LiquidVM Overview

LiquidVM is a single-process, single-user VirtualMachine designed to run Java processes efficiently on a virtual environment. Details about LiquidVM are provided in the following topics:

What is LiquidVM?

LiquidVM is a virtualization enabled version of the JRockit JVM that can run on a hypervisor without a standard OS, allowing Java applications to run directly on the virtualized hardware.

The LiquidVM Tools component in WLOC provides tools to create LVM-based instances that can run in a VMWare ESX environment, as well as the run-time components necessary to manage such LVM-based instances.

JRockit JVM as the Java runtime component.
A scaled-down OS kernel that replaces the OS for LiquidVM. It differs from a normal OS in that it is a single-user, single-process environment that is designed to only run a single JVM. No other processes can be started. It implements the following services that the JRockit JVM needs to run Java:

Low-level memory management
Thread-scheduling
File system
Networking
Interaction with the hypervisor

Java-based services, started after the JRockit JVM has started, that run in threads that are separate from your application. The LiquidVM services are:

LiquidVM SSH-service
LiquidVM heap-resizer
LiquidVM syslog publisher

Tools that are used to create and control LiquidVM instances. The LiquidVM tools run on a standard OS; they do not run inside LiquidVM. LiquidVM tools include:

LiquidVM launcher—used to start and stop LiquidVM instances
LiquidVM Configuration Wizard—used to configure the connection between LiquidVM and the VMware Virtual Center

A virtual local disk for each virtual machine. The local disk removes the dependence on NFS and provides faster and more secure file transfers.
The ISO Builder component allows you to create an ISO-9660 file from a template ISO-9660 file, typically a WLS-VE-based or LVM-based ISO file. The tool also allows you to add data files (e.g., application files) along with the content of the source template file in the resulting ISO-9660 file. For more information, see Using the WLOC ISO Builder.

Understanding the LiquidVM File System

The LiquidVM file system is very similar to most Unix-like OSes. There is a single root (/) directory; disks and remote NFS file-shares can be mounted in sub-directories. By default, the virtual disk, if configured, is mounted in the root directory (/).

Table 1-1 WLOC Directory Structure
Directory	Contents	Notes
`/appliance`	The contents of the LiquidVM ISO image	This directory is read-only. The LVM ISO image file to be used is specified in the `bea.lvm.info` file using the `vmwareDiskPath` parameter. For example: `vmwareDiskPath=[storage1] wloc/wloc10.iso`
`/bea`	`patch_weblogicnnn`	The default location for the BEA Home directory on the virtual local disk. You can change the location of the BEA Home directory by specifying the `-Dbea.home` option in the WLOC start script. The BEA Home directory contains any WLS patches.
`/domain`	server-root directory log files application classes	The default location of the WLS domain and the current working directory for WLOC.
/tmp		Directory for temporary files created when WLS boots. The temporary files are erased each time the LiquidVM instance reboots.

Using the Virtual Local Disk

LiquidVM provides a virtual local disk for each virtual machine. The local disk can be mapped to a SAN disk attached to the ESX server. You specify the size of the disk by passing the diskSize parameter as a startup option to the LiquidVM launcher. To do so, specify the disk size in the WLOC start script using the LVM_DISKSIZE option. The default is 1GB (1024). For more information, see Using the LiquidVM Launcher Commands.

The first time that you boot LiquidVM, it detects that a virtual hard disk is attached and that it is empty. LiquidVM formats the disk and mounts it in the root directory (/).

To the VMware ESXserver, the virtual hard disk is a vmdk file. The vmdk file is placed in the same directory as the Virtual Machine's configuration file on the ESX server/SAN. You can specify which VMware datastore the VM configuration files and the virtual hard disk should be placed in by specifying the vmwareVmDatastore option to the launcher. To do so, add a vmwareVmDatastore= entry to the bea.lvm.info file.

You can transfer files to and from the local disk by using the LiquidVM SSH service. For more information, see Using the LiquidVM SSH Service.

