红帽全球峰会第 5 章 Configuring kernel parameters at runtime
As a system administrator, you can modify many facets of the Red Hat Enterprise Linux kernel’s behavior at runtime. Configure kernel parameters at runtime by using the sysctl command and by modifying the configuration files in the /etc/sysctl.d/ and /proc/sys/ directories.
Configuring kernel parameters on a production system requires careful planning. Unplanned changes can render the kernel unstable, requiring a system reboot. Verify that you are using valid options before changing any kernel values.
For more information about tuning kernel on IBM DB2, see Tuning Red Hat Enterprise Linux for IBM DB2.
5.1. What are kernel parameters
Kernel parameters are tunable values that you can adjust while the system is running. Note that for changes to take effect, you do not need to reboot the system or recompile the kernel.
The difference between kernel parameters and kernel command line parameters is; Kernel parameters can configure the Linux kernel with all the options, while kernel command line parameters are the specific arguments passed to the kernel during boot, allowing runtime configuration without kernel recompilation.
It is possible to address the kernel parameters through:
-
The
sysctlcommand -
The virtual file system mounted at the
/proc/sys/directory -
The configuration files in the
/etc/sysctl.d/directory
Tunables are divided into classes by the kernel subsystem. Red Hat Enterprise Linux has the following tunable classes:
| Tunable class | Subsystem |
|---|---|
|
| Execution domains and personalities |
|
| Cryptographic interfaces |
|
| Kernel debugging interfaces |
|
| Device-specific information |
|
| Global and specific file system tunables |
|
| Global kernel tunables |
|
| Network tunables |
|
| Sun Remote Procedure Call (NFS) |
|
| User Namespace limits |
|
| Tuning and management of memory, buffers, and cache |
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