bash-tutorial/tutorial/changeowner.org

#+options: toc:nil num:nil author:nil

* Changing permissions for files and directories

There are three types of permissions for files and directories in the system:

| Permission    | Files           | Directories       |
|---------------+-----------------+-------------------|
| Read ('r')    | Read the file   | List contents     |
| Write ('w')   | Change the file | Create amd remove |
| Execute ('x') | Execute files   | Access the files  |


Permissions can be differente for different users:

- Owner of the files
- Group: other users in the file's group
- Others

** Creating a file and checking permissions

Here we create a file with the sentence "this is a fancy file". The sentence is
redirected to the name "fancyfile.org" and a new file is created!

#+begin_src bash
  echo "this is a fancy file" > fancyfile.org
#+end_src

#+RESULTS:

In the ouptut of ~ls~ command, there letters showing each permission for each user: owner, group, others, respectively.

#+begin_src bash
  ls -la fancyfile.org
#+end_src

#+RESULTS:
: -rw-r--r-- 1 user user 21 jul 18 06:06 fancyfile.org

** Settings permissions for the file

Setting permissions for the

- User who owns the file = "u"
- Other users in the group = "g"
- Other users = o  

You may change the permissions for each user, using letters (r-w-x):
  
#+begin_src bash
  chmod u=r, g=rw, o=r fancyfile.org
#+end_src

#+RESULTS:

Then it changed!

#+begin_src bash
  ls -la fancyfile.org
#+end_src

#+RESULTS:
: -r--rw-r-- 1 user user 21 jul 18 06:06 fancyfile.org


** Changing permission for directories

Let's say I (unintentionally) changed the permissions for a directory that
contains multiple subdirectories. Let's call that directory "buds"

I can't access the files without being `root`. This is the outuput in the
command line When a list the directory using `ls -la`.

#+begin_example bash
  drw-r--r--  81 user user     4096 dec 26 06:21  buds
#+end_example

When I go to my git repository and check the change I can see this output for
every file within the directory:

#+begin_example bash
  diff --git a/doc/index.rst b/doc/index.rst
  old mode 100644
  new mode 100755
#+end_example

Thus, the directory has the following permissions

- For the owner = read (4) and write (2)
- For the group = read (4)
- For others = read (4)
  
Using ~chmod~ 744 will change the permissions for:

 * The owner (4 = read; 2 = write; 1 = execute)
 * The group (4 = read) and
 * Others (4 = read)

Applying the same logic to a file:

#+begin_src bash
  chmod 744 NameOfFileHere
#+end_src

Use ~-R~ if you want to apply recursive ~chmod~

#+begin_src bash
  chmod -R 755 NameOfFileHere
#+end_src

*** The output now is:

#+begin_example bash
  drwxr-xr-x  81 user user    4096 dec 26 06:21  buds
#+end_example

Remember how it was before

#+begin_example bash
  drw-r--r--  81 user user    4096 dec 26 06:21  buds_before
#+end_example

** Changing owner

But I still can open the files. That is because need to change the owner.

To change the owner of files the command ~chown~ may be used

#+begin_example bash
  chown NameOfownerHere buds # Try this and check the result
#+end_example

Include the owner then ~:~ and then the name of the group to change ownership for each one of those users

#+begin_example bash
    chown user:usergroup buds # Then try this and check the result
#+end_example


ps: should use`sudo` to run this command, so be careful and make a scratch directory
to run tests.

** References

- Check the manual: info -> Coreutils -> File permissions. In bash: ~info coreutils~
  Coreutils are standard programs for text and file manipulation