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--- linux_wiki:use_proc_sys_and_sysctl_to_modify_and_set_kernel_runtime_parameters [2016/08/10 22:35]
billdozor [Runtime 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 36: / Line 53: @@
 echo "15" > /proc/sys/vm/swappiness
 </code>
+----
+====== Persistent Kernel Settings ======
+To make changes that are persistent across reboots...
+  * Default system values: /usr/lib/sysctl.d/
+  * Persistent configuration over rides: /etc/sysctl.d/filename.conf
+\\
+Create entries in /etc/sysctl.d/mychanges.conf
+<code bash>
+vim /etc/sysctl.conf
+net.ipv4.ip_forward = 1
+</code>
+\\
+Load settings from a file
+<code bash>
+sysctl -p /etc/sysctl.d/mychanges.conf
+</code>
+  * If no file name is specified, defaults to: /etc/sysctl.conf
+\\
+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.
+\\
+View the active tuned profile
+<code bash>
+tuned-adm active
+</code>
+\\
+  * 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>
 ----