You could use the passwd command to change a user’s password.
To do this you could try chroot from a live usb (the installation USB basically) of OpenMandriva or Any distro you want (i know this is an option but i honestly never used it to fix password problems myself). I think this would help if you cannot login at all, which i guess is your scenario since you say you tried CLI (using the Ctrl+Alt+function) combination, right?
MX Linux for example has a Chroot tool for fixing problems like this. You could check that out.
I am no expert so if you prefer, you could wait for someone else’s suggestion or check the chroot method online if you wish more information quickly.
I don’t know if you’re able to get in with recovery mode. I had this happeneing in the CLI like it would time out and stop recognizing my password. Then it happened with my login and I tried recovery mode. I got back in but had the same issue in the CLI. I don’t know of a permanent fix but I know now that when it happens in the CLI I can type $ sudo -k sudo -v
and it will force recognition of my password. Something to keep in mind if it happens again.
For completeness (because this is an obscure - albeit really cool - command) I’m just going to include some man page info to help anyone puzzle this out in the future:
man sudo
...
By running sudo with the -v option, a user can update the cached credentials without running a command.
...
-k, -‐reset‐timestamp
When used without a command, invalidates the user’s cached credentials for the current session. The next time sudo is run in the session, a password must be entered if the security policy requires authentication. By default, the sudoers policy uses a separate record in the credential cache for each terminal (or parent process ID if no terminal is present). This prevents the -k option from interfering with sudo commands run in a different terminal session.
See the timestamp_type option in sudoers(5) for more information. This option does not require a password, and was added to allow a user to revoke sudo permissions from a .logout file.
When used in conjunction with a command or an option that may require a password, this option will cause sudo to ignore the user’s cached credentials. As a result, sudo will prompt for a password (if one is required by the security policy) and will not update the user’s cached credentials.
So in this case (where there is a command) the “-k” tells the system to ignore any sudo credentials that you may have already typed (because you used sudo a command or 2 ago) and then the “-v” lets you just reset the sudo by itself
Otherwise you actually have to enter a command to go with your “sudo” invocation (like sudo ls /root)
In effect it’s like logging out and logging back in only for sudo.
or check the chroot method online if you wish more information quickly.