Merge lp:~mvo/ubuntu/wily/initramfs-tools-ubuntu-core/new into lp:ubuntu/wily/initramfs-tools-ubuntu-core

[Michael Vogt]

[Stéphane Graber (stgraber)]

One concern here is that your / is now effectively backed by a read-write filesystem which you can't unmount, so that may well lead to dataloss unless your shutdown sequence has extra logic to remount every layer read-only properly, killing any task with r/w fds open and only then shutdown.

If you can confirm that your shutdown sequence succeeds at remounting everything read-only prior to system shutdown, then except for the few things I listed in-line, this should be fine.

[Oliver Grawert (ogra)]

my main problem with this approach is that i can edit files under /writable/system-data/os/ubuntu-core.sideload/${snappy_os}/* at any time so there isn't actually a readonly / after all (and i think the bind mount would even immediately reflect the changes i made in the writable source dir)

either use an img file that we ship and loop mount from /writable/system-data/os/ubuntu-core.sideload/${snappy_os}/a-rootfs.img|b-rootfs.img or move it to /system-boot/a/rootfs.img and /system-boot/b/rootfs.img (the latter would really be my preferred approach so that you can just re-format /writable to go back to a factory state and/or even make the u-d-f image smaller by simply having a 1byte writable partition created from u-d-f that we grow on first boot. this would also make any kind of installer setup easier)

[Stéphane Graber (stgraber)]

That's indeed true. That problem could be partly worked around by having a default apparmor policy block such access, but still, ultimately your system is running from writable storage, which makes it prone to corruption and so not very reliable for partial updates or even integrity checks.

[lp:~mvo/ubuntu/wily/initramfs-tools-ubuntu-core/new]

23. By Michael Vogt on 2015-09-11

mount squashfs from writable

24. By Michael Vogt on 2015-09-11

add writable to generated fstab

25. By Michael Vogt on 2015-09-11

scripts/ubuntu-core-rootfs: do not hardcode ext4

26. By Michael Vogt on 2015-09-11

add comment why we can't mount writable RO in the intird and do the writable transition later

27. By Michael Vogt on 2015-09-11

fix silly typo

28. By Michael Vogt on 2015-10-06

merged trunk

29. By Michael Vogt on 2015-10-19

update for new snapfs os/kernel vars

30. By Michael Vogt on 2015-10-19

support both old and new style boots

31. By Michael Vogt on 2015-10-19

re-add "other" mounting

Unmerged revisions

31. By Michael Vogt on 2015-10-19

re-add "other" mounting

30. By Michael Vogt on 2015-10-19

support both old and new style boots

29. By Michael Vogt on 2015-10-19

update for new snapfs os/kernel vars

28. By Michael Vogt on 2015-10-06

merged trunk

27. By Michael Vogt on 2015-09-11

fix silly typo

26. By Michael Vogt on 2015-09-11

add comment why we can't mount writable RO in the intird and do the writable transition later

25. By Michael Vogt on 2015-09-11

scripts/ubuntu-core-rootfs: do not hardcode ext4

24. By Michael Vogt on 2015-09-11

add writable to generated fstab

23. By Michael Vogt on 2015-09-11

mount squashfs from writable

22. By Michael Vogt on 2015-09-02

ensure / is RO and /writable is RW

=== modified file 'scripts/ubuntu-core-rootfs'
--- scripts/ubuntu-core-rootfs	2015-08-24 13:54:01 +0000
+++ scripts/ubuntu-core-rootfs	2015-10-19 10:33:17 +0000
@@ -147,60 +147,10 @@
 	done
 }
 
