Ten, modify permissions command

Foreword

How to manage the permissions of a file / directory it?
　File permissions calling Linux / Unix is divided into three levels: file owner, group, others.
chmod rights management for a file or directory, the file or directory permissions are controlled to read (R & lt), write (w), execute (x) 3 kinds thereof represent read-write executables.

Modify Permissions command

chmod modify the file, directory permissions

• chomd　u+x/tmp/testfile
• chomd　755 /tmp/testfile

chown Change the owner, is a group

chgrp can be changed independently is a group, not commonly used

Purview

Competence:
U, i.e. the owner of the file or directory User
g, i.e. belongs to a group of files or directories Group
o, Other addition to the file or directory belongs to the owner or a group, other users belong to this range
a, All i.e. all users including owner, owning group, and other users

Exercise

1 a.txt to the owner of the file given executable permissions

@SC02ZRC4KMD6N ~ % ls -l a.txt
-rw-r--r--  1 user1  staff  14  3 29 14:43 a.txt
user1@SC02ZRC4KMD6N ~ % chmod u+x a.txt
user1@SC02ZRC4KMD6N ~ % ls -l a.txt    
-rwxr--r--  1 user1  staff  14  3 29 14:43 a.txt

2 to reduce the read permission is a group

user1@SC02ZRC4KMD6N ~ % chmod g-r a.txt
user1@SC02ZRC4KMD6N ~ % ls -l a.txt    
-rwx---r--  1 user1  staff  14  3 29 14:43 a.txt

3 to the other user settings only write-only privileges

user1@SC02ZRC4KMD6N ~ % chmod o=w a.txt
user1@SC02ZRC4KMD6N ~ % ls -l a.txt    
-rwx----w-  1 user1  staff  14  3 29 14:43 a.txt

4 read permission to all users increases

user1@SC02ZRC4KMD6N ~ % chmod a+r a.txt
user1@SC02ZRC4KMD6N ~ % ls -l a.txt    
-rwxr--rw-  1 user1  staff  14  3 29 14:43 a.txt

5 write permissions to other users in digital, and is a group of their own as read only

user1@SC02ZRC4KMD6N ~ % chmod 446 a.txt 
user1@SC02ZRC4KMD6N ~ % ls -l a.txt    
-r--r--rw-  1 user1  staff  14  3 29 14:43 a.txt

6 Create a default file permissions umask value is 666 minus

user1@SC02ZRC4KMD6N ~ % touch e.txt
user1@SC02ZRC4KMD6N ~ % ls -l e.txt
-rw-r--r--  1 user1  staff  0  3 29 18:15 e.txt
user1@SC02ZRC4KMD6N ~ % umask
022