Kernel Parameter Modification Flashcards
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Read the first 7 Kernel Parameter Modification flashcards as text
Which file would you edit to make the kernel parameter 'net.ipv4.ip_forward=1' persist across reboots on a systemd-based system?
Answer: /etc/sysctl.conf
/etc/sysctl.conf is the primary file for persistent kernel parameter settings that survive reboots.
What is the effect of running 'sysctl -w vm.swappiness=10'?
Answer: Changes swappiness only for the current session until reboot
The -w flag writes the value to the live kernel immediately but does not persist across reboots.
Which directory under /proc/sys corresponds to the sysctl key 'kernel.hostname'?
Answer: /proc/sys/kernel/hostname
Sysctl keys map to /proc/sys paths by replacing dots with slashes, so kernel.hostname → /proc/sys/kernel/hostname.
A sysadmin wants to apply all settings from /etc/sysctl.d/ without rebooting. Which command accomplishes this?
Answer: sysctl --system
'sysctl --system' loads settings from all standard sysctl configuration directories including /etc/sysctl.d/.
What does the kernel parameter 'kernel.dmesg_restrict=1' control?
Answer: Restricts dmesg output to privileged users only
When set to 1, kernel.dmesg_restrict prevents unprivileged users from reading the kernel ring buffer via dmesg.
Which sysctl parameter controls the maximum number of open file descriptors system-wide?
Answer: fs.file-max
fs.file-max sets the system-wide maximum number of file handles the kernel will allocate.
Drop-in files placed in /etc/sysctl.d/ must have which file extension to be processed by sysctl --system?
Answer: .conf
Only files ending in .conf inside /etc/sysctl.d/ are automatically read by 'sysctl --system'.
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