Since September 17, 1991, Linus Torvals officially announced the first official version of Linux & mdash; version 0.02. Up to now, the kernel version of Linux has undergone a series of changes. The time interval between the old and new versions is several months. Even for a few weeks, a very detailed look at this change can be found at http://ps.cus.umist.ac.uk/~rhw/kernel.versions.html.
We divided the kernel version into three phases, the first phase is 0.02 to 0.99.15j, the second phase is 1.0 to 1.2.x, and the third phase is 1.2. .x~2.xx. Generally speaking, a software must be given a version number of version 1.0 when it is theoretically complete or has no problem, and the version of Linux 2.0 and later has a larger change than the version of 1.2.x. Please see the site http ://www.linuxhq.com/content.
Since the birth of Linux, the Linux kernel has never stopped upgrading, from the 0.02 version released by Linus for the first time to the landmark version 2.2 of 1999, until the 2.4 version we are seeing now. Both have condensed a lot of hard work for Linux kernel developers. At present, Linux is widely used on various working platforms, including enterprise servers and personal computers, making Linux a strong competitor for Windows
.
The Linux kernel version analyzed in this book is version 2.4.16 of 2.4. So what are the characteristics of Linux 2.4, we can use four words to summarize, that is, "wide, new, fast, small".
1. Extensive support
· Full support for processor chips
: Linux 2.4 provides a large number of processor chip support. The original Linux can support multiple processor architectures, such as Intel x86, Motorola/IBM PowerPC, Compaq (DEC) Alpha, etc. Now, the three architectures of IA 64, S/390, and SuperH have been added. Support. For Intel's x86 series, AMD and Cyrix's line of processor products are also using x86 instructions, which are also well supported.
· Support for ISA Plug and Play Devices
: There used to be two different perspectives in the Linux Core Development Team. One is to support plug-and-play for ISA, and the other is opposed, thinking that support for plug-and-play is simply superfluous. So in the past, the common practice for plug-and-play setup in Linux was to manually configure Plug and Play devices using user-level tools such as isapn tools. The current kernel is different, and plug-and-play management is implemented at the kernel level. We can see that the system automatically detects and automatically configures Plug and Play devices at startup, for example, we can boot the system from a plug-and-play IDE controller.
· Broad File System Support:
Few OS
can support such a variety of file systems. Linux uses VFS (Virtual File System) technology and provides support for multiple file systems. From Linux 1.x to Linux 2.2, Linux already supports multiple file systems. Such as Windows 9x VFAT, DOS FAT, Mac OS HFS, OS/2 HPFS, Windows NT NTFS (NTFS support is still in beta), etc.; of course, including the high-performance Ext2 file system used by Linux itself. . The new version of Linux adds support for the UDF file system used by current DVDs and the XFS file system on SGI's IRIX system.
Using the SMB protocol in Windows to achieve shared access to "Network Neighborhood", the Linux 2.4 kernel will let you choose whether you want to use Windows 98/NT Load the drive down, you can also automatically detect the remote system type, so that your Linux works better in the LAN of the Windows environment.
For NFS (Network File System), Linux 2.4 supports the recently released NFS v3 version of the network file system.
·
Support for soft cats:
Soft cats are actually called WinModem, because of the existing This soft cat driver is built by software developed for Windows. This Modem is different from the general Modem processing method. Its DSP processing is not done at the hardware level, but is implemented by the CPU using software. Therefore, it is impossible to configure the Modem to access the Internet in the existing Linux. This support has already started in the Linux kernel.
2. New ideas
· New device management methods
: Linux 2.4 introduces I2O (Intelligent Input/Output) device driver management method. It does this by dividing the driver into two parts: one in the operating system module and the other in the hardware module. Part of the operating system module is independent, and part of the hardware module is dependent on the hardware structure. This new management approach makes Linux 2.4 better support for most ISA and PCI devices.
· Support for USB bus
: In recent years, USB (Universal Serial Bus) technology is one of the exciting things in the computer world. There have been a lot of devices using this interface, such as keyboards, mice, speakers, modems, and so on. The use of a USB interface makes it easier to install and use computer peripherals, which naturally becomes a trend. Today's Linux also supports devices with such bus interfaces.
· Binary Types of Binary Types:
Linux is the first to provide a built-in Java interpreter at the kernel level. One of the operating systems that support the execution of Java code. This has been implemented in the Linux 2.2 release. The Linux 2.4 version has been improved to change this support method to support for the "Misc" binary type. By using this type of binary code type, users can even use DOSEMU (MS DOS Simulator) or WINE (MS Windows Simulator) to run .exe or .com programs under DOS/Windows. The same user can also configure the Java bytecode run type.
· Kernel-level
Web server:
This kind of web server and the web we call the Apache user layer The server does not conflict. The HTTP request is first processed by the kernel-level web server, and if not processed, the request is submitted to the Apache user-level web server for processing. The concept and implementation like this is a must in the network operating system.
3. High performance
· Modifications to the virtual file system (VFS):
The 2.4 file system of Linux has modified the VFS errors, especially in the file cache management. In the past, file system cache management was built on a complex dual-buffer pool. This approach prevented developers from knowing when to synchronize the double-buffer pool. This processing method does not bring benefits to file processing, but increases the use of memory. Because of the synchronization of the double buffer system, the processing speed of the system is reduced. Now developers have modified this code to use a simple and efficient single buffer system to improve the processing efficiency of the file system.
· Support for high-end servers:
Linux 2.4 version of the kernel can support multiple under SMP (Symmetric Multiprocessor System) IO-APIC (Advanced Programmable Interrupt Controller for Input and Output) improves the efficiency of support for high-end servers.
Linux version 2.4 can support up to 10 IDE controllers. Previous versions of Linux could only support up to 4 ID controllers. Some powerful enterprise web servers are in need of such hardware support.
Linux version 2.4 can support MTRR (memory type range register) of Intel P6 and above chips, and ARR (address range) for non-Intel such as Cyrix 6x86, 6x86MX, MII Registers) are also well supported, which improves the performance of some high bandwidth devices.
The current kernel can support up to 4.2 billion users. Up to 4GB of memory can be supported on Intel architecture. And now the kernel can support up to 16 Ethernet cards, while supporting files with a maximum capacity of 2GB.
These features have made Linux's support for high-end devices improved.
· Support for high-speed networks:
Linux 2.4 supports high-speed network devices such as ATM network adapters, and is ready for further network development. ready. For low-end users, the combination of the PPP layer and the ISDN layer provided by Linux provides PPP on the parallel port and PPP support on the Ethernet.