Disabling RHEL online CPU on Azure cloud throws an error

Solution Verified - Updated -


  • Disabling online CPU (RHEL VM) on azure throws an error.
  • Provision Standard DS series rhel instance on Azure with RHEL 7.2 and RHEL 6.8 version . While disabling some active/online CPU's in Azure RHEL, it throws below errors.
[root@XXXX ~]# echo 0 > /sys/devices/system/cpu/cpu19/online
-bash: echo: write error: Function not implemented
[root@XXXX ~]# cat /sys/devices/system/cpu/online
  • Following scenarios are executed to confirm this issue and found below results:
a) Using maxcpus parameter : Add kernel parameter maxcpus=N at boot time
b) Disabling CPU Online : At runtime disable cpu cores online via command line.

RHEL    max_cpus=1      cpu/online/offline (echo 0 > /sys/devices/system/cpu/cpu1/online)
6.7 no panic, 1 cpu     yes (hangs)
6.8 no panic, 1 cpu     no (write error: Function not implemented)
7.2 panic                no (write error: Function not implemented)


  • Azure cloud ARM mode
  • RHEL 6.8+
  • RHEL 7.2+

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