Adds linux basic command notes on permissions

Linux/basic_cmd.md

@@ -1,4 +1,4 @@
-# Theory
+# Linux 
 
 ## Absolute Path vs Relative Path in Linux/Unix
 One of this blog follower asked us that whatâs the difference between absolute and relative path?
@@ -41,15 +41,19 @@ Examples of relative path and absolute path for the same operation.
 - Man: an interface to the on-line reference manuals 
 > $ man ls
 
-# Wildcard
+## Wildcard
 * Show all picture (multiple char)
 > $ ls pic*  
+
 ? show only picture between 50 and 59 (only one char)
+
 > $ ls pic5?.jpg  
+
 [] show only if char in [p-P]
+
 > $ ls [pP]ic*
 
-# Files and directory
+## Files and directory
 
 - ls: list directory contents
 > $ ls
@@ -60,31 +64,35 @@ Examples of relative path and absolute path for the same operation.
 - Pwd: output the current working directory
 > $ pwd
 
-- Change directory
+- Cd: Change directory
 > $ cd    
+
 back to previous folder
 > $ cd -   
 
-- Make directory
+
+- Mkdir: Make directory
 > $ mkdir test1 test2 test3
 
 > $ mkdir -p lol/lol/lol     
+
 -p to create parent directory if needed
 
-- Remove directory
+- Rmdir: Remove directory
 
 > rmdir filename
 
 > rm -rf filename
 
-- Move directory (can be used to rename a file)
+- Mv: Move directory (can be used to rename a file)
 > mv file /opt/movedfile
 
-- Copy file or directory
+- Cp: Copy file or directory
 > $ cp file /opt/newcopiedfile 
 
-- Touch - change file timestamps but it can also create files 
+- Touch: change file timestamps but it can also create files   
 > $ touch nomdefichier.md  
+
 > $ touch pic{00..99}.jpeg # does not work
   
 - Which: Searching the PATH for executable files matching the names of the arguments
@@ -105,7 +113,8 @@ back to previous folder
 - Cat: concatenate files and print on the standard output
 
 > $ cat filename
-## Users and privileges
+
+## Users
 
 adduser, addgroup - add a user or group to the system
 > sudo adduser steve
@@ -132,7 +141,7 @@ Enter the new value, or press ENTER for the default
 	Other []: 
 Is the information correct? [Y/n] y
 
-````
+```
 
 user skeleton: skeleton files used for new user configuration 
 > $ ls /etc/skel/
@@ -147,7 +156,7 @@ user skeleton: skeleton files used for new user configuration
 - Change user
 > $ su - marie
 
-### Permissions
+## Permissions
 
 - Chmod: change file mode bits
 
@@ -159,6 +168,8 @@ A  combination of the letters **ugoa** controls which users' access to the file
 
 If none of these are given, the effect is as if (a) were given, but bits that are set in the umask are not affected.
 
+![file permissions](./img/file_permission.png)
+
 ```bash
 marie@d3bi4n:~$ ls -l
 total 4
@@ -173,7 +184,9 @@ total 4
 
 > -rw-r--**rw**- 1 marie marie 12 Apr  7 05:44 test
 
-###groups
+
+Number alternatives: 
+### Groups
 
 Groups: print the groups a user is in
 > $ groups