diff --git a/Linux/basic_cmd.md b/Linux/basic_cmd.md
index 5d34f85..93d6ec6 100644
--- a/Linux/basic_cmd.md
+++ b/Linux/basic_cmd.md
@@ -1,5 +1,33 @@
+# Theory
+
+## Absolute path
+cd /etc
+## relative path
+../../../etc
 # Basic Linux Command
 
+list current directory
+> $ ls -l -a -r -t -h --help
+ls = program
+-l -a = parameters
+
+Man for manual
+> $ man ls
+
+print working directory
+> $ pwd
+
+change directory
+> $ cd 
+back to precedent forlder
+> $ cd -
+
+Make directory
+> $ mkdir test1 test2 test3
+
+> $ mkdir -p lol/lol/lol   
+-p to create parent directory if needed
+
 Searching the PATH for executable files matching the names of the arguments
 > $ which ls