1.6 SUID / GUID
Suid means that if a user sets this permissions to belong to its own shell script, then other users will have the corresponding permissions of the owner when performing this script. The same principle also applies to the GUID, and the user who performs the corresponding script will have the user's permissions in the user group belonging.
1.6.1 How to set SUID / Guid
Enter / bin or / sbin directory, execute:
$ ls -l | grep '^ ... s'
The above command is used to find Suid files
$ ls -l | grep '^ ... s ... s
The above command is used to find SUID and GUID files
To set the SUID, set the one before the corresponding permission bit is set to 4; if you want to set the GUID, then set the one before the corresponding permission bit is set to 2; two bits are set, 4 2.
Once this bit is set, a S will appear in the X position. To set up Suid / GUID, you must open the execution permission.
You can also use a symbolic manner to set Suid / GUID.
Note: The chmod command does not perform the necessary integrity checks, you can give any privileges for a file that is useless, but nothing to do for the set permissions.
1.7 Chown and ChGRP
Used to change the owner of the file, but only the owner and system administrator of the file can operate, formatted:
Chown -r -h Owner File
-R means that the files in all word directory are also available
-h means that the target file points to the link pointing to the link when changing the symbolic link file owner
1.7.1 Chown Example
$ Chown LP Project
Give the ownership of the file Project from the original file owner to the user LP
1.7.2 chgrp
The format of CHGRP and the format of Chny are similar, and ChGRP changes the group belonging.
1.7.3 find out the user group you belong to
$ GROUP or $ ID
1.7.4 Find the group to which other users belong
$ group username
1.8 umask
Umask determines the default mode when you create a file. The umask command is set in / etc / profile. If you want to modify the value of umask, put it in your .profile or .bash_profile file in your $ home directory.
1.8.1 How to calculate uMask values
Like the umask and chmod commands, use absolute mode settings, but note that the system does not allow you to give it permission when you create a text file, you must add this permission after you create CHMOD. The directory allows you to set the execution permission.
1.8.2 Common UMASK value
Umask value directory file
022 755 644
027 750 640
002 775 664
006 771 660
007 770 660
Query the current umask value
$ umask
Modify the current UMASK value
$ umask value
1.9 symbolic link
There are two different types of links, soft links, and hard links. Only the soft link is discussed, which is a pointer to a file.
1.9.1 Use soft links to save files
LN [-s] source_path target_path where the path can be a directory or a file.
