How does chown affect permissions?

The chown command itself does not directly change the permissions of a file or directory; rather, it changes the ownership. However, ownership is closely tied to permissions in Linux, and understanding this relationship is crucial.

How Ownership Affects Permissions

User Ownership: The owner of a file or directory has specific permissions defined by the permission settings. For example, if a file is owned by user A, that user may have read, write, or execute permissions based on the permission settings.
Group Ownership: Files also have a group associated with them. Users who are part of that group may have different permissions than the owner. For instance, if a file is owned by group B, members of group B may have access rights that differ from those of the file's owner.
Other Users: Permissions for users who are neither the owner nor part of the group are defined under "others." These permissions can be more restrictive.

Example Scenario

Consider a file with the following permissions:

-rw-r----- 1 alice dev  100 Oct 1 12:00 example.txt

Owner: alice (read and write permissions)
Group: dev (read permissions)
Others: No permissions

If you change the ownership of this file to bob using:

sudo chown bob example.txt

Now, bob becomes the owner of the file. If bob does not belong to the dev group, he will only have the permissions defined for "others," which in this case means he has no access to the file.

Summary

While chown changes who owns a file or directory, the actual permissions that apply depend on the permission settings for the new owner and their group. Therefore, changing ownership can effectively alter who can access or modify a file, depending on the existing permission settings.

If you have further questions or need more examples, feel free to ask!