PetexSpace

Chmod Cheatsheet

This quick reference cheat sheet provides a brief overview of file permissions, and the operation of the chmod command

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

Owner
Group
Others
755-rwxr-xr-x

Chmod Generator allows you to quickly and visually generate permissions in numerical and symbolic.

Common Permissions

CommandsMeaning
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
┬  ─┬─  ─┬─  ─┬─
│   │    │    │
│   │    │    └─ 4. Other｜5 (4+0+1)
│   │    └────── 3. Group｜5 (4+0+1)
│   └─────────── 2. User ｜7 (4+2+1)
└─────────────── 1. File Type | directory

Permission Modes

PermissionDescriptionOctalDecimal
---
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)

Objects

Who (abbr.)Meaning
u
User
g
Group
o
Others
a
All, same as ugo

Permissions

AbbreviationPermissionValue
r
Read
4
w
Write
2
x
Execute
1
-
No permission
0

File Types

AbbreviationFile Type
d
Directory
-
Regular file
l
Symbolic Link

Chmod Examples

Operators

SymbolDescription
+
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

Also see

Adapted from Fechin/referenceGPL-3.0 licenseMarkdown sourceChanges and attribution