After a power cut my machine cannot boot

[Sam Varshavchik]

Paul Smith writes:

> On Wed, Sep 9, 2015 at 7:26 PM, Joe Zeff <joe at zeff.us> wrote:
> >>
> >> on a F21 machine, there occured a power cut. And now I cannot boot the
> >> machine, and when I use the rescue mode and try to run again
> >>
> >> yum update
> >
> >
> > I know I'm coming in late, and judging from other replies this probably
> > won't work, but have you tried yum-complete-transaction?  I'd suggest using
> > --skip-broken, but that only checks for certain errors in the files rather
> > than doing what the name implies.
> >
> > Going off-topic for a moment, and presuming that dnf acts the same way (I
> > don't, as yet, have a box using it.) should there be a bugzilla either
> > complaining that the switch doesn't actually do what it says (e.g.,  
> skipping
> > to the next package if this one is broken instead of only being able to  
> pull
> > it out of the transaction if the signature (I think it is.) doesn't match.)
> > or requesting that it be renamed to something more appropriate, with the
> > current switch being left as an alias for the correct one to keep scripts
> > from breaking.  I'm neutral on the subject, although I'd prefer that
> > something be done to keep people from wasting time trying in cases where it
> > doesn't apply.
>
> Thanks, Joe. I have just tried
>
> yum-complete-transaction
>
> but with no success: the error message ("/lib64/libidn.so.11: file too  
> short").

This is a critical system library. It has been hopelessly corrupted. You  
cannot run anything. libidn.so.11 is a critical system library, used  
probably by 99% of binaries on an average system. Any command someone will  
suggest for you try won't work, because the command itself needs libidn.so. 
11, and it's broken.

If you have another working system, it should be possible to recover this  
library using a rescue disk; by first fscking the filesystem to get it into a  
consistent state, and then meticulously restoring the corrupted files from  
another good system.

However, this procedure does require a fairly good amount of technical  
experience and knowledge. Furthermore, all you know is that libidn.so is  
corrupted. You have absolutely no guarantees, whatsoever, that this is the  
only corrupted system library. After fixing it, it's fairly likely that you  
will discover that another critical system library is similarly corrupted. I  
can pretty much guarantee you that this is the case.

Eventually, you will get to the point where you apparently restored all the  
critical files, and you are seemly able to boot, but probably won't be able  
to boot all the way through to the desktop, due to some less-critical  
libraries being similarly corrupted, or other kinds of critical files  
missing, but that doesn't come up until a later point in the boot process,  
and the error message is lost somewhere that's not easy to find. All you  
know that that the boot hangs, with no immediate indication as to what's  
broken.

I'm just giving you the most likely scenario I think you will end up with,  
if you try to continue along the path of trying to salvage this system.  
Based on what you already wrote in this thread, I think the best thing for  
you to do is to simply reformat and reinstall. Using a rescue disk, it  
should be possible for you to salvage any individual files you need off this  
system, before reinstalling it, if necessary.

And once you have everything reinstalled, invest in a good UPS so you won't  
have to do this again.

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