Cheatsheet: Difference between revisions

;Linux File Permission Basics

* The first character represents the type of file.

* The remaining nine bits in groups of three represent the permissions for the user, group, and global respectively.

File Type User Group Global

d Directory rwx r-x r-x

* Targeted Users:

Who (Letter) Meaning

u user

g group

o others

a all

*Permissions Table:

;chmod Command Syntax and Options

chmod [who][+,-,=][permissions] filename

*Example:

chmod g+w ~/group-project.txt

* The + operator grants permissions whereas the - operator takes away permissions.

* Copying permissions is also possible:

chmod g=u ~/group-project.txt

* The parameter g=u means grant group permissions to be same as the user’s.

* Multiple permissions can be specified by separating them with a comma, as in the following example:

chmod g+w,o-rw,a+x ~/group-project-files/

* Owner of the file is referred to as the user (e.g. u+x).

* The -R option applies the modification to the permissions recursively to the directory specified:

chmod -R +w,g=rw,o-rw, ~/group-project-files/

;Octal Notation for File Permissions:

* The permissions to be set for file:

chmod u=rwx,g=rx,o= group-project.txt

chmod 750 group-project.txt

* Disregarding the first bit, each bit that is occupied with a - can be replaced with a 0 while r, w, or x is represented by a 1:

111 101 000

- rwx r-x ---

* This is called octal notation because the binary numbers are converted to base-8 by using the digits 0 to 7

* Typical default permission: 744

Allows R,W,X permissions for the owner

R permissions for the group and “world” users