I've got some problems and to get them fixed, I changed the ownership on /usr from root to user. So many errors thrown afterward, while opening the VBs and basically could not login to root anymore! So the question is that how to get the ownership of /usr back to original, meaning from user's ownership to root ownership. Cause I run sudo -i and I get the operation is not permitted.

Have run the following command before the disaster!
chown -R USER /usr

if i look at my /usr i see owner and group are root:root

so i think the basics are you need to have /usr being owned by user "root" and group "root"

if you change directory to /, it going to be along the lines of:
or if on debian maybe

sudo chown root:root usr -R

basic syntax is :

chown [command] which owner and group do you want to chnage it to root:root -R permission recursive

Which distribution of Linux are you using? Did you have a separate root user which you created a password for or did you use sudo when logged in as your primary user?

Highly unlikely that would resolve whatever problems you had.

It's not that easy, the biggest issue is the suid/sgid bit which gets reset whenever owner is changed. The upshot of this is that even though you restore the owner to root:root, sudo or other commands relying on suid still won't work. Also not all files in /usr are owned by root:root, some are owned by root but have a different group - and this may break programs using these files and running under a non-root account. You are screwed big time. While theoretically there is nothing difficult in restoring corrupted access rights and SCO Unix even had such an utility called fixmog, I don't know of linux equivalent. Reinstall or install the same distro with the same packages, tar /usr, boot from live CD and extract it over your current /usr - tar preserves suid.

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A lot of newbies get caught that way. It's one of the few problems that really need a reinstall. The bonus is that you won't do it again!

The problem is that people coming over from Windows don't immediately understand what file ownership and protections are for. They just seem like a nuisance, getting in the way of something you want to do, so changing them seems like a good solution. As lvm has pointed out, they are baked into the core of all Unix operating systems and should not be altered unless you know exactly what the consequences will be. If you need to manipulate those files, do it as root.

If this is an RPM-based distribution, try as root
This will restore owner, group, permissions and capabilities of all files installed via package management system to the states they were in at the installation time.

For a DEB-based system, you may try something like

As you mentioned It was not that simple. To change back the ownership to root of the directory /usr was unsuccessful.
As I mentioned the operation was not permitted. So I was not even able to login to as a regular user so I had ought to do change thing on boot which I am not that much knowledgeable yet. SO you could guess I lost every info on my system, luckily had backup at some point but all rhcsa's resources for the exam is gone!
I installed Mint again which took me only 10 mins which is worth to skip that painful process of recovery. I got my lesson to not ever again change the ownership of root . That will ruin every program’s structure on my OS.

As you mentioned It was not that simple. To change back the ownership to root of the directory /usr was unsuccessful.
As I mentioned the operation was not permitted. So I was not even able to login to as a regular user so I had ought to do change thing on boot which I am not that much knowledgeable yet. SO you could guess I lost every info on my system, luckily had backup at some point, but all rhcsa's resources for the exam is gone!
I installed Mint again which took me only 10 mins which is worth to skip that painful process of recovery. I got my lesson to not ever again change the ownership of root . That will ruin every program’s structure on OS.

Thats totally true and I understand your point but as a newbie I would expect a warning on changing those critical settings as it not changing simply and ruins everything. I mean I love this OS, I have removed totally windows to focus on linux and its been couple of months I spend at least 5 hrs a day working on this OS but still a typo can ruin everything. I understand the point that it is a professional OS not for everyone but one should starts from somewhere and to be about to screwed like this needs at least a warning in forehand

By the way, I have installed Mint and some other programs again. The original problem was not being able to install guest addition on virtual box and I read some post on oracle website to change the permission on the /Virtualbox directory to get the guest addition run on VB. So changing the ownership on parent directory /usr cause that issue.

But the question remain. The ownership feature of thumb rule which inherits from parent directory to child directory how could it be resolved? Is that only root ownership which should not be touched?

I will save this for next time, since I reinstall Mint again.

How have you tried to install it? Packages virtualbox-guest-utils and virtualbox-guest-x11 should be in Ubuntu repositories Linux Mint uses.

As some User's forum signature says, "Linux assumes the user knows exactly what he/she is doing," as I paraphrase.


Welcome! What you just did is somewhat of an initialization in Linux, as @hazel implies! LOL

An obligatory quote from The UNIX-HATERS Handbook:

An even more dangerous command is
It will treat files and directories in the same way.
Never run it with an absolute 666 or 777!
And it will even follow symbolic links.
Much safer is
One run for files and one for directories.
And none for symbolic links.
Still you must know what you are doing...

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