apps… I have to connect to my remote server to monitor its memory usage and produce a heap dump.
Bellow is the steps I had to configure the server to allow me to connect a remote monitor tool.

Requirement: VisualVM app, download here

  1. Access your catalina.sh file.
  2. Look for JAVA_OPTS, if none found, you can add your own.
  3. Add …
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    -XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=/path/to/heap/dump/folder/

    to the line if found, if not, you can do

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    JAVA_OPTS="JAVA_OPTS -XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=/path/to/heap/dump/folder/"

    The above code will force a heamp dump when the server encounter a out-of-mem exception.

  4. Next, to enable remote memory monitoring, add these commands after the line above, within the quotation mark, add proper spacing after each command…
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    -Dcom.sun.management.jmxremote.port=<port_num>
    -Dcom.sun.management.jmxremote.ssl=false
    -Dcom.sun.management.jmxremote.authenticate=false
    -Djava.rmi.server.hostname=<host_ip_add>
  5. Now, run VisualVM and create a new JMX remote connection, under the CONNECTION field, add host_ip_address:port_num
    ex. 111.111.1.1:5555

Congrats! You should now be able to connect to your server and monitor your memory usage!