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linux_wiki:use_proc_sys_and_sysctl_to_modify_and_set_kernel_runtime_parameters [2018/03/30 00:48] billdozor [Tuned] |
linux_wiki:use_proc_sys_and_sysctl_to_modify_and_set_kernel_runtime_parameters [2019/05/25 23:50] |
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| - | ====== Use Proc Sys And Sysctl To Modify And Set Kernel Runtime Parameters ====== | ||
| - | |||
| - | **General Information** | ||
| - | |||
| - | Modifying runtime or persistent kernel parameters. | ||
| - | |||
| - | ---- | ||
| - | |||
| - | ====== Lab Setup ====== | ||
| - | |||
| - | The following virtual machines will be used: | ||
| - | * server1.example.com (192.168.1.150) -> Configure the kernel parameters here | ||
| - | |||
| - | ---- | ||
| - | |||
| - | ====== Runtime Kernel Settings ====== | ||
| - | |||
| - | Everything in this section are runtime ONLY changes; the values will go back to their original setting upon reboot. | ||
| - | |||
| - | \\ | ||
| - | View all tunable kernel parameters | ||
| - | <code bash> | ||
| - | sysctl -a | ||
| - | </ | ||
| - | |||
| - | \\ | ||
| - | View the configuration of a specific setting | ||
| - | <code bash> | ||
| - | sysctl vm.swappiness | ||
| - | </ | ||
| - | |||
| - | \\ | ||
| - | Write a runtime only configuration change and verify | ||
| - | <code bash> | ||
| - | sysctl -w vm.swappiness=10 | ||
| - | sysctl vm.swappiness | ||
| - | |||
| - | # Or | ||
| - | sysctl -a | grep swappiness | ||
| - | </ | ||
| - | * -w -> write | ||
| - | |||
| - | \\ | ||
| - | Alternative: | ||
| - | <code bash> | ||
| - | echo " | ||
| - | </ | ||
| - | |||
| - | ---- | ||
| - | |||
| - | ====== Persistent Kernel Settings ====== | ||
| - | |||
| - | To make changes that are persistent across reboots... | ||
| - | |||
| - | * Default system values: / | ||
| - | * Persistent configuration over rides: / | ||
| - | |||
| - | \\ | ||
| - | Create entries in / | ||
| - | <code bash> | ||
| - | vim / | ||
| - | |||
| - | net.ipv4.ip_forward = 1 | ||
| - | </ | ||
| - | |||
| - | \\ | ||
| - | Load settings from a file | ||
| - | <code bash> | ||
| - | sysctl -p / | ||
| - | </ | ||
| - | * If no file name is specified, defaults to: / | ||
| - | |||
| - | \\ | ||
| - | Load all settings | ||
| - | <code bash> | ||
| - | sysctl --system | ||
| - | </ | ||
| - | |||
| - | ===== Tuned ===== | ||
| - | |||
| - | Tuned is a " | ||
| - | |||
| - | * **Notes** | ||
| - | * Starting in EL 7.2, some parameters (such as vm.swappiness) are set AFTER systemd-sysctl.service by the tuned service. | ||
| - | * In EL 7.4, it appears that tuned defaults to honor sysctl (/ | ||
| - | # Whether to reapply sysctl from the e.g / | ||
| - | # If enabled these sysctls will be re-appliead after Tuned sysctls are | ||
| - | # applied, i.e. Tuned sysctls will not override system sysctls. | ||
| - | reapply_sysctl = 1 | ||
| - | ....SNIP....</ | ||
| - | |||
| - | \\ | ||
| - | View the active tuned profile | ||
| - | <code bash> | ||
| - | tuned-adm active | ||
| - | </ | ||
| - | |||
| - | \\ | ||
| - | * Location of built in system tuned profiles: / | ||
| - | * Location of user defined profiles: /etc/tuned | ||
| - | * **Example**: | ||
| - | cp / | ||
| - | * Edit the over ride file (/ | ||
| - | * Restart the tuned service< | ||
| - | |||
| - | ---- | ||