- Modify File Permissions with chmod(linode.com)
Chmod CHEAT SHEET
This quick reference cheat sheet provides a brief overview of file permissions, and the operation of the chmod command
permission
4
Sections
19
Cards
#Getting Started
Syntax
$ chmod [options] <permissions> <file>
Example
$ chmod 755 foo.txt
$ chmod +x cheatsheets.py
$ chmod u-x cheatsheets.py
$ chmod u=rwx,g=rx,o= cheatsheets.sh
Change files and directories recursively
$ chmod -R 755 my_directory
The chmod command stands for "change mode"
Chmod Generator
Chmod Generator allows you to quickly and visually generate permissions in numerical and symbolic.
Common Permissions
| Command | s | Meaning |
|---|---|---|
400 | r-------- | Readable by owner only |
500 | r-x------ | Avoid Changing |
600 | rw------- | Changeable by user |
644 | rw-r--r-- | Read and change by user |
660 | rw-rw---- | Changeable by user and group |
700 | rwx------ | Only user has full access |
755 | rwxr-xr-x | Only changeable by user |
775 | rwxrwxr-x | Sharing mode for a group |
777 | rwxrwxrwx | Everybody can do everything |
Explains
$ ls -l
-rw-r--r-- 1 root root 3 Jun 29 15:35 a.log
drwxr-xr-x 2 root root 2 Jun 30 18:06 dir
Permission analysis of "dir"
d rwx r-x r-x
β¬ ββ¬β ββ¬β ββ¬β
β β β β
β β β ββ 4. Otherο½5 (4+0+1)
β β βββββββ 3. Groupο½5 (4+0+1)
β ββββββββββββ 2. User ο½7 (4+2+1)
ββββββββββββββββ 1. File Type | directory
Permission Modes
| Permission | Description | Octal | Decimal |
|---|---|---|---|
--- | No Permission | 000 | 0 (0+0+0) |
--x | Execute | 001 | 1 (0+0+1) |
-w- | Write | 010 | 2 (0+2+0) |
-wx | Execute and Write | 011 | 3 (0+2+1) |
r-- | Read | 100 | 4 (4+0+0) |
r-x | Read and Execute | 101 | 5 (4+0+1) |
rw- | Read and Write | 110 | 6 (4+2+0) |
rwx | Read, Write and Execute | 111 | 7 (4+2+1) |
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Objects
| Who (abbr.) | Meaning |
|---|---|
u | User |
g | Group |
o | Others |
a | All, same as ugo |
{.show-header}
Permissions
| Abbreviation | Permission | Value |
|---|---|---|
r | Read | 4 |
w | Write | 2 |
x | Execute | 1 |
- | No permission | 0 |
{.show-header}
File Types
| Abbreviation | File Type |
|---|---|
d | Directory |
- | Regular file |
l | Symbolic Link |
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#Chmod Examples
Operators
| Symbol | Description |
|---|---|
+ | Add |
- | Remove |
= | Set |
chmod 600
$ chmod 600 example.txt
$ chmod u=rw,g=,o= example.txt
$ chmod a+rwx,u-x,g-rwx,o-rwx example.txt
chmod 664
$ chmod 664 example.txt
$ chmod u=rw,g=rw,o=r example.txt
$ chmod a+rwx,u-x,g-x,o-wx example.txt
chmod 777
$ chmod 777 example.txt
$ chmod u=rwx,g=rwx,o=rwx example.txt
$ chmod a=rwx example.txt
Symbolic mode
Deny execute permission to everyone.
$ chmod a-x chmodExampleFile.txt
Allow read permission to everyone.
$ chmod a+r chmodExampleFile.txt
Make a file readable and writable by the group and others.
$ chmod go+rw chmodExampleFile.txt
Make a shell script executable by the user/owner.
$ chmod u+x chmodExampleScript.sh
Allow everyone to read, write, and execute the file and turn on the set group-ID.
$ chmod =rwx,g+s chmodExampleScript.sh
Removing Permissions
In order to remove read write permissions given to a file, use the following syntax:
$ chmod o-rw example.txt
For our file example.txt, we can remove read write permissions using chmod for group by running the following command:
$ chmod g-rx example.txt
To remove chmod read write permissions from the group while adding read write permission to public/others, we can use the following command:
$ chmod g-rx, o+rx example.txt
But, if you wish to remove all permissions for group and others, you can do so using the go= instead:
$ chmod go= example.txt
Executable
$ chmod +x ~/example.py
$ chmod u+x ~/example.py
$ chmod a+x ~/example.py
chmod 754
$ chmod 754 foo.sh
$ chmod u=rwx,g=rx,o=r foo.sh
#Chmod Practices
SSH Permissions
$ chmod 700 ~/.ssh
$ chmod 600 ~/.ssh/authorized_keys
$ chmod 600 ~/.ssh/id_rsa
$ chmod 600 ~/.ssh/id_rsa.pub
$ chmod 400 /path/to/access_key.pem
Web Permissions
$ chmod -R 644 /var/www/html/
$ chmod 644 .htaccess
$ chmod 644 robots.txt
$ chmod 755 /var/www/uploads/
$ find /var/www/html -type d -exec chmod 755 {} \;
Batch Change
$ chmod -R 644 /your_path
$ find /path -type d -exec chmod 755 {} \;
$ find /path -type f -exec chmod 644 {} \;
See: Command Substitution