fix: correct some errors

The file "auth.log" is located in /var/log and not at the root of /var.
The file "autofs.fifo-var-autofs-ifb" doesn't exist anymore, the corresponding question has been removed.
The file ".bash_history" might be missing, we create it first just in case.

4_unix_file_system.Rmd

@@ -116,7 +116,7 @@ What is the content of `/dev/null`?
 
 Storage space for variables and temporary files, like system logs, locks, or file waiting to be printed...
 
-In the file `auth.log` you can see the creation of the `ubuntu` and `etudiant `account. To visualize a file you can use the command
+In the file `/var/log/auth.log` you can see the creation of the `ubuntu` and `etudiant `account. To visualize a file you can use the command
 
 ```sh
 less [file_path]
@@ -126,9 +126,7 @@ You can navigate the file with the navigation arrows. Which group the user `ubun
 
 To close the `less` you can press `Q`. Try the opposite of `less`, what are the differences ?
 
-What is the type of the file `autofs.fifo-var-autofs-ifb` in the `run` folder ? From **fifo** in the name, can you guess the function of the `p` file ?
-
-There are few examples of the last type of file in the `run` folder, in which color the command `ls -l` color them ?
+There are few examples of type `p` files in the `run` folder, in which color the command `ls -l` color them ?
 
 ### `/tmp`
 
@@ -162,6 +160,7 @@ The first argument after the option of the `ln` command is the target of the lin
 
 ```sh
 cd
+touch .bash_history
 ln -s .bash_history bash_history_slink
 ls -la
 ```