GRUB badly broken during upgrade

[Tom H]

On Fri, Oct 5, 2012 at 7:20 PM, Kevin O'Gorman <kogorman at gmail.com> wrote:
> On Fri, Oct 5, 2012 at 4:08 PM, Tom H <tomh0665 at gmail.com> wrote:
>> On Fri, Oct 5, 2012 at 6:53 PM, Kevin O'Gorman <kogorman at gmail.com> wrote:
>>>
>>> Update: I researched GRUB a little. I can now get the grub rescue to
>>> restore its 'normal' module, and boot a rescue kernel, which I can get
>>> into a root console session of the just-upgraded Ubuntu.
>>> NOTE: here's where I'm really glad I give root a password. The kernel
>>> requires a root password for this to work.
>>
>> Please don't pollute the list with nonsense regarding single user mode
>> and enabling root in Ubuntu (for the second time).
>>
>> You're being prompted for root's password because you've enabled root.
>> If root's password's locked, you get a root prompt directly.
>
> If that's true, it's new and news to me. I clearly remember being in
> the hell of having this capability unavailable because root had no
> password. It was quite a while ago, but established this mind-set
> pretty firmly. Once I get this running again -- and I'm sure a normal
> boot will work -- I'll experiment with it and maybe change my ways.
>
> I also have to say I don't understand your use of the phrase "root's
> password's locked" -- I'm not aware of locking or unlocking it, just
> of setting a password where there did not appear to be one before.

Single-user logon may or may but not have been broken at some point in
some Ubuntu release (I've never come across this problem but I might
have needed to boot in single-user mode when it was broken) but, by
design, if root's password is locked, you're dropped to a root prompt.
Ubuntu also has a "friendly-recovery" package that's installed by
default and gives you a dialog box about single-user options but I
never use it.

The (mechanical not philosophical) reason that root is "disabled" on
Ubuntu is that the password field for the "root ..." line in
"/etc/shadow" is a "!" or a "*" (I've forgotten which it is but both
work). If you "enable" root and later want to "disable" it, you have
to run "passwd {-l | --lock}" and the password field for the "root
..." line in "/etc/shadow" will be prepended with a "!".