chcpu

Disable one or more CPUs by their IDs

$ chcpu [[-d|--disable]] [1,3]

$ chcpu [[-e|--enable]] [1-3,5-7]

chcpu [options] [cpulist] command

-h, --help
    Display help and exit

-V, --version
    Output version information

-v, --verbose
    Enable verbose output

-i, --ignore-offline
    Ignore offlined CPUs in operations

-p, --cpu-list cpulist
    Specify comma-separated CPU list (alternative to positional arg)

--disable[=cpulist]
    Disable listed CPUs (prevent onlining)

--enable[=cpulist]
    Enable listed CPUs (allow onlining)

--offline[=cpulist]
    Take listed CPUs offline

--online[=cpulist]
    Bring listed CPUs online

--status[=cpulist]
    Print status of listed CPUs (online/offline)

The chcpu command is a utility from the util-linux package used to dynamically change the state of CPUs in a running Linux system. It supports enabling or disabling CPUs, bringing them online or offline, and querying their status. This is particularly useful for power management, performance tuning, testing multi-CPU configurations, or handling hardware faults.

chcpu interacts with the Linux kernel's CPU hotplug subsystem via sysfs (/sys/devices/system/cpu/). Offlining a CPU migrates its tasks to other CPUs and stops scheduling new ones on it, while onlining reverses this. Disabling prevents a CPU from being brought online, and enabling allows it.

Requires root privileges (use sudo). Not all systems support CPU hotplug; it depends on kernel configuration (CONFIG_HOTPLUG_CPU) and hardware (e.g., SMP systems). CPU 0 (bootstrap processor) typically cannot be offlined. Verbose mode provides detailed output on operations.

cpulist format: comma-separated ranges like 0-3,7,9-11. Use lscpu to list available CPUs.

Requires root privileges. CPU 0 usually cannot be offlined. Hotplug support varies by kernel/hardware. Offlining may fail if CPU has critical tasks or dependencies.

Format: cpu[,cpu]... or cpu-cpu[,cpu]... (e.g., 0-3,7)

Operates on /sys/devices/system/cpu/cpu*/online and /sys/devices/system/cpu/cpu*/uevent

Introduced in util-linux 2.26 (March 2014) to simplify CPU hotplug management via sysfs. Builds on kernel CPU hotplug feature added in Linux 2.6 (2003). Widely used in enterprise servers and HPC for dynamic resource control.

lscpu(1), taskset(1), numactl(1), cpuset(7)