From 2cad265bad5309aac14a80505ebd5d4c3865e95c Mon Sep 17 00:00:00 2001
From: Michael Meffie <mmeffie@sinenomine.net>
Date: Sun, 18 Aug 2019 10:56:11 -0400
Subject: [PATCH] Resume interrupted downloads (#39)

Currently, if an image download is interrupted or fails, a partial file
is left in the image directory and a subsequent kvm-install-vm create
command will blissfully use the partial image, which then silently fails
to create the guest.

Instead, name the files with the '.part' file extension while the file
download is in progress, then pivot to the real image name after the
download is complete.  Use the wget '--continue' option to resume
partial downloads so we don't have to restart the download from the
beginning.
---
 kvm-install-vm | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/kvm-install-vm b/kvm-install-vm
index 11f5fc2..2c7a2e5 100755
--- a/kvm-install-vm
+++ b/kvm-install-vm
@@ -307,10 +307,23 @@ function fetch_images ()
 
     if [ ! -f ${IMAGEDIR}/${QCOW} ]
     then
-        output "Cloud image not found.  Downloading"
         set_wget
-        ${WGET} --directory-prefix ${IMAGEDIR} ${IMAGE_URL}/${QCOW} || \
+        if [ -f ${IMAGEDIR}/${QCOW}.part ]
+        then
+            CONTINUE="--continue"
+            output "Partial cloud image found.  Resuming download"
+        else
+            CONTINUE=""
+            output "Cloud image not found.  Downloading"
+        fi
+        ${WGET} \
+            ${CONTINUE} \
+            --directory-prefix ${IMAGEDIR} \
+            --output-document=${IMAGEDIR}/${QCOW}.part \
+            ${IMAGE_URL}/${QCOW} || \
             die "Could not download image."
+
+        mv ${IMAGEDIR}/${QCOW}.part ${IMAGEDIR}/${QCOW}
     fi
 
 }