Hi there, I created a before_set_num_of_cpus hook: # more /usr/libexec/vdsm/hooks/before_set_num_of_cpus/before.py #!/usr/bin/python import os import sys if os.environ.has_key('never_existed'): sys.stderr.write('cantsetcpu: before_cpu_set: cannot set cpu.\n') sys.exit(2) else: sys.stdout.write('hook ok.\n') sys.exit(0) But I cannot find the message "hook ok" in engine.log or vdsm.log, where to find it? Thank you very much. Thank you, -Zhen