Linux-VServer

VServer is an open source project, the Linux virtual servers implemented on the basis of operating system virtualization for the Linux kernel. The product is open-source software that is released under the GNU General Public License ( GPL). It thus follows a roughly similar approach as OpenVZ.

The project was begun by Jacques Gélinas and is now cared for by the Austrian Herbert Pötzl. The product has nothing to do with the Linux Virtual Server, which should ensure a uniform network load ( load balancing).

Linux - VServer provides the possibility of parts of a computer system such as the file system, processor time, network addresses, and divide the main memory so safe and secure demarcation between that individual processes have no way out of their partition of their agreed work area to access.

Each partition or each work area represents a so-called security context in which the virtualized computer system forms a virtual server. One of the chroot mechanism similar tool provides access to these security context. The boot this virtual server is then restricted to performing an init in that security context, the shutdown corresponds comparable to a termination of the proceeding in that security context processes. The Security Contexts, so the virtual machines that are powerful enough to use unmodified example, many Linux distributions and can be processed, including Debian and Fedora.

Virtual servers are typically used by Web hosting service providers, as they allow simultaneous summary of the computer's resources, a clean separation of different virtual machines, and customer foreclosure of these machines with each other. To comment on such installations with as little disk space, the file system for each virtual server is set up as a copy- on-write hard link to a virtual file system. This hard link has special file system attributes, replace with a detected change the file to be written by a written safe and transparent real copy of the file.

Linux - VServer exists in two different versions, a stable version and a developer version V.2.2.x V.2.3.x for the 2.6 Linux kernel, as well as a stable version for the Linux kernel 2.4.

Comparable virtualization mechanisms

Other comparable virtualization techniques are OpenVZ, of the FreeBSD Jail procedures, Solaris Containers and FreeVPS (an early lead ( Fork ) of Linux - VServer ).

Benefits

• Virtual servers use the same system call interface and do not generate additional load through emulation.
• The virtual server must not be secured by a non-transparent disk image, but can use a common, shared file system ( by copy- on-write hard links ). This makes the backup of a virtual server easier and allows you to use the available disk space for multiple virtual servers.
• Processes within the virtual servers run as normal processes on a computer system. This is far more efficient in terms of memory usage and I / O load than the complete emulation of a computer, the unused main memory or disk space can no longer ask the host or other virtual servers.
• Processes within a virtual server are processed by the scheduler of the host computer, allowing concurrent execution on multiprocessor (SMP) systems for the host processes the virtual server. Such an implementation for complete emulation of a computer would be expensive.
• The network connections are realized by packet separation takes through virtualization; also an additional packet processing is avoided.

Disadvantages

• Linux - VServer on the host requires a modified operating system kernel.
• All virtual server use this same kernel and are therefore also susceptible contained therein bugs and security vulnerabilities.
• There are neither clustering nor adoption process possible; the kernel of the host computer and the host computer itself still form a single point of failure for all virtual servers.
• Since the network connections based on a separation package and not on a virtualization, none of the virtual server can build up their own internal routing tables or used as a firewall machine.
• Some of the most hardware-specific system calls such as the real time clock and proc parts of the / and / sys file system are not virtualized.
• Linux - VServer does not yet allow assignment of I / O bandwidth to each virtual server. This option is available only in the development versions, but not in the stable version.