Linux Permissions

LINUX USERS, GROUPS & PERMISSIONS Eli the Computer Guy https://www.youtube.com/watch?v=zRw0SKaXSfI ADD USERS sudo adduser <username> prompts will be given, for fleshing out profile DELETE USERS sudo userdel <username> USER PROFILE INFO - TEXT FILE file location:  /etc/passwd VIEW USERS ON LINUX sudo vim [or whatever text editor] /etc/passwd example other text editor: mousepad therefore variation of command:  sudo mousepad /etc/password CHANGE USER'S PASSWORD sudo passwd <username> prompt will guide CONFIGURATION FILES CONTAINING USER INFO         = CONTAINED IN TEXT FILE FORMAT /etc/passwd THREE DIGIT NUMBERS INDICATE PERMISSIONS Example: User, Group, Others 7, 7, 7 7 = full control  (security risk, save for User - versus Group, Others) READ PERMISSION = 4 WRITE PERMISSION = 2 EXECUTE = 1 php files are scripts to work they have to be executed (everyone needs at least a 1 permission to execute scripts on your website) (permission to write is out for Others (website visitors)) eg.  website / web-server = min. 5 for 'Others' (ie read / execute) eg.  full permissions = 7  | read-write permissions = 6 example:  7, 7, 5 permit read           4 deny write             0 permit execute     1   ...   equals:  5 (minimum) sudo chmod <number permissions, eg. 7, 7, 5> <foldername> -R -R = recursive (changes associated / permissions all the way down) example:  sudo chmod 7,7,5 <foldername> -R chmod WITH NUMBERS execute = 1 write = 2 read = 4 PERMISSIONS DEPEND ON INTERNAL SECURITY POLICY eg.   -rw-rw-rwx permissions use the following: Owner                    Group                  Other read & write         read & write        read, write & execute 4+2=6                  4+2=6                 4+2+1=7 equals:  6, 6, 7 TO EXECUTE:  sudo chmod 667 <foldername> Other Example: User                     Group                 Others 4+2+1 = 7           4 + 2 + 0 = 6     0 + 0 + 0 = 0 equals:  7, 6, 0 TO EXECUTE:  sudo chmod 760 <foldername> LIST ALL PERMISSIONS command:  ls -al LIST ALL FILES / FOLDERS  [ in current directory ]   command:  ls -l   permissions for folder shown - eg.  drwxrwxrwx  (completely open, bad security) ('d' represents 'directory' & balance is permissions) (permissions:  Read, Write, eXecute) EXAMPLE: command to change:  sudo chmod 755 <foldername>  -R while in directory that requires change + add permission - remove permission = set permission chown CHANGE OWNER FILES OR FOLDERS USER or GROUP can own file or folder OWNERSHIP CHANGE - USER sudo chown -R <username> <file or folder giving ownership of> Recursive -R for subsequent change to all files & subdirectories (if required) OWNERSHIP CHANGE - GROUP sudo chgrp -R <GroupName> <file or folder giving ownership of>