func (pool *Pool) Offline(force bool, devs ...string) (err error) {
	return pool.offline(false, force, devs...)
}
Offline Take the device/s in offline state
package zfs
import "C"
import (
	"fmt"
	"unsafe"
)
func (pool *Pool) Online(expand bool, devs ...string) (err error) {
	cflags := C.int(0)
	if expand {
		cflags = C.ZFS_ONLINE_EXPAND
	}
	for _, dev := range devs {
		csdev := C.CString(dev)
		var newstate VDevState
		if newstate = VDevState(C.set_zpool_vdev_online(pool.list, csdev, cflags)); newstate != VDevStateUnknown {
			if newstate != VDevStateHealthy {
				err = fmt.Errorf(
					"Device '%s' onlined, but remains in faulted state",
					dev)
			}
		} else {
			err = LastError()
		}
		C.free(unsafe.Pointer(csdev))
	}
	return
}