In order to put a JVM in a RAM disk we are going to use the tool SquashFS.
Use the following command to install the Squash FS tools.
sudo apt-get update sudo apt-get install squashfs-tools |
Make a squashfs file out of your desired JVM:
cd /usr/lib/jvm sudo mkdir ramdisk mksquashfs /usr/lib/jvm/java-8-oracle /usr/lib/jvm/ramdisk/java-1.8.0.91-oracle.sqsh |
At this point you have an existing JVM squashed in .sqsh file with a roughly size of 176M:
user@machine:/media$ ls --block-size=M -al /usr/lib/jvm/ramdisk/java-1.8.0.91-oracle.sqsh -rw-r--r-- 1 user users 176M May 12 15:53 /usr/lib/jvm/ramdisk/java-1.8.0.91-oracle.sqsh |
Create a mountpoint for the ramdisk:
sudo mkdir /media/ramdisk-java-8-oracle |
Edit your /etc/fstab and define your mount point as a tmpfs by adding the following declarations:
# change the default size for the ramdisk tmpfs /media/ramdisk-java-8-oracle tmpfs defaults,size=350M,mode=1777 0 0 /usr/lib/jvm/ramdisk/java-1.8.0.91-oracle.sqsh /media/ramdisk-java-8-oracle squashfs ro,defaults,loop 0 0 |
If you reboot at this point you will have a ramdisk of 350M defined at /media/ramdisk-java-8-oracle filled with your squashed JVM:
user@machine:/media$ du -hs ramdisk-java-8-oracle/ 349M ramdisk-java-8-oracle/ |
That way we know how correctly size what we need for our ramdisk.
350M for a java-1.8.0.91 from Oracle.