Quick methods to read what features your running kernel was built with. 29.12.2025 | reading time: 2 min Want to know which features your running kernel was built with? This quick guide shows how to read the kernel configuration on a live system so you can answer that question fast. Live system check If the running kernel exported its config he can try: ```bash zcat /proc/config.gz | grep CONFIG_PREEMPT``` which often prints a line like ```CONFIG_PREEMPT=y```; if that file is missing check the installed config with ```bash grep -i CONFIG_PREEMPT /boot/config-$(uname -r)``` which yields similar output for packaged kernels. From compressed files to source Distributions may store configs compressed as gz or xz in /boot, so use `zcat` or `xzcat` accordingly; when you have the kernel source available the helper `scripts/extract-ikconfig` can pull an embedded config and `scripts/config --state CONFIG_SYMBOL` reports a symbol's state directly from a .config file. Interpreting what you see A value of "=y" means built-in, "=m" means built as a module and absent or "# CONFIG_FOO is not set" means disabled; remember that a module present in /lib/modules does not imply the feature was built-in and `modinfo` can show module parameters at runtime. Extra checks and edge cases Some kernels are built without IKCONFIG, so no /proc/config.gz will exist and the only truth may be the package's /boot/config file or the kernel source tree; also note that runtime tunables exposed via sysctl are not the same as build options, which are fixed at compile time. Try editing and rebuilding To change options work in a kernel source tree with `make menuconfig` or `make nconfig`, then rebuild; experimenting in a VM makes this safe and shows directly how configuration affects available modules and features. Where to go from here Inspecting configs opens a path to learning how features affect performance, security and hardware support; explore building a custom kernel to see the impact firsthand and consider formal study to deepen skills. Join Bits & Bytes Academy First class LINUX exam preparation. utilities boot-process troubleshooting
