Bug: OpenVZ migration with NFS version 4

There is bug for OpenVZ migration with NFS version 4


I mount the /vz and /etc/vz/conf directories to a NFS server to reduce the migration time.

I am able to suspend the container, but it give me error message when resuming it. If I unmount the two directories, problem would be resolved.

Here is the error message when I am using NFS

[root@sr2s1 /]# vzctl suspend 106

Setting up checkpoint...

suspend...

dump...

kill...

Checkpointing completed successfully

Container is unmounted

[root@sr2s1 /]# vzctl resume 106

Restoring container ...

Container is mounted

undump...

Setting CPU units: 1000

Restore error, undump failed: Not a directory

Error: can't open file /lib64/libnss_files-2.12.so

Error: do_rst_vma: rst_file: 107776

Error: do_rst_mm: failed to restore vma: -20

Error: do_rst_mm 183376

Error: rst_mm: -20

Container restore failed

Container is unmounted

The error message complains that the /vz/private/106/lib64/libnss_files-2.12.so file is not accessible, although I set up the correct access and ownership for that file. 

I solved this problem by downgrading the NFS version from 4 to 3. I think the NFS v4 does some security checks that prevents the vzctl resume to access the library files. 

How to downgrade NFS:

http://fengweizhang.blogspot.com/2014/01/downgrade-nfs-from-version-4-to-3.html