Kubuntu 15.10 & ecryptfs & change password

[Duncan]

Igor Mironchik posted on Wed, 09 Dec 2015 16:48:43 +0300 as excerpted:

> Hi folks,
> 
> I found, probably, strange bug... I had Kubuntu 15.10 with ecryptfs on
> my $HOME directory. Once I decided to change password for my user. I
> went to the System Settings and there changed password, rebooted... And
> I couldn't login to my Kubuntu. I saw login screen, entered new
> password, pressed Enter... Screen flashed and went back to login screen.
> And this happened until I returned my password to the old one from the
> command line...
> 
> Is it a known bug?

Appears to me (educated guess based on posted description of the problem) 
that Kubuntu most likely used the same user password both as a login 
password and as the encryption passphrase on your encrypted user $HOME 
dir.  Not unreasonable in itself, but if it also automatically passed the 
login password to the decryption routine behind the scenes, as it 
evidently does, then you either have to use the proper and likely ubuntu/
kubuntu-specific method to change password so both are changed at the 
same time, or separately manually change both at the same time using 
normal methods.

You used one of the normal methods to change your login password, but 
didn't also change the encryption passphrase at the same time, either 
using the normal method for separately changing it, or using the approved 
method for changing both at once, so when you logged in, the login worked 
but the decryption didn't because it was still set to the old password.

But I'm not a kubuntu/ubuntu user (or debian either, for that matter) so 
wouldn't know about their distro-specific tools, and I'm not sufficiently 
knowledgeable on the generic encryption tools side to know what generic 
command you'd invoke to separately change the encryptfs passphrase 
either, so while I can guess at the problem based on the description and 
hopefully point you in the direction of a fix, I can't directly tell you 
what that fix might be.

But pointing you in the right direction should get you further than you 
were, at least, so it's progress. =:^)  If that's not sufficient and you 
don't get more specific help here from another poster, I'd suggest 
posting the same question to the Ubuntu/Kubuntu forums/lists/whatever, as 
they're more likely to know the likely distro-specific tools to change 
both at once.

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman

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