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--- linux_wiki:use_proc_sys_and_sysctl_to_modify_and_set_kernel_runtime_parameters [2016/09/18 16:37]
billdozor [Persistent Kernel Settings]
+++ linux_wiki:use_proc_sys_and_sysctl_to_modify_and_set_kernel_runtime_parameters [2019/05/25 23:50] (current)
@@ Line 4: / Line 4: @@
 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
+----
+====== Help ======
+Finding help in this section.
+  * Sysctl man page<code bash>man sysctl</code>
 ----
@@ Line 28: / Line 42: @@
 sysctl -w vm.swappiness=10
 sysctl vm.swappiness
+# Or
+sysctl -a | grep swappiness
 </code>
   * -w -> write
@@ Line 44: / Line 61: @@
   * Default system values: /usr/lib/sysctl.d/
-  * Persistent configuration over rides: /etc/sysctl.conf
+  * Persistent configuration over rides: /etc/sysctl.d/filename.conf
 \\
-Create entries in /etc/sysctl.conf
+Create entries in /etc/sysctl.d/mychanges.conf
 <code bash>
 vim /etc/sysctl.conf
@@ Line 57: / Line 74: @@
 Load settings from a file
 <code bash>
-sysctl -p <filename>
+sysctl -p /etc/sysctl.d/mychanges.conf
 </code>
   * If no file name is specified, defaults to: /etc/sysctl.conf
 \\
-**Note**: Starting in CentOS 7.2, some parameters (such as vm.swappiness) are set AFTER systemd-sysctl.service by the tuned service.
+Load all settings
+<code bash>
+sysctl --system
+</code>
+===== Tuned =====
+Tuned is a "dynamic adaptive system tuning daemon".
+  * **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 (/etc/tuned/tuned-main.conf)<code bash>....SNIP....
+# Whether to reapply sysctl from the e.g /etc/sysctl.conf, /etc/sysctl.d, ...
+# 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....</code>
+  * Either way; be aware of tuned and its potential to conflict with sysctl.
 \\
@@ Line 71: / Line 105: @@
 \\
-Location of tuned profiles: /usr/lib/tuned/
+  * Location of built in system tuned profiles: /usr/lib/tuned/
+  * Location of user defined profiles: /etc/tuned
+  * **Example**: Create a virtual-guest override file<code bash>mkdir /etc/tuned/virtual-guest
+cp /usr/lib/tuned/virtual-guest/tuned.conf /etc/tuned/virtual-guest/</code>
+    * Edit the over ride file (/etc/tuned/virtual-guest/tuned.conf), make any changes.
+    * Restart the tuned service<code bash>systemctl restart tuned</code>
 ----