rwxrwxrwt 1 nobody wheel 0 Feb 23 17:07 testĬhanges the ownership of the file to nobody and the group to wheel. It is revealed now that the file is owned by the userid ‘nobody’ and not by ‘yorgos’ anymore. rwxrwxrwt 1 nobody staff 0 Feb 23 17:07 test Have in mind, though, that you must have root access in order to change the ownership of a file. The first example is used to change the owner of a file to another one. The chown command accepts various parameters that alter its behaviour in some way, but the most commonplace usage is the following: You can also change file and group ownership of a file by using the chown command. If you want to see more examples, do consult the manual page for chmod by issuing the following command: Here we see the last flags all unset to “-”. rwxrwx- 1 yorgos staff 0 Feb 23 17:07 test They would not be able to either read, write or execute the file: Or maybe you need to lock out everyone else completely. rwxrwxrwx 1 yorgos staff 0 Feb 23 17:07 test So, let’s say that you want to give execute permissions to the users belonging to the group (but make sure you are the owner of the file first!): There are a couple of others, but we will discuss those in the final section of our article. The is specified by the following symbols: The chmod command accepts a variety of parameters that change its behaviour in many different ways, but its general use is the following: The command we are going to use is called chmod (change file mode). In order to modify the permissions of a file or folder, again, you either use a GUI command (this is outside the scope of this article, so we won’t go there) or use certain linux commands in your terminal. So in effect, this just means “this file can be read and written by the owner, and it is read-only by everyone else”. Lastly, these permissions concern everyone else. R– : read permission, no write and execute. These permissions regard users belonging to a group.

R– : read permission, no write and execute permission. Rw- : read and write permissions (no execute). – : Filetype (this can contain l, -, or d)

Continuing, let’s break down the permissions field: Since the first character/flag in our example is “-”, we are talking about a simple file. The file types can be: “-” for files, “l” for symbolic links (these are file system links that just point to another file) and “d” for directories. The first one shows the file type flag while the latter indicate the permissions themselves. You will notice that there are 9 different combinations of permission groups and types, but 10 flag positions. how many links there are to this file (1).The rest of the fields from left to right display the following information: The string “-rw-r–r–” contains the file system permission information that we are interested in. rw-r–r– 1 yorgos staff 0 Feb 23 17:07 test Open your terminal and type the following command: You can view a file or folder’s permissions by either using a GUI file manager or by inspecting the output of the ls command in the console terminal. The permission group ones are used in commands that change the ownership and group of a file, which we will delve into shortly. Unset flags are depicted with a “-” character. The permission types are the characters “r”, ”x” and “w”, called flags, and are displayed as such if you list the file’s or folder’s permissions in some way.

Three permission types: r, read, x, execute, w, write.Three permission groups: u for owner, g, group, o or a, all users.Permission groups and typesĪll file and folder access control is defined in the filesystem using the following information: However, they are quite easy to grasp, once you understand the logic behind them. Linux’s filesystem permission model stems from the legacy of UNIX. Linux file permissions may seem like arcane number theory hieroglyphics to some and it’s understandable.

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