MythTV setup failed with "Cannot login"

Thanks for the bug report. It looks like for some reason MySQL failed to start during install, causing it to not be properly configured.

Mar 3 11:04:30 ubuntu ubiquity: Rather than invoking init scripts through /etc/init.d, use the service(8)
Mar 3 11:04:30 ubuntu ubiquity: utility, e.g. service mysql stop
Mar 3 11:04:30 ubuntu ubiquity:
Mar 3 11:04:30 ubuntu ubiquity: Since the script you are attempting to invoke has been converted to an
Mar 3 11:04:30 ubuntu ubiquity: Upstart job, you may also use the stop(8) utility, e.g. stop mysql
Mar 3 11:04:58 ubuntu ubiquity: Rather than invoking init scripts through /etc/init.d, use the service(8)
Mar 3 11:04:58 ubuntu ubiquity: utility, e.g. service mysql start
Mar 3 11:04:58 ubuntu ubiquity:
Mar 3 11:04:58 ubuntu ubiquity: Since the script you are attempting to invoke has been converted to an
Mar 3 11:04:58 ubuntu ubiquity: Upstart job, you may also use the start(8) utility, e.g. start mysql
Mar 3 11:04:59 ubuntu ubiquity: mysql start/running, process 9378
Mar 3 11:04:59 ubuntu /etc/mysql/debian-start[9398]: Upgrading MySQL tables if necessary.
Mar 3 11:04:59 ubuntu kernel: [ 347.323752] non-accessible hardlink creation was attempted by: mysqld (fsuid 102)
Mar 3 11:04:59 ubuntu kernel: [ 347.324870] non-accessible hardlink creation was attempted by: mysqld (fsuid 102)
Mar 3 11:04:59 ubuntu kernel: [ 347.325538] non-accessible hardlink creation was attempted by: mysqld (fsuid 102)
Mar 3 11:04:59 ubuntu kernel: [ 347.326484] non-accessible hardlink creation was attempted by: mysqld (fsuid 102)
Mar 3 11:04:59 ubuntu kernel: [ 347.327078] non-accessible hardlink creation was attempted by: mysqld (fsuid 102)
Mar 3 11:04:59 ubuntu kernel: [ 347.331348] non-accessible hardlink creation was attempted by: mysqld (fsuid 102)
Mar 3 11:04:59 ubuntu kernel: [ 347.332049] non-accessible hardlink creation was attempted by: mysqld (fsuid 102)
Mar 3 11:04:59 ubuntu kernel: [ 347.336594] non-accessible hardlink creation was attempted by: mysqld (fsuid 102)
Mar 3 11:04:59 ubuntu kernel: [ 347.337399] non-accessible hardlink creation was attempted by: mysqld (fsuid 102)
Mar 3 11:04:59 ubuntu kernel: [ 347.337823] non-accessible hardlink creation was attempted by: mysqld (fsuid 102)
Mar 3 11:04:59 ubuntu /etc/mysql/debian-start[9401]: /usr/bin/mysql_upgrade: the '--basedir' option is always ignored
Mar 3 11:04:59 ubuntu /etc/mysql/debian-start[9401]: Looking for 'mysql' as: /usr/bin/mysql
Mar 3 11:04:59 ubuntu /etc/mysql/debian-start[9401]: Looking for 'mysqlcheck' as: /usr/bin/mysqlcheck
Mar 3 11:04:59 ubuntu /etc/mysql/debian-start[9401]: Running 'mysqlcheck' with connection arguments: '--port=3306' '--socket=/var/run/mysqld/mysqld.sock' '--host=localhost' '--socket=/var/run/mysqld/mysqld.sock' '--host=localhost' '--socket=/var/run/mysqld/mysqld.sock'
Mar 3 11:04:59 ubuntu /etc/mysql/debian-start[9401]: Running 'mysqlcheck' with connection arguments: '--port=3306' '--socket=/var/run/mysqld/mysqld.sock' '--host=localhost' '--socket=/var/run/mysqld/mysqld.sock' '--host=localhost' '--socket=/var/run/mysqld/mysqld.sock'
Mar 3 11:04:59 ubuntu /etc/mysql/debian-start[9401]: mysql...

This is suspected to be caused by apparmour, which might make it a duplicate of https://bugs.launchpad.net/ubuntu/+source/apparmor/+bug/727478

The non accessible hardlink errors go away if you run

  sysctl -w kernel.yama.protected_nonaccess_hardlinks=0

Before the myth-install-type page. Doesn't fix the second set of problems though.

So there's two distinct problems happening here. The first is fixed by the solution in comment #5. This may not be the proper solution, but it's functional for now.

The second is caused by upstart growing support to manage chroot jobs. The chroot job gets invoked in this case with mysqld.sock outside the chroot. This means that dpkg-reconfigure mythtv-database doesn't have access to it.

This bug was fixed in the package mythbuntu-live-autostart - 0.54-0ubuntu1

---------------
mythbuntu-live-autostart (0.54-0ubuntu1) natty; urgency=low

  * Fix spawning mysql in the install time chroot (LP: #728371)
    - The first fix turns off a kernel security feature for hardlinks
      temporarily, preventing a barage of errors as mysql is bootstrapped
    - The second stops the upstart job being managed from the chroot.
    - It's respawned manually in the chroot so processes in the chroot can
      still access it.
 -- Mario Limonciello <email address hidden> Fri, 04 Mar 2011 00:47:39 -0600