What is File Permission in Linux and what's necessary to know as a programmer or developer

What is File Permissions in Linux and why I need to know about it as a programmer or Develope

Permission is a very important function to keep things organized and secure. Even as the owner you do not want to have full permissions over certain files. Imagine you're working on a project and somehow accidentally deleted the file before you'd the change to upload it to git or to some secure place. Same with other users, you do not want them to be able to accidentally or deliberately delete, write or execute particular files.

Permission modes

There exist 3 permissions or modes, and 3 type of people whom you may grant them.

Three permissions are: Read, Write and Execute and they're represented by r, w, x. They're always in the same order(you'll see when we use terminal). Read is where system will allow them to read/open the file. Write is permission to write/edit the file, and last buy not least Execute is permission to execute or run a file.

The 3 type of people I mentioned above are: Owner/User, Group and Other. Represented by u, g, o. Also there's All, means everyone indicated by letter a. Owner is the person/user who created the file, Group is collection of users, others is everyone else.

ls -l to see permissions

To check permission details just navigate to directory and type ls -l. The -l argument shows detailed information about the file including it's permissions. I typed the command and here's the permission it returned. drwxr-xr-x

Starting to read from very left to right, the d even dumbest person can can represents directory. Now lets go 3 letters at a time, keep the order in mind(u, g, o) first 3 letters rwx are for Owner, that's the permissions the owner has, he can read, write and execute. Next 3 letters are r-x, and they're for group, users in group can read, - means the permission is not set, ad execute. Lastly we've permissions for Others r-x, they can read, - permission is not set, and execute.

Along with permissions you'll also have other rows,  next to permission will be number of files or links in that directory, then then of the owner or user who owns the file, then the group the file belongs to.

nautilus

Permissions on ubuntu can also be set or changed using the Gui program nautilus, but only if you execute it as administrator. If you type sudo nautilus in terminal a new window file manager/exporer window will pop up where you can navigate to desired directory, right click on file or folder and set the permissions or each individual person.

chmod

chmod means change mode, it allow you to change permissions/modes on files and directories. The format for this command is "chmod options permissions filename". Options are arguments it can take, permissions are as usual r, w, x and filename you should already know. Note that options aren't always necessary.

Options for chmod

-f, --silent, --quiet suppress most error messages
-v, --verbose output a diagnostic for every file processed
-c, --changes like verbose but report only when a change is made --reference=RFile use RFile's mode instead of MODE values
-R, --recursive change files and directories recursively
--help display help and exit --version output version information and exit

Permission setting Example

Lets say I want to grant whichever group Documents directory belong to permissions to read, write and execute. Note that all the users will then be able to read, write and execute.

Here's what we do:
1. Enter chmod command first of all.
2. For permissions we tell who we want to grant permissions to , u, g, or o.
3. We use + or - symbol letting the command know whether we're setting or removing permissions. For example, if you want to give user permission to only read and execute, but not edit. We do +r-w+x.
4. We type the permissions.
5. Write file name at the end.

1. chmod | 2. g | 3. + | 4. rwx | 5. Documents
Here's my permissions for Documents folder "dr-xr-xr-x". Lets say I want to give:
- User permission to read, write and execute.
- Group permission to only read.
- Other permissive to only read aswell.

chmod u+rwx,g+r-w-x,o+r-w-x Documents

This will change the permissions as we needed. If you go ahead and do ls -l you should see these permissions for Document directory "drwxr--r--"

If you'd like to know more about chmod I suggest learning about using shorthand numeric values as permissions instead of messy -rwx+rx letters.

I hope this guide's been information. See you guys next time.