public/subjects/devops/hard-perm/README.md

hard-perm

Instructions

Create a file hard-perm.sh, which will change the default permissions for the files and folders inside the folder hard-perm, to the ones below:

Right now the folder looks like this:

$ ls -l hard-perm
total 12
drwxrwxr-x 2 user user 4096 dec 13 18:10 0
-rw-rw-r-- 1 user user    0 dec 13 18:11 1
-rw-rw-r-- 1 user user    0 dec 13 18:11 2
drwxrwxr-x 2 user user 4096 dec 13 18:10 3
-rw-rw-r-- 1 user user    0 dec 13 18:11 4
-rw-rw-r-- 1 user user    0 dec 13 18:11 5
-rw-rw-r-- 1 user user    0 dec 13 18:11 6
-rw-rw-r-- 1 user user    0 dec 13 18:11 7
-rw-rw-r-- 1 user user    0 dec 13 18:11 8
-rw-rw-r-- 1 user user    0 dec 13 18:11 9
drwxrwxr-x 2 user user 4096 dec 13 18:10 A

Expected output:

$ ls -l hard-perm
total 12
dr-------x 2 user user 4096 dec 13 17:50 0
-r------w- 1 user user    0 dec 13 17:51 1
-rw----r-- 1 user user    0 dec 13 17:51 2
drwxrwxrwx 2 user user 4096 dec 13 17:51 3
-r-x--x--- 1 user user    0 dec 13 17:51 4
-r--rw---- 1 user user    0 dec 13 17:51 5
-r--rw---- 1 user user    0 dec 13 17:51 6
-r-x--x--- 1 user user    0 dec 13 17:51 7
-rw----r-- 1 user user    0 dec 13 17:51 8
-r------w- 1 user user    0 dec 13 17:51 9
dr-------x 2 user user 4096 dec 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.

$ touch example.txt
$ ls -l example.txt
-rw-rw-r-- 1 user user 348 dec 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.

$ chmod 777 example.txt
$ ls -l example.txt
-rwxrwxrwx 1 user user 348 dec 13 15:31 example.txt
$

You can also achieve the same result using symbolic notation.

$ chmod a+rwx example.txt
$ ls -l example.txt
-rwxrwxrwx 1 user user 348 dec 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.

$ 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:

$ 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
• Symbolic notation