{URGENT} Changed "other" permissions to none for bin, etc and dev and can't access the terminal and root

I changed "other" permissions to none for bin, etc and dev folders as root, and now there is no access to terminal, programs, also no possibility to login in a window as admin. When I was still using the terminal after changing these permissions, shortly before the terminal stopped to be displayed by Ctrl+Alt+T, the format <[email protected]:~$> changed to <I have no [email protected]:~$> and a folder with PCname in home/username directory was created.
I'm using Ubuntu Mate 18.04.1. I didn't shut up the PC for a few days, so a folder var/log/tiger (as superuser) is still opened and I can create files there, but can't copy.

At #ubuntu by support I was advised to boot from a different but compatible file system or Ubuntu Live CD and change the permissions from there. But they said that PC may not also properly boot up, so I'm not shutting it down yet. They also didn't provide an estimate of how likely will it be possible to restore "other" permissions to at least the bin folder if booting up and mounting a compatible file system.
Can you advise on how to handle permissions to bin folder while booting from Live CD?

I wrote an Ubuntu Mate 18.04.3 .iso image to an USB stick (18.04.1 not available for download) and it seems to start ok in active current GUI session, despite that I set "other" permissions to 0 for /dev also.
I thought that as an alternative for booting from a Live CD it would be better to have some "Root restore tool" bootable from an USB stick into active GUI session. As I have another PC with Ubuntu Mate 16.04, there I could write this app onto USB stick to be bootable from USB and enter and save my Ubuntu Mate 18.04 root password into this app. So that after inserting into PC with 0 "other" permissions for bin folder it would access the file system already as root so I could change the permissions in current active GUI session.
Does such tool already exist or is it very difficult to write such script to be root-bootable from USB?

I use PC with Ubuntu Mate 18.04 for work and it is sort of rather disappointing that a proclaimed highly reliable file system architecture is subject to changes in "other" permissions and doesn't maintain uniformity of root operations.

Hi,

you don't log in to Ubuntu as "root", any changes you make to the user are done as root, once you tell the system that the user has no access or only certain privileges, you effectively cripple the system, it is not Ubuntu's fault!.

Do you have separate root and home partitions?, if you do, you can at least recover your data safely if you use the following:

Install Ubuntu (Mate) using "Something else" method :grinning:

I was not making changes to the user by applying chmod, a changed only the "other" section of bin folder. I didn't change anything in root folder, why then it became affected in a way than a non-root can't change into root in GUI windows?
It is an Ubuntu fault to not keep essential root functions closed in one module in root folder and not build bindings of root to default user registered at installation etc. I've got info about permissions that root-related programs are stored in sbin and not in bin.

I suppose I was not mounting home partition separately, I copied it to hdd, but I need to recover browsers' bookmarks from current GUI and from Windows virtual machine, and some files from this VM.

So you mean that either booting from Ubuntu Live CD or from the USB bootable app described above won't provide the possibility to reset the permissions to bin folder?

No, you can certainly use the Live CD, I don't know what the commands would be but you can try finding out by searching from:

https://askubuntu.com/ :grinning: