On s390x, zipl bootloader cannot handle /boot on btrfs. LP: #1609140

check.d/no_btrfs_boot

@@ -1,9 +1,19 @@
 #!/bin/sh
-# grub and other bootloaders that read the filesystem do not support /boot
-# on btrfs. (lilo should work). Detect and warn.
+# most bootloaders that read the filesysm do support /boot on
+# btrfs. Some are known not to work, e.g. zipl on s390x. Detect and
+# warn.
 
 . /lib/partman/lib/base.sh
 
+ARCH="$(archdetect)"
+case $ARCH in
+    s390x/*)
+        ;;
+    *)
+        exit 0
+        ;;
+esac
+
 get_btrfs_root_boot () {
 	(for i in /lib/partman/fstab.d/*; do
 		[ -x "$i" ] || continue

debian/changelog

@@ -1,3 +1,9 @@
+partman-btrfs (22) UNRELEASED; urgency=medium
+
+  * On s390x, zipl bootloader cannot handle /boot on btrfs. LP: #1609140
+
+ -- Dimitri John Ledkov <xnox@ubuntu.com>  Tue, 04 Oct 2016 13:15:35 +0100
+
 partman-btrfs (21) unstable; urgency=medium
 
   [ Nicholas D Steeves ]

debian/partman-btrfs.templates

@@ -23,7 +23,7 @@ _Description: btrfs root file system not supported without separate /boot
  Your root file system is a btrfs file system. This is not supported
  by the boot loader used by default by this installer.
  .
- You should use a small /boot partition with another file system, such as ext3.
+ You should use a small /boot partition with another file system, such as ext4.
 
 Template: partman-btrfs/btrfs_boot
 Type: error
@@ -32,4 +32,4 @@ _Description: btrfs file system not supported for /boot
  You have mounted a btrfs file system as /boot. This is not supported
  by the boot loader used by default by this installer.
  .
- You should use another file system, such as ext3, for the /boot partition.
+ You should use another file system, such as ext4, for the /boot partition.