I have a KVM guest that I need to reset the password. If I use 'virsh console' to access the guest account, I'm able to update the shadow file with a new hash line like '$6$avdwsefs$In0A44PGN3xHczlF4qeF5wrVs6WmeCfTUYB1WZ1g6Co.fq62l5/0ZbrnGWbjhRQT598eAKDo/nMaW6iJCA3k2.'. If I reboot the guest account, the new password works. But if I mount the guest system in server and update the shadow file in /mnt directory, the password won't work. Both the old password hash and new password hash won't work after I modify shadow file in the mounted directory.
Update: Both the server system and vps guest system have centos6.4 and the latest update of glibc.