-#---------------------------------------------------------------------
-# XXX: Entry point - called by the initramfs "/init" script.
-#---------------------------------------------------------------------
-mountroot()
+fsck_writable()
 {
-	local writable_label="writable"
-
-	local writable_mnt="/tmpmnt_${writable_label}"
-
-	pre_mountroot
-
-	[ "$quiet" != "y" ] && log_begin_msg "Running /scripts/local-premount"
-	run_scripts /scripts/local-premount
-	[ "$quiet" != "y" ] && log_end_msg
-
-	# There are 2 root partitions but grub tells us which to boot
-	# with via "root="
-	for x in $(cat /proc/cmdline); do
-		case "${x}" in
-		root=*)
-			root="${x#*=}"
-			;;
-		esac
-	done
-
-	# Make sure the device has been created by udev before we try to mount
-	wait-for-root "$root" "${ROOTDELAY:-180}" || panic "unable to find root partition '$root'"
-
-	[ -n "$root" ] || panic "no root partition specified"
-
-	if echo "$root" | grep -q ^/; then
-		path="$root"
-	else
-		# convert UUID/LABEL to a device name
-		path=$(findfs "$root" 2>/dev/null || :)
-	fi
-
-	[ -e "$path" ] || panic "root device $path does not exist"
-
-	# Mount the root filesystem read-only.
-	echo "initrd: mounting $path" >/dev/kmsg || true
-	mount -o defaults,ro "$path" "$rootmnt"
-
-	rootpath="$path"
-
-	# Create a read-only bind mount on top of the already read-only
-	# FS. This is to stop the system from noticing when the root
-	# filesystem is made writable (when system updates are applied).
-	mount -o bind,ro "$rootmnt" "$rootmnt"
-
-	echo "initrd: mounting /run" >/dev/kmsg || true
-	mount -o rw,nosuid,noexec,relatime,mode=755 -t tmpfs tmpfs "${rootmnt}/run"
-
-	mkdir -p "$writable_mnt"
+	local writable_label="$1"
+        local writable_mnt="$2"
 
 	path=$(get_partition_from_label "$writable_label")
 
