Invalid username or password, please try again. An issue in a ubuntu VPS

After creation or migrating the VPS to a new node, you may face issues related to the Parallels Power Panel of the Container, root password not accepted for the Power Panel and the following error message is shown:

“Invalid username or password, please try again.”

SSH working though.

Reason : The default policy in Ubuntu 8.10 seems to be forced to use SHA512 hashing. For example, in Debian 5.0 (and previous versions of Debian, Ubuntu) it was set to MD5.

# grep '^[^#]' /etc/pam.d/common-password
password required pam_unix.so nullok obscure min=4 max=8 md5

Fix : It is sufficient to update the file /etc/pam.d/common-password and reset the ‘root’ password inside a Container.

# vzctl enter containerID
# sed '/^password.*pam_unix.so.*sha512/ s~sha512~md5~' -i etc/pam.d/common-password

After that this file /etc/pam.d/common-password will contain these lines,

# grep '^[^#]' /etc/pam.d/common-password
password [success=1 default=ignore] pam_unix.so obscure md5
password requisite pam_deny.so
password required pam_permit.so

and reset the root password by

# passwd root
Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully

Now, try to access the Power Panel by https://serverIP:4643.

Should be fine now.