Add ostree.write deployment extension

This is a simple deployment extension to write the results of a Baserock
build to an OSTree repo.

See ostree.write.help for more information.

The Baserock reference systems contain static device nodes, which are
not supported by OSTree, and are obsolete on Linux systems. To work
around this problem, I added a strip-device-nodes.configure extension.
The systems should still work the same as devtmpfs will create the
device nodes.

I've tested this by deploying minimal-system-x86_64 to an OSTree repo,
then checking it out into a temporary directory, creating a read-only
bind-mount of the temporary directory and chrooting then into it.

This is only going to be useful for containers systems and chroots for
the time being. We would need to make some quite major changes to the
Baserock reference systems to enable deployment to VMs or bare metal
using OSTree.

Change-Id: I8556139d118da759360cdc1ce998590b1f50b644

1 files changed, 73 insertions, 0 deletions

diff --git a/extensions/ostree.write.help b/extensions/ostree.write.help
new file mode 100644
index 00000000..90a181be
--- /dev/null
+++ b/extensions/ostree.write.help
@@ -0,0 +1,73 @@
+# Copyright (C) 2015 Codethink Limited
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; version 2 of the License.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along
+# with this program; if not, see <http://www.gnu.org/licenses/>.
+
+help: |
+
+    Deploy a Baserock system to an existing OSTree repository.
+
+    Parameters:
+
+    * location: the path to the OSTree repo.
+
+    * OSTREE_BRANCH=branchname: the branch to commit to
+
+    * OSTREE_COMMIT_SUBJECT=subject: one-line commit title
+
+    * OSTREE_COMMIT_BODY=text: full commit message (optional)
+
+    See `morph help deploy` for details of how to pass parameters to write
+    extensions.
+
+    This extension requires a local OSTree repository to deploy to, which must
+    already exist. You can create a new repository using the `ostree init`
+    command.
+
+    If you want to deploy straight to the local machine, you should use a
+    'bare' mode repository, which allows the resulting system to be quickly
+    checked out.
+
+    If you want to serve the results of a deployment from an OSTree server,
+    you need to use a local 'archive-z2' mode repository. You can then use
+    `ostree pull` on the server to pull the results of the deployment from the
+    build machine. Note that 'push' style transfers are not currently supported
+    by OSTree.
+
+    For full OSTree documentation, see <https://wiki.gnome.org/Projects/OSTree>.
+
+    IMPORTANT NOTE: OSTree can only store regular files. It cannot store device
+    nodes. If your system contains static device nodes (which all of the
+    Baserock reference systems do, at time of writing) you can use the
+    strip-device-nodes.configure extension to remove them, and leave devtmpfs
+    to create the device nodes.
+
+    If you seen an error like "Not a regular file or symlink: null.", you have
+    hit this problem.
+
+    ANOTHER IMPORTANT NOTE: OSTree uses hardlinks to checkout files quickly.
+    This has an important consequence: any files checked out from OSTree MUST
+    not be overwritten at runtime, or you *will* cause corruption in the
+    repository and/or your checked-out system. In general, if you want to
+    use OSTree for container systems or chroots, it is enough to create a
+    read-only bindmount:
+
+        mount --bind ./ostree-checkout-dir ./sysroot-dir
+        mount -o bind,remount,ro ./sysroot-dir
+
+    If you want to run a system using OSTree as the real OS of a system, you
+    are best off following this guide:
+
+        https://developer.gnome.org/ostree/stable/adapting-existing.html
+
+    This extension requires that the libostree-1 library and the Python
+    GObject-introspection bindings are available.