Merge lp:~saviq/cloud-initramfs-tools/nfs-support into lp:cloud-initramfs-tools

[Michał Sawicz]

add NFS support to overlayroot

This adds support for NFS-backed overlayroot

Configuration:

overlayroot=nfs:host=10.0.0.1,path=/srv/nfs-overlay

This suffers from bug #1039402 unfortunately, so it's not really workable until the bug is fixed.

[Scott Moser (smoser)]

Michał,
  Thanks for this. It generally looks fine to me. I'm OK to pull it into trunk, my only concern is bug 1039402.
  As I understand it, this is pretty much entirely broken without that bug fix in the kernel, right?

  If so, I'm just weary of pulling in code that is effectively "known broken". I'm not entirely opposed, especially if there is evidence that the kernel issue will be fixed. I'd definitely hold off on including it in ubuntu before raring release though.

  Thoughts?

[Michał Sawicz (saviq)]

W dniu 09.04.2013 16:05, Scott Moser pisze:
> Michał,
> Thanks for this. It generally looks fine to me. I'm OK to pull it into trunk, my only concern is bug 1039402.
> As I understand it, this is pretty much entirely broken without that bug fix in the kernel, right?

More or less, mounting with server-side locking supposedly helps, but
you can't actually mount it like that in initramfs, and I couldn't
remount later, so yeah.

> If so, I'm just weary of pulling in code that is effectively "known broken". I'm not entirely opposed, especially if there is evidence that the kernel issue will be fixed. I'd definitely hold off on including it in ubuntu before raring release though.
>
> Thoughts?

Perfectly agree. I mostly put it out there to get a feel whether I'm
getting anywhere with this. Holding off until the bug is fixed is perfect.

Thanks!
--
Michał Sawicz <email address hidden>
Canonical Services Ltd.

[Dustin Kirkland  (kirkland)]

On Tue, Apr 9, 2013 at 2:13 PM, Michał Sawicz
<email address hidden> wrote:
> W dniu 09.04.2013 16:05, Scott Moser pisze:
>> Michał,
>> Thanks for this. It generally looks fine to me. I'm OK to pull it into trunk, my only concern is bug 1039402.
>> As I understand it, this is pretty much entirely broken without that bug fix in the kernel, right?
>
> More or less, mounting with server-side locking supposedly helps, but
> you can't actually mount it like that in initramfs, and I couldn't
> remount later, so yeah.
>
>> If so, I'm just weary of pulling in code that is effectively "known broken". I'm not entirely opposed, especially if there is evidence that the kernel issue will be fixed. I'd definitely hold off on including it in ubuntu before raring release though.
>>
>> Thoughts?
>
> Perfectly agree. I mostly put it out there to get a feel whether I'm
> getting anywhere with this. Holding off until the bug is fixed is perfect.

I'm quite intrigued by the feature as well. Nice work. Cool idea. I
agree with publishing the branch and putting it into a holding state
until the kernel bug is fixed.

Cheers,
--
:-Dustin

[Scott Moser (smoser)]

Please excuse the harsh 'Rejected'.
I'm closing this right now because
a.) bug 1039402 makes it not really work
b.) i've moved code over to git.

If you want to re-submit, please feel free to do so to the git repo.

https://code.launchpad.net/~cloud-initramfs-tools/cloud-initramfs-tools/+git/cloud-initramfs-tools

Unmerged revisions

86. By Michał Sawicz on 2013-04-07

add NFS support to overlayroot

=== modified file 'overlayroot/etc/overlayroot.conf'
--- overlayroot/etc/overlayroot.conf	2012-08-29 00:51:40 +0000
+++ overlayroot/etc/overlayroot.conf	2013-04-07 12:04:24 +0000
@@ -66,6 +66,19 @@
 #      crypt:mapname=mapper,pass=foo,fstype=ext3,mkfs=1,dev=/dev/disk/by-label/my-jumpdrive,timeout=120
 #      crypt:dev=xvdb
 #
+#  * overlayroot=nfs:host=IP,path=SHARE
+#    mount IP:SHARE as overlayfs and write changes there
+#
+#    available parameters are:
+#     * host: default: "" [REQUIRED]
+#       use given server for backing filesystem.
+#     * path: default: "" [REQUIRED]
+#       use given share on the server for backing filesystem.
+#     * see COMMON PARAMETERS
+#
+#    examples:
+#      overlayroot=nfs:host=10.0.0.1,path=/srv/nfs-overlay
+#
 #  * overlayroot=disabled
 #    if set explicitly to 'disabled', or an empty string, then
 #    overlayroot will do nothing.
 
=== modified file 'overlayroot/scripts/init-bottom/overlayroot'
--- overlayroot/scripts/init-bottom/overlayroot	2012-08-29 01:42:00 +0000
+++ overlayroot/scripts/init-bottom/overlayroot	2013-04-07 12:04:24 +0000
@@ -258,6 +258,26 @@
 	_RET_DEVICE="$dev"
 }
 
+nfs_setup() {
+	local options="$1" host="" path="/"
+	# options supported:
+	#    host=ip,path=/
+	parse_string "${options}" ||
+		{ log_fail "failed parsing '${options}'"; return 1; }
+
+	host=${_RET_host:-${host}}
+        path=${_RET_path:-${path}}
+
+	[ -n "$host" ] ||
+		{ log_fail "host= argument not provided in '${options}'"; return 1; }
+	[ -n "$path" ] ||
+		{ log_fail "path= argument not provided in '${options}'"; return 1; }
+
+	debug "host=${host} path=${path}"
+
+	_RET_DEVICE="${host}:${path}"
+}
+
 overlayrootify_fstab() {
 	# overlayrootify_fstab(input, root_ro, root_rw, dir_prefix, recurse, swap)
 	# read input fstab file, write an overlayroot version to stdout
@@ -504,6 +524,13 @@
 		mode="device"
 		device="$_RET_DEVICE"
 		;;
+	nfs:*)
+		mode="nfs"
+		opts=${overlayroot#nfs:}
+		nfs_setup "${opts}" ||
+			fail "failed setup overlay for ${overlayroot}${cfgmsg}"
+		device="$_RET_DEVICE"
+		;;
 	crypt:*)
 		mode="crypt"
 		opts=${overlayroot#crypt:}
@@ -573,6 +600,10 @@
 	# mount a tmpfs using the device name tmpfs-root
 	mount -t tmpfs tmpfs-root "${root_rw}" ||
 		fail "failed to create tmpfs"
+elif [ "$mode" = "nfs" ]; then
+        # mount the nfs share
+        nfsmount -o nolock "$device" "${root_rw}" ||
+                fail "failed mount backing share $device"
 else
 	# dev or crypto
 	mount "$device" "${root_rw}" ||