[openstack-dev] [nova][NFS] Inexplicable utime permission denied when launching instance

Erlon Cruz sombrafam at gmail.com
Wed Oct 24 12:41:20 UTC 2018

PS. Don't forget that if you change or disable AppArmor you will have to
reboot the host so the kernel gets reloaded.

Em qua, 24 de out de 2018 às 09:40, Erlon Cruz <sombrafam at gmail.com>

> I think that there's a change that AppArmor is blocking the access. Have
> you checked the dmesg messages related with apparmor?
> Em sex, 19 de out de 2018 às 09:38, Neil Jerram <neil at tigera.io> escreveu:
>> Wracking my brains over this one, would appreciate any pointers...
>> Setup: Small test deployment with just 3 compute nodes, Queens on Ubuntu
>> Bionic. The first compute node is an NFS server for
>> /var/lib/nova/instances, and the other compute nodes mount that as NFS
>> clients.
>> Problem: Sometimes, when launching an instance which is scheduled to one
>> of the client nodes, nova-compute (in imagebackend.py) gets Permission
>> Denied (errno 13) when calling utime to touch the timestamp on the instance
>> file.
>> Through various bits of debugging and hackery, I've established that:
>> - it looks like the problem never occurs when this is the call that
>> bootstraps the privsep setup; but it does occur quite frequently on later
>> calls
>> - when the problem occurs, retrying doesn't help (5 times, with 0.5s in
>> between)
>> - the instance file does exist, and is owned by root with read/write
>> permission for root
>> - the privsep helper is running as root
>> - the privsep helper receives and executes the request - so it's not a
>> problem with communication between nova-compute and the helper
>> - root is uid 0 on both NFS server and client
>> - NFS setup does not have the root_squash option
>> - there is some AppArmor setup, on both client and server, and I haven't
>> yet worked out whether that might be relevant.
>> Any ideas?
>> Many thanks,
>>       Neil
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