PART 2: checking how to reset sudo and root password on Ubuntu 21.04

[M. Fioretti]

Hello all, with many thanks to everybody who already answered, and
some much needed clarification/extra info from my side:

First, of course I will reinstall asap, that was the plan since the
beginning. Trouble is, as I said, that computer just came back in my
hands, without an adequate "latest backup". That (and some other
checks/restorations) is exactly what I had not finished doing when I
did that big mistake of, as Ralf said "run chown recursively in the
root directory".

Second, I mentioned I have no decent bandwidth for the near future to
download 22.04 LTS, that is why I would really to patch this box, just
the bare minimum needed to finish those backups and checks, copy what
needs copying on external drive and nothing else. Once that is over, I
can even wait a week to download and install the new OS

Third, surely the effects of an error like are many, and could take
years to discover. But AFAICT everything works fine, except a couple
of shell scripts that I *absolutely** need to run to find certain
files, remove duplicates, stuff like that. Indeed, I realized what a
mess I had made just when running those scripts, that use "find" and
"md5sum" that (IIRC, not 1000000% sure of the exact sequence anymore):

the script failed to check some directories because of permissions

I thought OK, let's do "chown -R" since those are only user files to find
and backup

but I did chown -r in the wrong place

so when I run the script again, even with sudo, it failed because I
had messed up the permission in /etc:

sudo: /etc/sudo.conf is owned by uid 755, should be 0
sudo: /etc/sudo.conf is owned by uid 755, should be 0
sudo: /etc/sudoers is owned by uid 755, should be 0
sudo: no valid sudoers sources found, quitting
sudo: error initializing audit plugin sudoers_audit

So, summing up this and your advice, IIUC:

1) all I must really do here is only to chown -R root:root inside /etc
and nothing else, just so that sudo works again and I can run those
scripts of mine to clean and back up user files before reinstalling

2) then, having no broadband for the moment, the quickest, least worst
way to go is to boot in single user mode, that is follow the exact procedure here:
https://www.osradar.com/access-single-user-mode-ubuntu-20-04/

BUT, instead of changing root password, just run chown -R root:root
/etc

so I could do all the maintenance before reinstalling & back up. Thend
then, since / and /home are on separate partitions, when I finally get
to reinstall, I would leave the cleaned /home untouched, without
copying back all the files.

Is this correct? does it make sense?

Thanks,
Marco



On Fri, Oct 14, 2022 15:13:29 PM -0500, Aaron Rainbolt wrote:
> On Fri, Oct 14, 2022 at 12:43 PM Marco Fioretti <mfioretti at nexaima.net> wrote:
> >
> > Greetings,
> >
> > I recently recovered an Ubuntu 21.04 box I had set up back then, and then "leased" to a relative.
> > I will upgrade it asap to 22.04 LTS, BUT, for reasons not relevant here, while doing backups and
> > generally "cleaning up" that box:
> >
> > 1) I made a mistake, issuing a chown command in /, thus messing up, among other things,
> >     ownership of critical files in /etc/, so now sudo does not work anymore
> 
> Ouch. There isn't really a good way to fix this with 100% accuracy
> that I know of. A reinstall will be needed. However, you'll probably
> be able to back it up without needing to boot into a live USB.
> 
> > 2) AND I forgot the root password, so I cannot just "su" and fix those ownerships manually
> >
> > 3) but again, I have to fix those ownerships and other stuff, and back up before upgrading.
> 
> I'd boot into recovery mode at this point. If you're on a BIOS system,
> press and hold Shift during early boot until you get a GRUB screen. On
> EFI systems, press Esc at just the right moment during early boot
> (might be tricky to find the exact spot to do this at). When the GRUB
> menu pops up, select "Advanced Option for Ubuntu", then select the
> second entry (it should say "(recovery mode)" in it). You use the
> arrow keys to move around and the Enter key to select an opion.
> 
> Once you're booted into recovery mode, select the "root" option to
> drop to a shell, then run "mount -o remount,rw /" to gain write access
> to the root drive. At this point, you can plug in an external drive,
> find the external drive with lsblk, mount it to /mnt, and then use cp
> or rsync to copy your important data to the external drive.
> 
> > I know I could boot a live distro and work from there but I have very slow connectivity right now,
> > AND I want to refresh my skills for these situations  anyway, just to have more alternatives.
> >
> > So, since I CANNOT risk to mess up that box even more, I would really appreciate a confirmation
> > that the root password reset procedure described here:
> >
> > https://unixcop.com/how-to-reset-root-password-on-ubuntu-21-04/
> >
> > is 10% complete and correct for Ubuntu 21.04, and if there are better ways to reset a root password at the prompt, without using
> > a live distro.
> 
> No need to do any root password reset or anything. Just back up your
> data and reinstall the whole OS from scratch. You won't be able to
> easily fix a permissions issue like this. Sorry that you're stuck in
> this mess, and good luck! We're here to help if something is still
> tricky to work with.
> 
> > TIA,
> > Marco
> >
> >
> >
> >
> 

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