There are two main reasons why mysql_secure_installation might fail with a permissions issue:

1. Incorrect Authentication Plugin: By default, some MySQL installations might use the auth_socket plugin, which doesn't require a password by default. mysql_secure_installation expects a password and won't work with this setup.
2. Insufficient Privileges: Even with a password-based plugin, your user account might lack the necessary privileges to modify root user access. This could be due to:

• You’re not logged in as the root user.
• The root user doesn’t have the required permissions (unlikely, but possible).

Are you using Digital Ocean?

I had this issue when trying to run this command after installing the ghost 1-click installer.

When you’re logged into Digital Ocean as root run the commands shown below:

$ cat ~/.digitalocean_password # see the password, then do: $ sudo mysql_secure_installation

Configuring DigitalOcean 1-Click Ghost installation.

Please wait a minute while your 1-Click is configured.

Once complete, you are encouraged to run mysql_secure_installation to ready
your server for production.

Then enter the password that was shown in the bash console.

You also will have to switch to the ghost-mgr user to manage Ghost via the CLI:

sudo -i -u ghost-mgr

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