Settings for Linux file and directory permissions

Linuxsettings for file and directory permissionsModify File Permissions

If you want to change the permissions of a file or directory, you can use the chmod command to change the permissions of a file or directory in two ways: mnemonic and octal.

• Mnemonic Method:

Grammar:

use u (user) g (group) o (Other) Span style= "font-family: ' The song Body '; >, a (All) Span style= "FONT-FAMILY:CALIBRI;" >+ - = means what permissions are set, using rwx represents permissions.

For example:

[email protected] tmp]# Touch test.txt

[email protected] tmp]# LL

Total 0

-rw-r--r--1 root root 0 Jul 8 19:51 test.txt

[Email protected] tmp]# chmod u+x test.txt

[email protected] tmp]# LL

Total 0

-rwxr--r--1 root root 0 Jul 8 19:51 test.txt

[Email protected] tmp]# chmod go-r test.txt

[email protected] tmp]# LL

Total 0

-rwx------1 root root 0 Jul 8 19:51 test.txt

# chmod u=rw-,go=r--test.txt

[email protected] tmp]# LL

Total 0

-rw-r--r--1 root root 0 Jul 8 19:51 test.txt

[Email protected] tmp]# chmod a=---test.txt

[email protected] tmp]# LL

Total 0

----------1 root root 0 Jul 8 19:51 test.txt

• Eight binary

Grammar:

convert chmod letters to octal filenames

Modify the owner of a file

Change the owner of the file, using the chown command

Syntax 1:

Chown [-r] User file

Example: Modifying the test.txt master to u100

[Email protected] tmp]# chown u100 test.txt

[email protected] tmp]# LL

Total 0

-rw-r--r--1 u100 Root 0 Jul 8 13:59 test.txt

Syntax 2:

Chown [-r] User.group file

Cases:

# chown U101.u100 A

2.3 Modifying the genus Group of a file

Change the genus group using the chgrp command

Grammar:

Chgrp GROUP FILE

Example: Modifying the genus Test.txt to u100

# chgrp U100 test.txt

[email protected] tmp]# LL

Total 0

-rw-r--r--1 u100 u100 0 Jul 8 13:59 test.txt

Controlling default Permissionsumask

The new file or directory has a default permission, which is changed by the standard concept of umask. In the system, each process, including the shell, uses a three-digit octal number to "cloak" the permissions of the newly created file or directory, and the octal number is called umask.

• Default permissions for files

Kernel 666 666

Umask 022 077

644 600

• Default permissions for directories

Kernel 777

Umask 022

755

• Querying the system for umask values

#umask

0022

• Modify umask

#umask 077

Special permissions

• Modify SUID:

#chmod u+s filename or chmod 4755 filename

• Modify SGID

#chmod g+s filename or chmod 2755 filename

• Sticky bits

# chmod o+s filename or chmod 1755 filename

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