Linux VServer
| Linux VServer
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|---|---|
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| Basic data
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| developer | Herbert Pötzl (community project) |
| Current version |
0.30.215 ( March 17, 2008 ) |
| operating system | Linux 2.6 and 2.4 |
| programming language | C. |
| category | Virtualization |
| License | GPL 2 ( Free Software ) |
| Linux-VServer.org | |
VServer is an open source project that implements virtual Linux servers based on operating system virtualization for the Linux kernel . The product is free software released under the GNU General Public License (GPL). It follows a roughly comparable approach to OpenVZ .
The project was started by Jacques Gélinas and is now being supervised by the Austrian Herbert Pötzl. The product has nothing to do with the Linux Virtual Server , which is supposed to ensure even load balancing.
Linux-VServer enables parts of a computer system such as the file system , processor time , network addresses and main memory to be divided and securely separated from one another in such a way that individual processes have no way of accessing outside their partition, the work area they are allowed to use.
Each partition or each work area represents a so-called security context in which the virtualized computer system forms a virtual server . A tool comparable to the chroot mechanism provides access to this security context . The booting of this virtual server is then limited to performing an init in this security context ; the shutdown is comparable to terminating the processes running in this security context . The security contexts , i.e. the virtual machines, are powerful enough to be able to use and process many Linux distributions unmodified, for example, including Debian and Fedora .
Virtual servers are normally used by web hosting service providers because they allow a clean separation of different virtual customer machines and a separation of these machines from each other while at the same time pooling the computer resources. In order to get by with as little disk space as possible in such installations, the file system of each virtual server is set up as a copy-on-write hard link on a virtual file system. This hard link has special file system attributes which, if a change is detected, replace the file to be written with a real copy of the file written securely and transparently.
Linux-VServer exists in two different versions, a stable version V.2.2.x and a developer version V.2.3.x for the Linux kernel 2.6, and a stable version for the Linux kernel 2.4.
Comparable virtualization mechanisms
Other comparable virtualization technologies are OpenVZ , FreeBSD 's FreeBSD Jail method, Solaris Containers and FreeVPS (an early derivative ( fork ) of Linux-VServer).
advantages
- Virtual servers use the same system call interface and do not generate any additional load through emulation .
- The virtual servers do not have to be backed up by a non-transparent disk image , but can use a general, shared file system (using copy-on-write hard links). This makes backing up a virtual server easier and allows the available disk space to be used for several virtual servers.
- Processes within the virtual server run like normal processes on a computer system. This is far more efficient in terms of memory utilization and I / O load than the full emulation of a computer, which can no longer make unused main memory or disk space available to the host computer or other virtual servers.
- Processes within a virtual server are processed with the scheduler of the host computer, which allows the guest processes of the virtual server to run simultaneously on multiprocessor systems (SMP). Such an implementation for complete emulations of a computer would be expensive.
- The network connections are realized by packet separation instead of virtualization; here, too, additional packet processing is avoided.
disadvantage
- Linux VServer requires a modified operating system kernel on the host.
- All virtual servers use this same kernel and are therefore also susceptible to bugs and security holes it contains.
- Neither clustering nor process takeover are 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 are based on packet separation and not on virtualization, none of the virtual servers can set up their own internal routing tables or be used as a firewall computer.
- Some particularly hardware-specific system calls such as the real-time clock and parts of the / proc and / sys file system cannot be virtualized.
- Linux VServer does not yet allow I / O bandwidth to be allocated to individual virtual servers. This option is only available in the development versions, but not yet in the stable version.
See also
Web links
- Project website (English)
Individual evidence
- ↑ Release 0.30.215 . March 17, 2008 (accessed September 21, 2018).
- ↑ The vserver Open Source Project on Open Hub: Languages Page . In: Open Hub . (accessed on September 21, 2018).