Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE Guida di Installazione Scaricare il pdf (Pagina 48)

48 Chapter 2. The /proc File System

• 1 — Kernel alert. Action must be taken immediately.

• 2 — Condition of the kernel is considered critical.

• 3 — General kernel error condition.

• 4 — General kernel warning condition.

• 5 — Kernel notice of a normal but signiﬁcant condition.

• 6 — Kernel informational message.

• 7 — Kernel debug-level messages.

Four values are found in the printk ﬁle:

6 4 1 7

Each of these values deﬁnes a different rule for dealing with error messages. The ﬁrst value, called

the console loglevel, deﬁnes the lowest priority of messages that will be printed to the console.

(Note that, the lower the priority, the higher the loglevel number.) The second value sets the default

loglevel for messages without an explicit loglevel attached to them. The third value sets the lowest

possible loglevel conﬁguration for the console loglevel. The last value sets the default value for the

console loglevel.

• rtsig-max — Conﬁgures the maximum number of POSIX realtime signals that the system may

have queued at any one time. The default value is 1024.

• rtsig-nr — The current number of POSIX realtime signals queued by the kernel.

• sem — This ﬁle conﬁgures semaphore settings within the kernel. A semaphore is a System V IPC

object that is used to control utilization of a particular process.

• shmall — Sets the total amount of shared memory that can be used at one time on the system, in

bytes. By default, this value is 2097152.

• shmmax — Sets the largest shared memory segment size allowed by the kernel, in bytes. By default,

this value is 33554432. However, the kernel supports much larger values than this.

• shmmni — Sets the maximum number of shared memory segments for the whole system. By de-

fault, this value is 4096

• sysrq — Activates the System Request Key, if this value is set to anything other than the default

of 0.

• threads-max — Sets the maximum number of threads to be used by the kernel, with a default

value of 2048.

• version — Displays the date and time the kernel was last compiled. The ﬁrst ﬁeld in this ﬁle, such

as #3, relates to the number of times a kernel was built from the source base.

The random directory stores a number of values related to generating random numbers for the kernel.

2.3.8.4. /proc/sys/net/

This directory contains assorted directories concerning various networking topics. Various conﬁgura-

tions at the time of kernel compilation make available different directories here, such as appletalk,

ethernet, ipv4, ipx, and ipv6. Within these directories, you can adjust the assorted networking

values for that conﬁguration on a running system.

Given the wide variety of possible networking options available with Linux and the great amount of

space required to discuss them, only the most common /proc/sys/net/ directories will be dis-

cussed.

The core directory contains a variety of settings that control the interaction between the kernel and

networking layers. The most important ﬁles there are:

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Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE Guida di Installazione Pagina 48

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