File Permissions and Ownership
Understanding File Permissions
File Permissions
In Linux, each file has a set of permissions that determine which users can read, write, or execute the file. These permissions are represented by a series of letters and dashes, such as rwxr-xr-x. The first letter represents the file type, and the remaining letters represent the permissions for the owner, group, and other users.
File Types
There are several different types of files in Linux, including regular files, directories, symbolic links, and device files. The first letter in the file permissions represents the file type. The following table lists the different file types and their corresponding letters:
| File Type | Letter |
|---|---|
| Regular File | - |
| Directory | d |
| Symbolic Link | l |
| Device File | c or b |
File Permissions
There are three different types of permissions in Linux: read, write, and execute. The remaining letters in the file permissions represent the permissions for the owner, group, and other users. The following table lists the different permissions and their corresponding letters:
| Permission | Letter |
|---|---|
| Read | r |
| Write | w |
| Execute | x |
File Ownership
Each file in Linux has an owner and a group. The owner is the user who created the file, and the group is a collection of users who have access to the file. The owner and group are represented by a username and a group name, respectively.
Changing File Permissions
Changing File Permissions
To change the permissions of a file, use the chmod command. The chmod command takes two arguments: the permissions to set and the file to set them on. The following table lists the different permissions and their corresponding letters:
| Permission | Letter |
|---|---|
| Read | r |
| Write | w |
| Execute | x |
The following table lists the different users and their corresponding letters:
| User | Letter |
|---|---|
| Owner | u |
| Group | g |
| Other | o |
| All | a |
The following table lists the different operations and their corresponding letters:
| Operation | Letter |
|---|---|
| Add | + |
| Remove | - |
| Set | = |
The following table lists some examples of how to use the chmod command:
| Command | Description |
|---|---|
chmod u+x filename | Add execute permission for the owner of the file. |
chmod g-w filename | Remove write permission for the group of the file. |
chmod o=r filename | Set read permission for other users of the file. |
chmod a-x filename | Remove execute permission for all users of the file. |
Changing File Ownership
To change the ownership of a file, use the chown command. The chown command takes two arguments: the new owner and the file to change ownership of. The following table lists some examples of how to use the chown command:
| Command | Description |
|---|---|
chown user filename | Change the owner of the file to user. |
chown user:group filename | Change the owner and group of the file to user and group, respectively. |
chown :group filename | Change the group of the file to group. |