Determining the Amount of Free Disk Space

To determine the amount of free disk space on your virtual machine while the WLOC instance is running, press F1 in the VMware VM console. Details about the running system, including the amount of free disk space, are displayed in the console.

Increasing the Size of the Local Disk

If your disk is full, you can shut-down WLOC and specify a larger disk by increasing the value of the LVM_DISKSIZE property in the WLOC start script.

VMware does not provide a way to increase the size of the disk. Instead, when you restart WLOC, the LiquidVM launcher creates a new larger disk and copies the files from the old disk to the new disk. When you increase the size of the disk, the initial restart of WLOC will take longer depending on the size of the disk and the amount of files to be copied.

Using the LiquidVM SSH Service

LiquidVM provides a SSH2-compatible service for transporting files to and from LiquidVM. The SSH service does not provide shell services; that is, LiquidVM does not support scripts or editing files from the SSH shell.

The SSH service in LiquidVM provides an encrypted communication channel between the server and the client. The encryption protocol used is AES-128. Unencrypted communication is not supported.

You can transfer files using the scp and sftp extensions to SSH. The Linux OS includes sftp and scp clients. On Windows systems, several free SSH2 clients are available for download (e.g., PuTTy, WinSCP, FSecure, and FileZilla.)

You authenticate with the SSH service using either password-based or public/private key authentication. For more information, see Authenticating with the SSH Service.

LiquidVM is a single-process, single-user environment, therefore only the liquidvm user is supported. Multiple users cannot login into LiquidVM.

SSH Listen Port

The SSH2 server normally listens on the standard SSH port (port 22), but you can change the SSH listen port by setting the Java property -Dlvm.ssh.port. You may prefer to change the SSH port to something other than the default (port 22), since most SSH attacks try to attack the default port.

Authenticating with the SSH Service

When you use the LiquidVM launcher to create a new instance, you can specify the type of authentication to be used. To use public/private key authentication, you need to provide your public key as a startup option to the LiquidVM launcher. To do so, specify the location of the public key in the WLOC start script using the LVM_SSH_PUBLIC_KEY option. For more information, see Using the LiquidVM Launcher Commands. When you attempt to authenticate with the SSH service, you will be prompted to provide your private key.

In a development environment, you may not want to bother with keys and secure passwords. In that case, LiquidVM provides a simpler, but unsafe method, of specifying an SSH password in clear-text from the launcher. You can specify the password in the WLOC start script using the LVM_SSH_UNSAFE_PASSWORD option.

Installing a Real Password In Addition to a Public Key

If you should happen to lose your private key, it is good idea to have a secure real password as well, so that you can still log in and access the files on the local disk. You can do password-based authentication that is not clear-text, follows:

Using either the public/private-key authentication or the unsafe clear-text password, log into the virtual machine using SSH.
Type passwd. You will be asked for the existing password. If you are using a public key, leave it blank and press Enter.
When prompted for new password, enter a secure real password.
Confirm the new password.

This installs a real password; therefore, the unsecure clear-text password will no longer work. The public key authentication will continue to work if you prefer to use that method.

Auditing SSH Actions

The SSH service will send audit messages to the syslog for the following actions:

You can use remote logging facilities to send these message to a remote log-collector for compliancy verification.

Using LiquidVM in Passive Mode

To copy files to or from the LiquidVM instance before starting WLS, you can use LiquidVM in passive mode. In passive mode, only the LiquidVM services, including the SSH service, are started. WLS is not started.

To start LiquidVM in passive mode, add the startMode=passive option to the launcher start arguments. Once LiquidVM is started in passive mode, you can log in over SSH and transfer your files. When you have finished transferring your files, you can either restart the server or login over SSH and run the start command to resume execution.

If you want the LiquidVM launcher to wait for the SSH service to be started before the launcher exits, you can specify waitForSSH=true. This can be useful in a scripting environment where you first start the instance and then you want to copy files from or to the server as soon as SSH is running on the newly started server.

LiquidVM User Guide