aznfs does not read entry in/etc/hosts

[Abbott-fu]

We use aznfs to mount a storage blob and we enabled private endpoint for the storage account, we hope to use the private endpoint. Then we add an entry (private end point IP -> stroage blob FQDN ) in /etc/hosts . But aznfs still uses DNS to lookup ip of the storage account, aznfs does not read entry in /etc/hosts. Is it by design.

[linuxsmiths]

Thanks for reporting @Abbott-fu!
Yes, this is deliberate. Note that the primary task of the aznfs mount helper is to detect IP changes due to migration. If it were to query fqdn->ip mapping from a static source like /etc/hosts it won't be able to detect the change in IP due to migration (etc) and hence won't work correctly.
Hope this helps!

[coconutservices]

We also have this issue, our DNS structure and hybrid architecture pose a lot of DNS challenges enterprise wide.

When using blobfuse, i use a script to do a nslooklup against another DNS and have it update the hosts file to accommodate the IP address, and then start the mount with blobfuse.

We would like to start using this tool, would it be possible to either give a parameter to disable the lookup or an override parameter of some type? We are definitely not the only organization in this situation, it can be very crippling.

Thanks!

[linuxsmiths]

If you cannot use realtime DNS for detecting IP address changes, you can use private endpoint which provides a stable IP across migrations.
Unfortunately, NFS clients are different from REST clients like blobfuse. While REST clients use the endpoint FQDN (which is stable), NFS clients do the DNS lookup only on mount and after that use the IP for reconnect. So, we either need a stable IP (that private endpoint provides) or we monitor IP address change and let NFS client know.

[JerryMWeeks]

Hi we are experiencing the same.

When you add a private endpoint from storage in the same subscription to 2 different vnets, the .privatelink.blob.core.windows.net records DNS gets overwritten, and does not seem to support 2 sets of IP addresses (although this is still being reviewed - awaiting reboot of our development servers after today's hacking!).

During addition of a private end point on storage you get offered

• use standard private dns,
• use your own dns,
• use no dns and resolve through hosts.

With domain registered VMs the own DNS option gets blurry, and when I tried aznfs appears to expect blob.core.windows.net mystorage.mydomain.eg fails - although we are investigating:

Not a valid Azure Blob NFS endpoint: mystorage.mydomain.eg!
Must be of the form 'account.blob.core.windows.net'!
For isolated environments, must set the environment variable AZURE_ENDPOINT_OVERRIDE to the appropriate endpoint suffix!

hosts would be far easier, and is normally supported in private endpoints.

[JerryMWeeks]

AZURE_ENDPOINT_OVERRIDE
We'll keep trying!

export AZURE_ENDPOINT_OVERRIDE=mydomain.eg
[mylinuxaccount@developervm ~]$ sudo mount /nfsdata

Not a valid Azure Blob NFS endpoint: mystorage.mydomain.eg!
Must be of the form 'account.blob.core.windows.net'!
For isolated environments, must set the environment variable AZURE_ENDPOINT_OVERRIDE to the appropriate endpoint suffix!

[JerryMWeeks]

AZURE_ENDPOINT_OVERRIDE

Well that appears to conclude that - seems AZURE_ENDPOINT_OVERRIDE might not quite behave - or have we missed something?

export AZURE_ENDPOINT_OVERRIDE=mystorage.mydomain.eg
[[mylinuxaccount@developervm ~]$ sudo mount /nfsdata

Not a valid Azure Blob NFS endpoint: mystorage.mydomain.eg!
Must be of the form 'account.blob.core.windows.net'!
For isolated environments, must set the environment variable AZURE_ENDPOINT_OVERRIDE to the appropriate endpoint suffix!

For reference fstab - domain anonymized naturally!
mystorage.mydomain.eg:/mystorage/backkupdev /nfsdata aznfs defaults,sec=sys,vers=3,nolock,proto=tcp,nofail,_netdev 0 0

[JerryMWeeks]

Can you provide an example of this, I cannot make out what this should become, it seems to imply that your own DNS needs to be able to use .core.

AZNFS-mount/src/mountscript.sh

Line 208 in 4ce66f0

eecho "Must be of the form 'account.$AZ_PREFIX.core.$AZURE_ENDPOINT_OVERRIDE'!"

eecho "Must be of the form 'account.$AZ_PREFIX.core.$AZURE_ENDPOINT_OVERRIDE'!"