update

linux.ipynb

@@ -1530,7 +1530,48 @@
   {
    "cell_type": "markdown",
    "metadata": {},
-   "source": []
+   "source": [
+    "**Managing permissions using `chmod`**  \n",
+    "`$ chmod u=<rwx>,g=<rwx>,o=<rwx> <filename>`"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "`$ chmod u=rw,g=rw,o=r somefile`"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "```\n",
+    "$ touch file2\n",
+    "$ ls -l file2\n",
+    "$ sudo chmod u=r,g=rwx,o=r file2\n",
+    "$ ls -l file2\n",
+    "```"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "Use + and - to toggle on or off specific permissions  \n",
+    "`$ sudo chmod g-w file2`  -- removes the write permission from the group on the file  \n",
+    "`$ ls -l file2`"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "**Change Permissions Numerically**  \n",
+    "`$ touch file3`  \n",
+    "`$ ls -l file3`  \n",
+    "`$ chmod 660 file3`"
+   ]
   },
   {
    "cell_type": "markdown",