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60 Chapter 4:The /proc Filesystem -r--r--r-1 root -r--r--r-1 root -r--r--r-1 root [root@bleach /]# root root root 0 May 0 May 0 May 3 11:42 execdomains 3 11:42 fb 3 11:42 filesystems The /proc virtual files exhibit some interesting qualities. First, most of them are 0 bytes in size. However, when the file is viewed, it likely contains quite a bit of information. In addition, most of their time and date settings reflect the current time and date, meaning that they are constantly changing. Various programs use the /proc filesystem to discover the parameters of a system so that they can provide better performance and deliver more features. In addition, a system administrator can use /proc as an easy method of accessing information about the state of the kernel, the attributes of the machine, the states of individual processes, and more. Most of the files in this directory, such as interrupts, meminfo, mounts, and partitions, provide an up-to-the-moment glimpse of a system’s environment. To make things easier, files that contain information covering a similar topic are grouped into virtual directories and sub-directories, such as /proc/ide. 4.1.1 Viewing Virtual Files By using cat, more, or less commands in combination with the files within /proc, you can immediately access an enormous amount of information about the system. As an example, if you want to see how the memory registers are currently assigned on your computer: [root@bleach /]# cat /proc/iomem 00000000-0009fbff : System RAM 0009fc00-0009ffff : reserved 000a0000-000bffff : Video RAM area 000c0000-000c7fff : Video ROM 000f0000-000fffff : System ROM 00100000-03ffcfff : System RAM 00100000-002557df : Kernel code 002557e0-0026c80b : Kernel data 03ffd000-03ffefff : ACPI Tables 03fff000-03ffffff : ACPI Non-volatile Storage dc000000-dfffffff : S3 Inc. ViRGE/DX or /GX e3000000-e30000ff : Lite-On Communications Inc LNE100TX e3000000-e30000ff : eth0 e4000000-e7ffffff : Intel Corporation 440BX/ZX - 82443BX/ZX Host bridge ffff0000-ffffffff : reserved [root@bleach /]# Or (and more usefully), if were connecting to an unknown machine and wanted to know its CPU type and speed, you can use the following command:
