Linux Learning Notes (8)

One, file or directory permissions chmod

rw-r--r--。

——— ——— ——— ——

Owner-owned group others are subject to selinux restrictions

R readable =4 w writable =2 x executable =1

chmod + number + file name modification permissions

All sub-files and subdirectories in the-R directory are batch modified permissions

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chmod + u/g/o + file name modification permissions

A = Ugo a-x all permissions minus Execute permission

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There are two ways to remove the selinux limit.

1, temporarily close SELinux

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2, permanent, modify SELinux configuration file

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Ii. Change owner and owning group Chown

Chown Change Owner

Chown + users: Group + files change users and owning groups at once

CHGRP Change group changes all groups

Chown-r Batch change owner or group of all files under directory

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Third, Umask

Umask Determining default File directory permissions

Root umask Default Value 0022

The directory and the file are different. Directory must have X permissions, access to the directory is the execution directory, so there must be X permissions

So directory

777 Minus Umask

The file is made up of

666 minus Umask

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Exception: When Umask is 003, the file directory is 664

666-003 = (rw-rw-rw-)-(-------wx) = rw-rw-r--= 664

777-003 = (rwxrwxrwx)-(---------wx) =rwxrwxr--= 774

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Four, hidden permissions lsattr_chattr

Chattr change file attributes on a Linux file system

Chattr Set hidden Permissions command

+i changing files to read-only files, cannot be changed, cannot be deleted, cannot be renamed

For directories, cannot be deleted, cannot create new files, cannot be renamed, but cannot restrict writing of existing sub-file contents

-I cancel I permissions

(vi command to change a file, will save a cache file, such as Modify 1.txt, the 1.txt~ file will appear, when the Wq save exit, will overwrite the original file.

After you set the Hide permissions I, the file cannot be saved and a 1.txt~ cache file is automatically generated. ）

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+a can only append to a file and change the time information (touch). Cannot be deleted, cannot be changed. cannot be renamed. such as logs,

You can add sub-files to a directory, or you can change the contents of a child file.

-A Cancel a permission

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Lsattr View hidden Permissions command to view the file itself or subdirectories and sub-files under the directory

-R view hidden permissions for files under directories and subdirectories

-A even hidden file hidden permissions also view

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Linux Learning Notes (8)