su - Authentication failure - reinstall fedora ?

[Tod Merley]

Hi Angelo!

Most of the time that I have ever had problems with passwords it turned out
to actually be problems with my keyboard. So now, from time to time, with
the power off I invert the keyboard and while tilting it in several
directions operate the keys (sort of tapping from underneath) and then
spray - from underneath from several angles - Electronics compressed gas
duster air spray (e.g. Dust-Off). The idea is to get the gunk that normally
gets into the keyboard and under the keys out of there so that they can
work consistently.  You really do need that for passwords.

But looking at the second group of problems that cropped up as you tried to
boot into single user mode, well, my attention turns next to your disk (but
memory may be easier to check).  Do a memory check if you can (often a boot
menu option).  Then, assuming your disk is the normal spinning disk type
(not an SSD) use fsck and/or badblocks to test the health of the disk.  The
old spinning disks tend to fail in a specific area (at first at least) and
so the usual disk check facilities off load a section of the disk and then
write to and read back on that section to test.  I lost my Windows disk on
this box I am using a couple of months ago.  A section of the disk was
faulty - major errors when it tried to test that section.  The rest of the
disk seemed to do fine.  At any rate I would check the disk.  Use only
non-destructive testing of course.  It takes a long time with today's
bigger disks. If I recall it took about eight hours to process my modest
160GB disk.

Also, it may well prove worth your time to use Clonezilla to take an image
"snapshot" of the disk at this time.  When my disk did fail a lot of time
was saved by having an image on hand to use on the new disk (actually I had
two identical disks as part of the original box build - identical disks are
very nice with using Clonezilla).  If you end up replacing the disk
basically you will need a same or bit larger disk for Clonezilla to be
happy although I hear that there are options.

Working with Fedora (I am no expert with Fedora) my tendency for doing a
re-install is to use live disk Parted to erase the Fedora partitions (and
swap) and then install from a Fedora live disk.  The installer will see the
free space and gladly use it.  Part of the install process does a fresh
install of Grub 2.  So Grub 2 will see your untouched XP partition and make
a boot menu path to it.


On Sat, Aug 30, 2014 at 9:50 AM, Angelo Moreschini <
mrangelo.fedora at gmail.com> wrote:

> Hi,
>
> I tried to use the "single-user-mode" but I had problem.
> Typing "e" from the interactive menu (to choose the OS) I get the message:
> *[0.000000] tsc: FAST  TSC  CALIBRATION FAILED.*
>
> In the following line I got the prompt, but was not able to type anything
> there (on the screen).
>
> Can be that the actual installation is not good.. ?
> (also I am not able to login as root ... the message that I get is "login
> incorrect").
>
> What do you think that I can do?
>
> Thank you
>
> Angelo
>
>
>
>
> On Sat, Aug 30, 2014 at 11:49 AM, KW <kilowattradio at comcast.net> wrote:
>
>>
>>
>> On 08/30/2014 01:13 AM, Angelo Moreschini wrote:
>> > Hi, after that I installed fedora 20, I am not able to get the
>> > login as su. When I try to sign me as super user, I always get the
>> > answer "Authentication failure".
>> >
>> > I don't think that I really type wrong the password that I set at
>> > install time:/I typed it twice/. Rather I think that they are some
>> > funny characters inside it.
>> >
>> > So I lost the hope to try to guess the password and I think to re
>> > install Fedora.., but I have a problem.
>> >
>> > My computer is dual boot with Windows XP and I am not sure how
>> > uninstall Grub (how to manage the MBR when to the computer start)
>> > before to uninstall Fedora... Some time ago I tried to fix this
>> > problem using Windows in recovery mode (command fixboot) and, at
>> > last, I had to reinstall also Windows XP (further that Fedora)..
>> >
>> > Can I have an advice how  to arrange the dual boot on my computer,
>> > before to uninstall Fedora??
>> >
>> > Thank you regards
>> >
>> > Angelo
>> >
>> >
>> >
>> Hi you do not have to reinstall Fedora to reset the super user or root
>> account password. You need to boot into single user mode then type
>> passwd at the prompt then enter a new password.
>>
>> Here are the instructions for single user mode:
>> <
>> http://docs.fedoraproject.org/en-US/Fedora/13/html/Installation_Guide/s1-rescuemode-booting-single.html
>> >
>>
>>
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