1.chmod changes the permissions of the file, only the owner or root user can use it
chmod {n,g,o,a} {+,-,=}{r,x,w} filename or directory
{n,g,o,a} : n : other users g: group o: owner a: everyone
{+,=,- } +:Add permission -:Remove permission =:Modify permission to
chmod 421 filename
r=4 w=2 x=1 For example, chmod 777 fileName changes the file permissions to wrxwrxwrx
-R Modify the permissions of the files in the folder, that is, the folder (recursive modification)
Permission description:
file (file)
r: readable, command cat less more head tail
w: writable vi vim
x: executable script file, command.
dir (folder)
r: can list the file directory ls
w: delete the directory, create a file touch, mkdir, rm
x: can enter the folder cd is generally synchronized with r
2. Change user owner (root only)
chown [user] [file or directory]
3. Change all groups of the file
chgrp [group name] [file or directory]
4. umask -s displays the default permissions for new files
umask 0022
Default permissions are 755
Logical AND of Method 777
777
022
------------
755