Directive Name: chmod
Use Rights: All users
How to use: chmod [-CFVR] [--help] [--version] Mode file ...
Description: Linux/unix file access rights are divided into three levels: file owners, groups, others. Using chmod can
To control how the file is accessed by others.
Mode: Permission set string, the format is as follows: [Ugoa ...] [[+-=][RWXX] ...] [,...], where u represents the possession of the file
, g means that the owner of the file belongs to the same group (group), O to other people, a means that all three
Is.
+ means to increase permissions,-to indicate cancellation rights, = to represent a unique set of permissions.
R means readable, W is writable, X is executable, x means only if the file is a subdirectory or the file has been
Set over to executable.
-C: Display the change action if the file permissions have actually changed
-F: Do not display error messages if the file permissions cannot be changed
-V: Show details of permission changes
-r: The same permission changes are made to all files under the current directory and subdirectories (that is, to be changed one at a time)
--HELP: Show Auxiliary Instructions
--version: Display version
Example: Set the file file1.txt to be readable by all people:
chmod ugo+r File1.txt
Set the file file1.txt to be readable by all people:
chmod a+r File1.txt
The file file1.txt and File2.txt are set as the owner of the file and are writable by the same group as which they belong, but other than the
Person is not writable:
chmod ug+w,o-w file1.txt File2.txt
Set ex1.py as only the owner of the file can perform:
chmod u+x ex1.py
All files and subdirectories under the current directory are set to anyone can read:
Chmod-r A+r *
In addition chmod can also use numbers to indicate permissions such as chmod 777 file
Syntax is: chmod ABC file
Each of these a,b,c is a number, representing the permissions of user, Group, and other respectively.
R=4,w=2,x=1
To rwx the property is 4+2+1=7;
To rw-the property is 4+2=6;
To r-x the property is 4+1=7.
Example:
chmod a=rwx File
And
chmod 777 File
Same effect
chmod ug=rwx,o=x File
And
chmod 771 File
Same effect
If you use chmod 4755 filename, you can make this program have root permissions
directive Name: Chown
Use Rights: Root
Use mode: Chown [-CFHVR] [--help] [--version] user[:group] File ...
Description: Linux/unix is a multiple-person work system, all files are owned by the owner. Using Chown, you can use the file to hold
There are those who change. Generally speaking, this instruction is only used by System Manager (Root), the general user does not have permission to
To change someone else's file owner, there is no authority to change the file owner to someone else. Only System Manager (Root)
have such permissions.
User: New file owner user idgroup: New file owner user Group-C: if the file
The owner has indeed changed to display its change action-F: Do not display error messages if the file owner cannot be changed------H:
Change only for link (link), not the file that link actually points to----V: Displays details of owner changes-R: to the Eye
All files in the previous directory are subject to the same owner changes as subdirectories (that is, changing recursively)--help: Show Auxiliary
Description--version: Display version
Example:
To set the owner of the file file1.txt as the user of the Users group Jessie:
Chown Jessie:users File1.txt
All files and subdirectories under the current directory are set up as users of the Users group Lamport:
Chown-r Lamport:users *
-RW-------(600)--only the owner has read and write access.
-rw-r--r--(644)--only the owner has read and write access, while the group users and other users have access only.
-RWX------(700)--only the owner has the right to read, write and execute.
-rwxr-xr-x (755)--the owner has the right to read, write, execute, and the group of users and other users only read, execute permissions.
-rwx--x--x (711)-The owner has the right to read, write, execute, and the group of users and other users only execute permissions.
-rw-rw-rw-(666)-All users have file read and write permissions. This practice is not advisable.
-RWXRWXRWX (777)-All users have read, write, execute permissions. More undesirable approach.
The following are two common settings for a directory:
DRWX------(700)-only the owner can read and write in the directory.
Drwxr-xr-x (755)-All users can read the directory, but only owners can change the contents of the catalog
SUID's representative number is 4, like 4755, the result is-rwsr-xr-x.
Sgid's representative number is 2, like 6755, the result is-rwsr-sr-x.
Sticky Digit is 1, for example, 7755 is the result of-rwsr-sr-t
(Of course 7755 this chmod setting doesn't make much sense, here's just a demo)
Chown command
Use
Change the owner or group associated with the file.
Grammar
Chown[-F] [-h] [-R] Owner [: Group] {File ... | Directory ...}
Chown-r[-F] [-h|-l|-P] Owner [: Group] {File ... | Directory ...}
Describe
The chown command changes the owner of the file specified by the files parameter to the user specified by the owner parameter. The value of the Owner parameter can be a user identity or a login name that can be found in the/etc/passwd file. You can also optionally specify a group. The value of the group parameter can be the group identity or group name that can be found in the/etc/group file.
Only the root user can change the owner of the file. You can change the group of files only if you are root or if you own the file. If you own a file but are not a root user, you can only change the group to a group for which you are a member.
Although the-H,-l, and-p flags are mutually exclusive, specifying more than one is not considered an error. The last flag specified determines the operation that the command draft will demonstrate.
Sign
-F
Disables all error messages except the usage message.
-H
Change ownership of the symbolic link that is encountered, rather than the ownership of the file or directory to which the symbolic link points.
When you encounter a symbolic link and you do not specify the-H flag, the Chown command changes the ownership of the file or directory that the link points to, not the link itself.
If you specify the-r flag, the Chown command recursively descending the specified directory.
-H
If the-r option is specified and the symbolic link of the file referencing the type directory is specified on the command line, the chown variable changes the user identity (and group identity, if specified) of the directory referenced by the symbol, and all files in the file hierarchy under that directory.
-L
If the-r option is specified, and the symbol for a file referencing a type directory is specified on the command line or during traversal of a file hierarchy, the chown command changes the user identity (and group identity, if specified) of the directory referenced by the symbolic link, and all files in the file hierarchy under that directory.
-P
If the-r option is specified and the symbolic link is specified on the command line or encountered during traversal of the file hierarchy, if the system supports the operation, the chown command changes the owner identity (and group identity, if specified) for the symbolic link. The Chown command does not perform symbolic links to any other part of the file hierarchy.
-R
Recursively descending directory to change ownership of each file. When a symbolic link is encountered and the link points to a directory, change the ownership of the directory without further traversing the directory. However, if the-H,-H,-l OR-P flags are not specified, the group ownership of the directory changes without further traversing the directory when the symbolic link is encountered and the link is pointed to the directory.
Security
Access control: This program should be installed as a normal user program in the trusted computing base.
Exit status
This command returns the following export values:
0
The command was executed successfully and all requested changes have been performed.
>0
An error has occurred.
Example
To change the owner of a file program.c:
Chown Jim Program.c
PROGRAM.C's user access rights are now applied to Jim. As the owner, Jim can use
chmod
command allows or denies other users access to PROGRAM.C.
To change the owner and group of all files in the directory/tmp/src to the user John and group build:
Chown-r JOHN:BUILD/TMP/SRC
File
/usr/bin/chown
Chown command
/etc/group
Files that contain group identities
/etc/passwd
Files that contain user identities |
