As a Windows user transitioning to Linux, I share a critical insight about filesystem permissions that clarified security challenges encountered on my Synology NAS.
The Key Learning
The key learning centers on directory execute permissions. As explained in the Linux Journal:
If a user or group does not have execute permission on a given directory, the user or group is unable to list or read anything in it, regardless of the permissions set on the things inside.
Understanding the Distinction
While having read but not execute permission may sometimes display directory contents through ls, lacking both read and execute permissions prevents access entirely.
This distinction between Windows and Linux permission models is crucial for users migrating between systems.
Execute Permission on Directories
In Linux, execute permission on a directory functions as a "traversal" permission—necessary to access or view anything within that directory, independent of the permissions assigned to individual files inside it.