[Ovirt-devel] [RFC][PATCH] ovirt-node-image : edit-livecd : fail on error in arbitrary code

[abhishek misra]

Purpose : fail iso build on encountering error in arbitrary code '$CODE'

1.    export 'WDIR' , for 'CODE' to pick-up location to create 'fail'  
file to indicate failure, note that it may not always be possible to 
return some error code on failure in 'CODE'
2.    'set' commands enclosing 'CODE' will not be required
3.    'CODE' is expected to use 'set -e and trap signals like EXIT 
(which are generated when some command fails ) and write a 'fail' file
4.    look for 'fail' file once 'CODE'  has completed
       if positive then unmount proc ( note that if 'CODE', proc still 
remains mounted; this is not unmounted by existing trap in edit-livecd 
script  )
       rest of the cleanup is taken care off by existing trap statement

Signed-off-by: Abhishek Misra <fishy at linux.vnet.ibm.com>

---

--- a/edit-livecd    2009-11-10 17:23:21.000000000 +0530
+++ b/edit-livecd    2009-11-10 18:39:11.000000000 +0530
@@ -159,13 +159,14 @@ cp -pr $WDIR/sq $WDIR/sq-w
 # mount root filesystem
 mnt "-t ext2 $WDIR/sq-w/LiveOS/ext3fs.img -o rw,loop" ex
 
+# exporting for tarp in 'CODE'
+# $CODE can 'trap' EXIT signal and touch '$WDIR/fail' to notify this 
script of its failure
+
 echo ">>> Updating CD content"
 if [ -n "$CODE" ]; then
     (
       cd $WDIR/ex
-      set +e
       eval "$CODE"
-      set -e
     )
 else
     echo "***"
@@ -174,6 +175,14 @@ else
     read
 fi
 
+# exit if $CODE failed. Look if '$WDIR/fail' exists
+if [ -a $WDIR/fail ] ; then
+    rm $WDIR/fail
+    # need to explictly look for proc as failure in $CODE leaves it 
mounted causing 'umount $WDIR/ex-rw' to fail
+    mount | grep livecd | grep proc && addExit "umount -v $WDIR/ex-rw/proc"
+    exit
+fi
+
 # Try to unmount.  But this is likely to fail, so let the user retry,
 # e.g., if he forgot to "cd" out of $WDIR/ex.
 while :; do