Linux chmod chown permissions table

user@PC:~$ sudo su

[sudo] password for user:

root@PC:/home/user#

Permission	Command Examples	Description
rwx rwx rwx	chmod 777 filename chmod -R 777 dir	Anybody can read, write, execute.
rwx rwx r-x	chmod 775 filename chmod -R 775 dir	Owner & Group can read, write, execute. Everyone else can read, execute.
rwx rwx r–	chmod 774 filename chmod -R 774 dir	Owner & Group can read, write, execute. Everyone else can read.
rwx r-x r-x	chmod 755 filename chmod -R 755 dir	Owner can read, write, execute. Everyone else can read, execute.
rwx — —	chmod 700 filename chmod -R 700 dir	Owner can read, write, execute. No one else has any rights.
rw- rw- rw-	chmod 666 filename chmod -R 666 dir	Everyone can read, write.
rw- rw- r–	chmod 664 filename chmod -R 664 dir	Owner & Group can read, write. Everyone else can read.
rw- r– r–	chmod 644 filename chmod -R 644 dir	Owner can read, write. Everyone else can read.

root@PC:/home/user# exit

exit

user@PC:~$

Running chmod -R 777 / as root will break your system.

https://www.linode.com/docs/guides/modify-file-permissions-with-chmod/

sudo find / /boot -xdev ! -type s -printf 'chmod %m %p\n' -printf 'chown %u:%g %p\n'

Complete list of default GNU/Linux file permissions as found in Ubuntu Server 16.10 Yakkety Yak with all roles => https://www.vidarholen.net/contents/junk/ubuntu_permissions.html

How to restore root directory permission to default? https://askubuntu.com/questions/958141/fix-permissions-of-server-after-accidental-chmod

sudo adduser user group

sudo deluser user group

groupadd [OPTIONS] GROUPNAME

groupdel [OPTIONS] GROUPNAME