pivot_root complains Invalid argument in centos 7.1

[guang...@gmail.com]

Hi all,

   i got a problem about pivot_root in centos 7.1, please anyone can give me a hand about that.

   heres is a simple  example

   

[19:05 root@host-10-10-10-200:/tmp] > cd /tmp/new_root/

[19:05 root@host-10-10-10-200:/tmp/new_root] > ll

total 16K

drwxr-xr-x 2 root root 4.0K May 14 15:07 bin

drwxr-xr-x 2 root root 4.0K May 14 14:45 lib

drwxr-xr-x 2 root root 4.0K May 14 14:54 lib64

drwxr-xr-x 2 root root 4.0K May 14 14:54 old_root

[19:05 root@host-10-10-10-200:/tmp/new_root] > cd ../../

[19:05 root@host-10-10-10-200:/] > mount -t aufs -o br:/tmp/new_root=rw none /mnt

[19:06 root@host-10-10-10-200:/] > ll mnt/

total 16K

drwxr-xr-x 2 root root 4.0K May 14 15:07 bin

drwxr-xr-x 2 root root 4.0K May 14 14:45 lib

drwxr-xr-x 2 root root 4.0K May 14 14:54 lib64

drwxr-xr-x 2 root root 4.0K May 14 14:54 old_root

[19:06 root@host-10-10-10-200:/] > cd mnt/

[19:06 root@host-10-10-10-200:/mnt] > pivot_root . old_root

pivot_root: failed to change root from `.' to `old_root': Invalid argument

[19:06 root@host-10-10-10-200:/mnt] > df -h

Filesystem     Type      Size  Used Avail Use% Mounted on

devtmpfs       devtmpfs  2.0G     0  2.0G   0% /dev

tmpfs          tmpfs     2.0G     0  2.0G   0% /dev/shm

tmpfs          tmpfs     2.0G  8.3M  2.0G   1% /run

tmpfs          tmpfs     2.0G     0  2.0G   0% /sys/fs/cgroup

/dev/vda1      ext4       38G   11G   25G  30% /

none           aufs       38G   11G   25G  30% /mnt

[19:17 root@host-10-10-10-200:/mnt] > 

thanks for any help.