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Red Hat Enterprise Linux Troubleshooting Guide by Benjamin Cane

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Kernel tunables

The Linux Kernel itself can set limitations on a system as well. These limits are defined based on kernel parameters. Some of these parameters are static and cannot be changed during runtime; while others can. When a kernel parameter can be changed during runtime this is called a tunable parameter.

We can see both static and tunable kernel parameters and their current values by using the sysctl command:

# sysctl -a | head
abi.vsyscall32 = 1
crypto.fips_enabled = 0
debug.exception-trace = 1
debug.kprobes-optimization = 1
dev.hpet.max-user-freq = 64
dev.mac_hid.mouse_button2_keycode = 97
dev.mac_hid.mouse_button3_keycode = 100
dev.mac_hid.mouse_button_emulation = 0
dev.parport.default.spintime = 500
dev.parport.default.timeslice = ...

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