Update i_u_m_update.md

docs/i_u_m_update.md

@@ -13,17 +13,6 @@ If it needs to, it will ask you how you wish to proceed.
 Merge errors will be reported.
 Some minor conflicts will be auto-corrected (in favour for the mailcow: dockerized repository code).
 
-### I forgot what I changed before running update.sh
-
-See `git log --pretty=oneline | grep -i "before update"`, you will have an output similar to this:
-
-```
-22cd00b5e28893ef9ddef3c2b5436453cc5223ab Before update on 2020-09-28_19_25_45
-dacd4fb9b51e9e1c8a37d84485b92ffaf6c59353 Before update on 2020-08-07_13_31_31
-```
-
-Run `git diff 22cd00b5e28893ef9ddef3c2b5436453cc5223ab` to see what changed.
-
 ### Options
 
 ```
@@ -52,6 +41,30 @@ Run `git diff 22cd00b5e28893ef9ddef3c2b5436453cc5223ab` to see what changed.
 ./update.sh --prefetch
 ```
 
+### I forgot what I changed before running update.sh
+
+See `git log --pretty=oneline | grep -i "before update"`, you will have an output similar to this:
+
+```
+22cd00b5e28893ef9ddef3c2b5436453cc5223ab Before update on 2020-09-28_19_25_45
+dacd4fb9b51e9e1c8a37d84485b92ffaf6c59353 Before update on 2020-08-07_13_31_31
+```
+
+Run `git diff 22cd00b5e28893ef9ddef3c2b5436453cc5223ab` to see what changed.
+
+### Can I role back?
+
+Yes.
+
+See the topic above, instead of diff, run...
+
+```
+docker-compose down
+# Replace commit ID 22cd00b5e28893ef9ddef3c2b5436453cc5223ab by your ID
+git checkout 22cd00b5e28893ef9ddef3c2b5436453cc5223ab
+docker-compose up -d
+```
+
 ## Manual update (not maintained anymore, please use update.sh)
 
 ### Step 1