@@ -226,9 +176,123 @@
 
 	echo "$(date '+%s'): end" >> "$logfile" || true
 
-	echo "initrd: mounting $writable_label partition" >/dev/kmsg || true
-	mount "$path" "$writable_mnt"
-	mkdir -p "${rootmnt}/writable"
+}
+
+# setup $rootmnt based on os/kernel snaps
+do_new_style_root_mounting()
+{
+        root="LABEL=writable"
+
+	# Make sure the device has been created by udev before we try to mount
+	wait-for-root "$root" "${ROOTDELAY:-180}" || panic "unable to find root partition '$root'"
+
+	[ -n "$root" ] || panic "no root partition specified"
+
+	if echo "$root" | grep -q ^/; then
+		path="$root"
+	else
+		# convert UUID/LABEL to a device name
+		path=$(findfs "$root" 2>/dev/null || :)
+	fi
+
+	[ -e "$path" ] || panic "root device $path does not exist"
+
+        # FIXME: meh, system should figure this out
+        #insmod ./lib/modules/*/kernel/fs/nls/nls_iso8859-1.ko
+        insmod ./lib/modules/*/kernel/fs/squashfs/squashfs.ko
+        
+        # mount writable rw
+        path=$(get_partition_from_label "$writable_label")
+        mount "$path" "$writable_mnt"
+
+        # mount OS snap
+        mount "${writable_mnt}/system-data/var/lib/snappy/snaps/${snappy_os}" "$rootmnt"
+
+        # now add a kernel bind mounts to it
+        local kernel_mnt="/tmpmnt_kernel"
+        mkdir -p "$kernel_mnt"
+        mount "${writable_mnt}/system-data/var/lib/snappy/snaps/${snappy_kernel}" "$kernel_mnt"
+        for d in modules firmware; do
+            mount -o bind "${kernel_mnt}/lib/$d" "$rootmnt/lib/$d"            
+        done
+}    
+
+# setup $rootmnt from system_ab style
+do_old_style_root_mounting()
+{
+	# Make sure the device has been created by udev before we try to mount
+	wait-for-root "$root" "${ROOTDELAY:-180}" || panic "unable to find root partition '$root'"
+
+	[ -n "$root" ] || panic "no root partition specified"
+
+	if echo "$root" | grep -q ^/; then
+		path="$root"
+	else
+		# convert UUID/LABEL to a device name
+		path=$(findfs "$root" 2>/dev/null || :)
+	fi
+
+	[ -e "$path" ] || panic "root device $path does not exist"
+
+	# Mount the root filesystem read-only.
+	echo "initrd: mounting $path" >/dev/kmsg || true
+	mount -o defaults,ro "$path" "$rootmnt"
+
+	rootpath="$path"
+
+	# Create a read-only bind mount on top of the already read-only
+	# FS. This is to stop the system from noticing when the root
+	# filesystem is made writable (when system updates are applied).
+	mount -o bind,ro "$rootmnt" "$rootmnt"
+}
+    
+#---------------------------------------------------------------------
+# XXX: Entry point - called by the initramfs "/init" script.
+#---------------------------------------------------------------------
+mountroot()
+{
+set -x
+        pre_mountroot
+
+	[ "$quiet" != "y" ] && log_begin_msg "Running /scripts/local-premount"
+	run_scripts /scripts/local-premount
+	[ "$quiet" != "y" ] && log_end_msg
+        
+        # find what snappy-os version to use
+        for x in $(cat /proc/cmdline); do
+	    case "${x}" in
+                # new kernel/os snap vars
+		snappy_os=*)
+			snappy_os="${x#*=}"
+			;;
+		snappy_kernel=*)
+			snappy_kernel="${x#*=}"
+			;;
+                # old system-ab style
+		root=*)
+			root="${x#*=}"
+			;;
+		esac
+	done
+
+        # always ensure writable is in a good state
+        writable_label="writable"
+        writable_mnt="/tmpmnt_${writable_label}"
+	mkdir -p "$writable_mnt"
+        fsck_writable "$writable_label" "$writable_mnt"
+
+        # check if we are on a new os/kernel snap system or a old snappy_ab one
+        if [ -n "$snappy_os" ] && [ -n "$snappy_kernel" ]; then
+            do_new_style_root_mounting
+        else
+            do_old_style_root_mounting
+        fi
+        
+        # mount /run
+	echo "initrd: mounting /run" >/dev/kmsg || true
+	mount -o rw,nosuid,noexec,relatime,mode=755 -t tmpfs tmpfs "${rootmnt}/run"
+
+        # move /writable to its final destination
 	mount --move "$writable_mnt" "${rootmnt}/writable"
 
 	# Prepare the fstab
@@ -243,7 +307,11 @@
 		echo "# DO NOT EDIT THIS FILE BY HAND - YOUR CHANGES WILL BE OVERWRITTEN" >> "$fstab"
 		echo "# (See writable-paths(5) for details)" >> "$fstab"
 		echo "/dev/root / rootfs defaults,ro 0 0" >> "$fstab"
-
+                # FIXME: ideally we would mount /writable RO here and
+                #        let systemd do a "remount,rw" for us. unfortunately
+                #        this is not supported by systemd so we need to do
+                #        the RW mount and fsck dance etc here :/
+                echo "LABEL=writable /writable auto defaults 0 0" >> "$fstab"
 		handle_writable_paths "$writable_paths" "$fstab"
 	fi
 
@@ -273,6 +341,7 @@
 		fi
 	fi
 
+        # FIXME: the below can go away once we no longer support snappy_ab
 	# add an fstab entry to mount the "other" rootfs partition read-only
 	partition=$(findfs LABEL="system-b" 2>/dev/null || :)
 	abs_rootpath=$(readlink -f "$rootpath" || :)
@@ -281,11 +350,10 @@
 	else
 		other="$partition"
 	fi
-
 	if [ -n "$other" ]; then
 		echo "$other /writable/cache/system auto defaults,ro 0 0" >> "$fstab"
-	fi
-
+        fi
+        
 	# Mount the systemd overlay so that we have a complete root partition during boot
 	mkdir -p "${rootmnt}/writable/system-data/etc/systemd/system"
 	mount -o bind "${rootmnt}/writable/system-data/etc/systemd/system" "${rootmnt}/etc/systemd/system"