diff --git a/Create-DevTerm-R01-OS-image-from-scratch.md b/Create-DevTerm-R01-OS-image-from-scratch.md
index 7bd72af..619c393 100644
--- a/Create-DevTerm-R01-OS-image-from-scratch.md
+++ b/Create-DevTerm-R01-OS-image-from-scratch.md
@@ -417,4 +417,22 @@ git apply wiringCP0329.patch
 sudo ./build
 #Choice: 2
 
-```
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+```
+
+# For apt upgrade
+
+apt upgrade on R01 os will mess up the content of extlinux.conf  
+lead the boot failed  
+
+so mount the sd card(with R01 os)  on a PC (like Linux )
+
+then go into the **boot partition** of the sd card
+
+you will see 
+```
+extlinux.conf  
+extlinux.conf.cpi.bak  
+```
+replace extlinux.conf  with extlinux.conf.cpi.bak
+
+the **extlinux.conf.cpi.bak** is for this kind of situation
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