Contents.Understanding and Using File PermissionsIn Linux and Unix, everything is a file. Directories are files, files are files and devices are files. Devices are usually referred to as a node; however, they are still files. All of the files on a system have permissions that allow or prevent others from viewing, modifying or executing.
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The only permission on folder A that matters is the search (execute) permission: if you don't have it you can't descend to folder B. Other than that there is no relation between permissions of A and B, for example if A is read-only and B is not, or even if you don't even have read permission to A, you still can create and delete files in B. Aug 08, 2015 Linux Command Line Tutorial For Beginners 17 - file permissions, symbolic permissions and chmod - Duration: 12:28. ProgrammingKnowledge 30,449 views.
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If the file is of type Directory then it restricts different actions than files and device nodes. The super user 'root' has the ability to access any file on the system. Each file has access restrictions with permissions, user restrictions with owner/group association. Permissions are referred to as bits.To change or edit files that are owned by root, sudo must be used - please see for details.If the owner read & execute bit are on, then the permissions are: -r-x-There are three types of access restrictions.
Can someone explain to me how directory permissions are inherited in Linux (Ubuntu, specifically)?For example, what if I have the following directory structure: folderAfolderBDo folderA's permissions always override folderB's? Is there any difference if folderA's permissions are more restrictive than folderB's, or vice-versa?My guess would be that if folderB had more restrictive permissions, it would override folderA's, but if folderA had more restrictive permissions, then it would override its children. I like to think of folders as Gatekeepers. Each folder's permissions allow to you view that folder and any below it. Once you are past one Gatekeeper, you are past it, and the permissions involved in that folder no longer matter.More specifically, the execute permission on folders is actually the ability to enter(list the files within) it. Each file has the permission on whether it is write/read/executable.So, as long as you have the permissions to view/read the files inside one folder, you can move into a child folder and do whatever that folder gives you permission to do.