The typic error example:
Code:
[root@vz-ms mail]# vzctl start 7
Warning: configuration file for distribution cern-4-i386-minimal not found default used
Starting container ...
vzquota : (error) Quota on syscall for id 7: Device or resource busy
vzquota : (error)       Possible reasons:
vzquota : (error)       - Container's root is already mounted
vzquota : (error)       - there are opened files inside Container's private area
vzquota : (error)       - your current working directory is inside Container's
vzquota : (error)         private area
vzquota : (error)       Currently used file(s):

vzquota on failed [3]
[root@vz-ms mail]#
Solution:
Make sure there are no open files inside a container root and/or private area (and your current working directory is not inside a container root/private area) by running the following command on the hardware node (assuming there is a problem with the container #7):

Code:
[root@vz-ms mail]# lsof 2> /dev/null | grep /vz/
bash      10754     root  cwd       DIR        8,7     4096    2195493 /home/vz/private/7/home/coremail
lsof      11131     root  cwd       DIR        8,7     4096    2195493 /home/vz/private/7/home/coremail
egrep     11132     root  cwd       DIR        8,7     4096    2195493 /home/vz/private/7/home/coremail
lsof      11133     root  cwd       DIR        8,7     4096    2195493 /home/vz/private/7/home/coremail
[root@vz-ms mail]# kill -9 10754 11131 11132 11133

There are four processes which hold a directory inside the container 7 root/private area - revise and kill them all.

After killing all of them, the openvz virtual server is running well as before!