Merge lp:~smoser/maas-images/trunk.better-check-overlay into lp:maas-images

[Scott Moser]

bin/kpack-from-image: better determine if overlay support is available.

Instead of assuming that mount-image-callback having a flag '--overlay'
indicates that overlay support is usable, further check.

This makes the --copy=auto (the default) work in scenarios where
there are no modules available for loading or kernel module loading
is not allowed.

[lp:~smoser/maas-images/trunk.better-check-overlay]

335. By Scott Moser on 2016-10-03

load the module by fs-<filesystem>

this is a better path to loading a kernel module since
we're askign for a specific filesystem support, this will load
that filesystem rather than assuming that 'overlay' module
provides the 'overlay' filesystem.

[Scott Moser (smoser)]

This isn't needed now as the fix went into cloud-itils for mic.

Unmerged revisions

335. By Scott Moser on 2016-10-03

load the module by fs-<filesystem>

this is a better path to loading a kernel module since
we're askign for a specific filesystem support, this will load
that filesystem rather than assuming that 'overlay' module
provides the 'overlay' filesystem.

334. By Scott Moser on 2016-10-03

bin/kpack-from-image: better determine if overlay support is available.

Instead of assuming that mount-image-callback having a flag '--overlay'
indicates that overlay support is usable, further check.

This makes the --copy=auto (the default) work in scenarios where
there are no modules available for loading or kernel module loading
is not allowed.

=== modified file 'bin/kpack-from-image'
--- bin/kpack-from-image	2016-03-03 17:11:42 +0000
+++ bin/kpack-from-image	2016-10-03 16:07:24 +0000
@@ -241,6 +241,26 @@
     "$@"
 }
 
+can_use_overlay() {
+    mount-image-callback --help | grep -q -- --overlay || {
+        debug 1 "Cannot use overlay due to no mount-image-callback support"
+        return 1
+    }
+    local mod="" mods="overlay overlayfs"
+    for mod in $mods; do
+        awk '-F\t' '$2 == mod { e=0; } END {exit(e);}' \
+            e=1 "mod=$mod" /proc/filesystems && {
+                debug 1 "Support overlay through '$mod' in /proc/filesystems"
+                return 0
+            }
+    done
+    for mod in $mods; do
+        modprobe --quite --use-blacklist "fs-$mod" && return 0
+    done
+    debug 1 "No support in /proc/filesystems for overlay."
+    return 1
+}
+
 chrooted() {
     # this is expected to run chrooted inside the root
     # installs all packages (arguments), writes kernel
@@ -431,7 +451,7 @@
     trap cleanup EXIT
 
     if [ "$copy" = "auto" ]; then
-        if mount-image-callback --help | grep -q -- --overlay; then
+        if can_use_overlay; then
             copy="overlay"
         elif command -v qemu-img >/dev/null 2>&1; then
             copy="qcow"