Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE Guida di Installazione Scaricare il pdf (Pagina 23)

Chapter 2.

The /proc File System

The Linux kernel’s primary functions are to control access to physical devices on the computer and to

schedule when and how processes interact with these devices. The /proc directory contains hierarchy

of virtual folders and ﬁles which represent the current state of the kernel. Viewing ﬁles within /proc

allows the user to peer into the kernel’s view of the system. In addition, the user can use these virtual

ﬁles to communicate conﬁguration changes to the kernel.

2.1. A Virtual File System

In Linux, everything is stored as a ﬁle. Most users are familiar with the two primary types of ﬁles, text

and binary. However, the /proc directory contains ﬁles that are not part of any ﬁle system associated

with any physical storage device connected to your system. Instead, the virtual ﬁles in /proc are part

of a virtual ﬁle system.

The virtual ﬁles in /proc have unique qualities. Most of them are 0 bytes in size. Yet when the ﬁle

is viewed, it can contain 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.

Both applications and system administrators can use /proc as a method of accessing information

about the state of the kernel, the attributes of the machine, the state of individual processes, and so on.

Most of the ﬁles in the directory, such as interrupts, meminfo, mounts, and partitions, provide

an up-to-the-moment glimpse of a system’s physical environment. Others, like file systems and

the /proc/sys/ directory provide software conﬁguration information.

To make things easier, ﬁles that contain information covering a similar topic are grouped into virtual

directories and sub-directories, such as /proc/ide/ for all physical IDE devices.

2.1.1. Viewing Virtual Files

By using cat, more, or less commands on the ﬁles within /proc, you can immediately access an

enormous amount of information about the system. For example, if you want to see what sort of CPU

your computer has, type cat cpuinfo and you will see something similar to the following:

processor : 0

vendor_id : AuthenticAMD

cpu family : 5

model : 9

model name : AMD-K6(tm) 3D+ Processor

stepping : 1

cpu MHz : 400.919

cache size : 256 KB

fdiv_bug : no

hlt_bug : no

f00f_bug : no

coma_bug : no

fpu : yes

fpu_exception : yes

cpuid level : 1

wp : yes

flags : fpu vme de pse tsc msr mce cx8 pge mmx syscall 3dnow k6_mtrr

bogomips : 799.53

1 2 ... 18 19 20 21 22 23 24 25 26 27 28 ... 281 282

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Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE Guida di Installazione Pagina 23

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