Linux File Permissions and Commands

Vocabulary flashcards covering Linux file permissions, owner types, ls options, and chmod argument modifiers.

Read permission (for files)

The ability to read the file contents.

Read permission (for directories)

The ability to read all contents in the directory including both files and subdirectories.

Write permission (for files)

The ability to make modifications on the file contents.

Write permission (for directories)

The ability to create new files in the directory.

Execute permission (for files)

The ability to execute the file if it is a program.

Execute permission (for directories)

The ability to enter the directory and access its files.

User (owner type)

The owner of the file.

Group (owner type)

A larger group that the owner is a part of.

Other (owner type)

All other users on the system.

1st character (Linux permission string)

Indicates file type: d for directory, - for a regular file.

2nd character (Linux permission string)

Indicates read permissions for the user (r if user has read permissions, - if lacking).

3rd character (Linux permission string)

Indicates write permissions for the user (w if user has write permissions, - if lacking).

4th character (Linux permission string)

Indicates execute permissions for the user (x if user has execute permissions, - if lacking).

5th character (Linux permission string)

Indicates read permissions for the group (r if group has read permissions, - if lacking).

6th character (Linux permission string)

Indicates write permissions for the group (w if group has write permissions, - if lacking).

7th character (Linux permission string)

Indicates execute permissions for the group (x if group has execute permissions, - if lacking).

8th character (Linux permission string)

Indicates read permissions for other (r if other owner type has read permissions, - if lacking).

9th character (Linux permission string)

Indicates write permissions for other (w if other owner type has write permissions, - if lacking).

10th character (Linux permission string)

Indicates execute permissions for other (x if other owner type has execute permissions, - if lacking).

ls -a

Displays hidden files, which start with a period (.) at the beginning.

ls -l

Displays permissions to files and directories, owner name, group, file size, and the time of last modification.

ls -la

Displays permissions to files and directories, including hidden files (combination of -a and -l options).

Principle of least privilege

The concept of granting only the minimal access and authorization required to complete a task or function.

chmod command

Changes permissions on files and directories.

u (chmod modifier)

Indicates changes will be made to user permissions.

g (chmod modifier)

Indicates changes will be made to group permissions.

o (chmod modifier)

Indicates changes will be made to other permissions.

• (chmod modifier)

Adds permissions to the user, group, or other.

• (chmod modifier)

Removes permissions from the user, group, or other.

= (chmod modifier)

Assigns permissions for the user, group, or other, setting them exactly as specified and overwriting existing permissions.