Another problem that is commonly encountered is that when a volume is detached from an instance, it doesn't get attached again. To resolve this problem, you must change the device name on the nova-attach command. The VM might not clean up after a nova-detach command runs. 

A volume may also fail to attach with the error, systool is not installed:

WARNING nova.virt.libvirt.utils [req-1139818-12je-8f39f-c0f8-kf983nkf984kf0
admin admin|req-1139818-12je-8f39f-c0f8-kf983nkf984kf0 admin admin] systool is not installed
ERROR nova.compute.manager [req-1139818-12je-8f39f-c0f8-kf983nkf984kf0 admin
admin|req-1139818-12je-8f39f-c0f8-kf983nkf984kf0 admin admin]
[instance: ksdf09834-sdf35-4er3a-d323-234lw34epwe0c|instance: s87324hf9-8c3f-234a-be9b-47c97626555c]
Failed to attach volume 394wer23-23ra-2342-34f2a-2349ske934ser at /dev/vdk.

In this case, simple install the sysfsutils package on the compute host:

# apt-get install sysfsutils

The previous discussion gives your a brief understanding of the approach to troubleshooting the Nova Compute service. The logs usually have sufficient error messages to indicate the root cause of the problem.

Lets move on to the OpenStack Block Storage service and see how we can troubleshoot it.