Add variable/option to control if zeros are written to the disk

It takes some time to write zeros to the disk and it aborts later if
less than 20GB are available.

Add variable to the template, cleanup script and add a new option to
wrapacker.

arch-template.json

@@ -4,6 +4,7 @@
         "iso_checksum_url": "https://mirrors.kernel.org/archlinux/iso/{{isotime \"2006.01\"}}.01/sha1sums.txt",
         "ssh_timeout": "20m",
         "country": "US",
+        "write_zeros": "true",
         "headless": "false"
     },
     "builders": [
@@ -124,7 +125,7 @@
         },
         {
             "type": "shell",
-            "execute_command": "{{ .Vars }} sudo -E -S bash '{{ .Path }}'",
+            "execute_command": "{{ .Vars }} WRITE_ZEROS={{ user `write_zeros` }} sudo -E -S bash '{{ .Path }}'",
             "script": "scripts/cleanup.sh"
         }
     ],

scripts/cleanup.sh

@@ -5,8 +5,10 @@ echo ">>>> cleanup.sh: Cleaning pacman cache.."
 /usr/bin/pacman -Scc --noconfirm
 
 # Write zeros to improve virtual disk compaction.
-echo ">>>> cleanup.sh: Writing zeros to improve virtual disk compaction.."
-zerofile=$(/usr/bin/mktemp /zerofile.XXXXX)
-/usr/bin/dd if=/dev/zero of="$zerofile" bs=1M
-/usr/bin/rm -f "$zerofile"
-/usr/bin/sync
+if [[ $WRITE_ZEROS == "true" ]]; then
+  echo ">>>> cleanup.sh: Writing zeros to improve virtual disk compaction.."
+  zerofile=$(/usr/bin/mktemp /zerofile.XXXXX)
+  /usr/bin/dd if=/dev/zero of="$zerofile" bs=1M
+  /usr/bin/rm -f "$zerofile"
+  /usr/bin/sync
+fi

wrapacker

@@ -64,7 +64,7 @@ validate_country() {
 # print this script's usage message to stderr
 usage() {
   cat <<-EOF >&2
-  usage: wrapacker [-c COUNTRY] [-p PROVIDER] [-t TIMEOUT] [-o ON-ERROR ACTION] [-f] [-d] [-h]
+  usage: wrapacker [-c COUNTRY] [-p PROVIDER] [-t TIMEOUT] [-w] [-o ON-ERROR ACTION] [-f] [-d] [-h]
 EOF
 }
 
@@ -129,6 +129,9 @@ help() {
               sets the amount of time packer will wait for trying ssh login;
               defaults to 20m
 
+       -w, --skip-write-zeros
+              don't inflate the disk to improve virtual disk compaction
+
        -o, --on-error=ACTION
               error handling if the build fails;
               defaults to cleanup
@@ -165,6 +168,7 @@ country=''
 provider=''
 dry_run=false
 timeout=''
+skip_write_zeros=false
 on_error=''
 force=false
 headless=false
@@ -193,6 +197,9 @@ while [[ $1 != '' ]]; do
     --timeout=*)
       timeout=${1#*=}
       ;;
+    -w | --skip-write-zeros)
+      skip_write_zeros=true
+      ;;
     -o | --on-error)
       on_error=$2
       shift
@@ -288,6 +295,12 @@ else
   SSH_TIMEOUT='20m'
 fi
 
+if [[ $skip_write_zeros = true ]]; then
+  WRITE_ZEROS="false"
+else
+  WRITE_ZEROS="true"
+fi
+
 if [[ $on_error ]]; then
   case $(echo "$on_error" | tr '[:upper:]' '[:lower:]') in
     cleanup)
@@ -320,6 +333,7 @@ cat <<-EOF
     -var "ssh_timeout=$SSH_TIMEOUT" \\
     -var "country=$country" \\
     -var "headless=$headless" \\
+    -var "write_zeros=$WRITE_ZEROS" \\
     -on-error=$ON_ERROR \\
     -force \\
     arch-template.json
@@ -333,6 +347,7 @@ cat <<-EOF
     -var "ssh_timeout=$SSH_TIMEOUT" \\
     -var "country=$country" \\
     -var "headless=$headless" \\
+    -var "write_zeros=$WRITE_ZEROS" \\
     -on-error=$ON_ERROR \\
     arch-template.json
 EOF
@@ -346,6 +361,7 @@ else
       -var "ssh_timeout=$SSH_TIMEOUT" \
       -var "country=$country" \
       -var "headless=$headless" \
+      -var "write_zeros=$WRITE_ZEROS" \
       -on-error=$ON_ERROR \
       -force \
       arch-template.json
@@ -357,6 +373,7 @@ else
       -var "ssh_timeout=$SSH_TIMEOUT" \
       -var "country=$country" \
       -var "headless=$headless" \
+      -var "write_zeros=$WRITE_ZEROS" \
       -on-error=$ON_ERROR \
       arch-template.json
   fi