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Release Management/User Mode Linux


Intoduction to UML(User Mode Linux)

User-mode Linux (UML) enables multiple virtual Linux systems (known as guests) to run as an application within a normal Linux system (known as the host). As each guest is just a normal application running as a process, this approach provides the user with a way of running multiple virtual Linux machines on a single piece of hardware, offering excellent security and safety without affecting the host environment's configuration or stability.

To explain UML better I would say, it is technically a Virtual OS rather than a Virtual System.




As per installation is concerned UML requires only one package to be installed, that is uml-utilities.


Debian users can install it using

apt-get install uml-utilities


Gentoo users can install it using

emerge -av sys-apps/usermode-utilities



Configuring UML consists of steps like downloading Kernel (script) and filesystem (block device).

For normal functionality of UML user has just download the required files and follow these simple steps

bunzip2 kernel.bz2 filesystem.bz2
chmod 755 ./kernel
./kernel ubd0=filesystem mem=1024M tuntap=,,,

The Twist

But @Openbravo while configuring UML we made some changes. To explain the changes I would first like to explain the structure UML. It boots from a script that acts a kernel for the virtual environment in the process of booting it looks for a block device which contains a minimal/full Operating System. On understanding this behavior of UML we changed the block device with our own Xen image (as this is also a block device). The purpose of replacing the image was to get a pre-installed Openbravo instance in our virtual system.


User-Mode Linux is a safe, secure way of running Linux versions and Linux processes. Run buggy software, experiment with new Linux kernels or distributions, and poke around in the internals of Linux, all without risking your main Linux setup.


Their are a number of pros related to UML.


As such I don't see any cons in UML, but after having The Twist we fased some issues, like

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