the /sys/devices/system/cpu/isolated file is null ,Node-exporter fails to start

[viviaiyc]

sfs|overlay|proc|procfs|pstore|rpc_pipefs|securityfs|selinuxfs|squashfs|sysfs|tracefs)$ panic: Couldn't create metrics handler: couldn't create collector: Unable to get isolated cpus: strconv.Atoi: parsing " (null)": invalid syntax

goroutine 1 [running]: main.newHandler(0x1, 0x28, {0xcef880, 0xc00004a4c0}) /app/node_exporter.go:69 +0x2ab main.main() /app/node_exporter.go:201 +0x128d

the /sys/devices/system/cpu/isolated file is null