[linux master][리눅스 마스터][국가기술자격]  How to fix sudo after "chmod -R 777 /usr/bin"?   

/usr/bin/sudo must be owned by uid 0 and have the setuid bit set

I entered chmod -R 777 /usr/bin and now sudo is not working.

It says sudo must be setuid root.

Some advice online said to run chown root:root /usr/bin/sudo chmod 4755 /usr/bin/sudo.

On entering chown root:root /usr/bin/sudo it shows an opened in readonly mode error.

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I couldn't be a root user by using the "su" command because I didn't have a root password, but instead I used this command to become a root user: systemd-run --shell and after that: chown root:root /usr/bin/sudo && chmod 4755 /usr/bin/sudo My problem is solved.

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On an Ubuntu desktop system, PolicyKit is installed, so pkexec can be used to repair a broken sudo executable or sudoers file. You do not need to boot into recovery mode and you do not need to boot from a live CD. You don't even need to reboot.

In this case, run the following commands:

pkexec chown root:root /usr/bin/sudo
pkexec chmod 4755 /usr/bin/sudo

[출처1] https://askubuntu.com/questions/127446/how-to-fix-sudo-after-chmod-r-777-usr-bin

[출처2] https://repost.aws/ko/questions/QUCmOj_ncRRkayvV29-KmaTg/i-get-this-error-trying-to-run-sudo-command-sudo-usr-bin-sudo-must-be-owned-by-uid-0-and-have-the-setuid-bit-set?sc_ichannel=ha&sc_ilang=en&sc_isite=repost&sc_iplace=hp&sc_icontent=QUCmOj_ncRRkayvV29-KmaTg&sc_ipos=15