preconfigure an empty password for mysql via debconf-set-selections

Currently, it is possible to do this, but it's a little tricky.

You have to explicitly set quotes to mark an empty password, like this:

sudo debconf-set-selections <<< "mysql-server mysql-server/root_password password \"''\""

Just tested on Ubuntu 15.10, works like a charm.

The recommended approach for setting an empty password during mysql-server's package installation process using debconf-set-selections depends on the package version in hand.

• MySQL 5.7

  Although it's possible to configure the password to be empty, the installation process will automatically enable the authentication plugin auth_socket in such a case. Hence, the password-less login shall be conditioned on using UNIX socket based authentication (e.g. requiring the login to be made from the user account root on the local machine).

  • For the package provided by the MySQL APT repository:

    sudo debconf-set-selections <<< "mysql-community-server mysql-community-server/root-pass password "
    sudo debconf-set-selections <<< "mysql-community-server mysql-community-server/re-root-pass password "
    

  • For the package provided by the Ubuntu package repositories:

    sudo debconf-set-selections <<< "mysql-server mysql-server/root-password password "
    sudo debconf-set-selections <<< "mysql-server mysql-server/root-password_again password "
    

• MySQL 5.5 and MySQL 5.6

  The solution suggested by this answer should work, with a minor addition that confirms the empty password:

  sudo debconf-set-selections <<< "mysql-server mysql-server/root_password password \"''\""
  sudo debconf-set-selections <<< "mysql-server mysql-server/root_password_again password \"''\""
  

A fallback solution

If all approaches fail, it's possible to circumvent the issue and implicitly leave the password blank by preventing debconf from asking the user for a password altogether. Unfortunately, this applies to all questions, rather than just the password-related ones.

Here are two methods that achieve the desired result:

• Set debconf's frontend to noninteractive:

  DEBIAN_FRONTEND=noninteractive apt-get install [-y] [-q] mysql-server
  

• Set debconf's priority level to critical:

  DEBIAN_PRIORITY=critical apt-get install [-y] [-q] mysql-server
  

  This method is probably preferable as it permits the display of critical messages.

i think that your problem is that right before 'password' you need to add the word 'string' like this:

echo "mysql-server-5.5  mysql-server/root_password string password" | debconf-set-selections

btw this does the same thing but i think its cool:

debconf-set-selections <<< "mysql-server-5.5  mysql-server/root_password string password"