Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE Guida di Installazione Scaricare il pdf (Pagina 47)

Chapter 2. The /proc File System 47

2.3.8.3. /proc/sys/kernel/

This directory contains a variety of different conﬁguration ﬁles that directly affect the operation of the

kernel. Some of the most important ﬁles include:

• acct — Controls the suspension of process accounting based on the percentage of free space

available on the ﬁle system containing the log. By default, the ﬁle looks like this:

4 2 30

The second value sets the threshold percentage of free space when logging will be suspended, while

the ﬁrst value dictates the percentage of free space required for logging to resume. The third value

sets the interval in seconds that the kernel polls the ﬁle system to see if logging should be suspended

or resumed.

• cap-bound — Controls the capability bounding settings, which provide a list of capabilities for any

process on the system. If a capability is not listed here, then no process, no matter how privileged,

can do it. The idea is to make the system more secure by ensuring that certain things cannot happen,

at least beyond a certain point in the boot process.

The various values that are possible here are beyond the scope of this manual, so consult the kernel

documentation for more information.

• ctrl-alt-del — Controls whether [Ctrl]-[Alt]-[Delete] will gracefully restart the computer us-

ing init (value 0) or force an immediate reboot without syncing the dirty buffers to disk (value

1).

• domainname — Allows you to conﬁgure the system’s domain name, such as su/jointfilesconvert/370363/bgenius.com.

• hostname — Allows you to conﬁgure the system’s host name, such as bob.su/jointfilesconvert/370363/bgenious.com.

• hotplug — Conﬁgures the utility to be used when a conﬁguration change is detected by the system.

This is primarily used with USB and Cardbus PCI. The default value of /sbin/hotplug should

not be changed unless you are testing a new program to fulﬁll this role.

• modprobe — Sets the location of the program to be used to load kernel modules when necessary.

The default value of /sbin/modprobe signiﬁes that kmod will call it to actually load the module

when a kernel thread calls kmod.

• msgmax — Sets the maximum size of any message sent from one process to another is set to

8192 bytes by default. You should be careful about raising this value, as queued messages between

processes are stored in non-swappable kernel memory. Any increase in msgmax would increase

RAM requirements for the system.

• msgmnb — Sets the maximum number of bytes in a single message queue. By default, 16384.

• msgmni — Sets the maximum number of message queue identiﬁers. By default, 16.

• osrelease — Lists the Linux kernel release number. This ﬁle can only be altered by changing the

kernel source and recompiling.

• ostype — Displays the type of operating system. By default, this ﬁle is set to Linux, and this

value can only be changed by changing the kernel source and recompiling.

• overflowgid and overflowuid — Deﬁnes the ﬁxed group ID and user ID, respectively, for use

with system calls on architectures that only support 16-bit group and user IDs.

• panic — Deﬁnes the number of seconds the kernel will postpone rebooting the system when a

kernel panic is experienced. By default, the value is set to 0, which disables automatic rebooting

after a panic.

• printk — This ﬁle control a variety of settings related to printing or logging error messages. Each

error message reported by the kernel has a loglevel associated with it that deﬁnes the importance of

the message. The loglevel values break down in this order:

• 0 — Kernel emergency. The system is unusable.

1 2 ... 42 43 44 45 46 47 48 49 50 51 52 ... 281 282

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Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE Guida di Installazione Pagina 47

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