docs(hard-perm): improve the readme

subjects/devops/hard-perm/README.md

@@ -43,9 +43,70 @@ dr-------x 2 user user 4096 dez 13 17:50 A
 
 ### Hints
 
+- The `chmod`, or change mode, command allows an administrator to set or modify a file’s permissions. Every UNIX/Linux file has an owner user and an owner group attached to it, and every file has permissions associated with it. The permissions are as follows: read, write, or execute.
+
+This is what the default permissions looks like when you create a file.
+
+```console
+$ touch example.txt
+$ ls -l example.txt
+-rw-rw-r-- 1 user user 348 dez 13 15:31 example.txt
+$
+```
+
+This is what it looks like if you want to give permissions to read, write and execute to every group.
+
+```console
+$ chmod 777 example.txt
+$ ls -l example.txt
+-rwxrwxrwx 1 user user 348 dez 13 15:31 example.txt
+$
+```
+
+You can also achieve the same result using symbolic notation.
+
+```console
+$ chmod a+rwx example.txt
+$ ls -l example.txt
+-rwxrwxrwx 1 user user 348 dez 13 15:31 example.txt
+$
+```
+
+In this example we use:
+
+- `"a"` which is a shorthand for user `"u"`, group `"g"`, and others `"o"`.
+
+- The `"+"` sign which specifies that permissions will be added.
+
+- `"rwx"` which is a shorthand for read `"r"`, write `"w"`, and execute `"x"`.
+
+**Symbolic links**, also known as symlinks, are files that act as pointers or aliases to other files or directories on a file system.
+
+To modify the permissions of a `symbolic link`, you would use the same `chmod` command as you would for a regular file or directory. However, the permissions that you set will apply to the `link` itself, not the file or directory that it points to.
+
+```console
+$ ls -l my_link
+lrwxrwxrwx 1 user user  11 Apr  3 17:35 my_link -> target_file
+$
+```
+
+The `l` at the beginning of the string indicates that this is a symbolic link, and the next nine characters `rwxrwxrwx` indicate the permissions of the link. The last column `my_link -> target_file` indicates the name of the link followed by an arrow `->` and the name of the target file.
+
+Here are some examples of using chmod with `symbolic links`:
+
+```console
+$ ls -l my_link
+lrwxrwxrwx 1 user user  11 Apr  3 17:35 my_link -> target_file
+$ chmod 600 my_link
+$ ls -l my_link
+lrw------- 1 user user  11 Apr  3 17:35 my_link -> target_file
+$
+```
+
 > You have to use Man or Google to know more about commands flags, in order to solve this exercise!
 > Google and Man will be your friends!
 
 ### References
 
 - [Chmod](https://www.linode.com/docs/guides/modify-file-permissions-with-chmod/#modify-file-permissions-with-chmod)
+- [Symbolic notation](https://www.linode.com/docs/guides/modify-file-permissions-with-chmod/#using-symbolic-notation-syntax-with-chmod)