volatile-binds: add recipe

This recipe is designed to play a key role in a read-only rootfs
of systemd based systems. It generates service files from a template,
volatile-binds.service.in and the VOLATILE_BINDS variable.

By default, VOLATILE_BINDS takes the value of "/var/volatile/lib /var/lib\n",
which leads to the generation of volatile-var-lib.service file.
This file doesn't have any effect in a read-write system, as it
has "ConditionPathIsReadWrite = !/var/lib" in the [Unit] section.
In other words, this file only has effect in a read-only rootfs.

Signed-off-by: Chen Qi <Qi.Chen@windriver.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>

3 files changed, 70 insertions, 0 deletions

diff --git a/meta/recipes-core/volatile-binds/files/COPYING.MIT b/meta/recipes-core/volatile-binds/files/COPYING.MIT
new file mode 100644
index 0000000000..7e7d57413d
--- /dev/null
+++ b/meta/recipes-core/volatile-binds/files/COPYING.MIT
@@ -0,0 +1,17 @@
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR
+THE USE OR OTHER DEALINGS IN THE SOFTWARE.
diff --git a/meta/recipes-core/volatile-binds/files/mount-copybind b/meta/recipes-core/volatile-binds/files/mount-copybind
new file mode 100755
index 0000000000..2aeaf84ddb
--- /dev/null
+++ b/meta/recipes-core/volatile-binds/files/mount-copybind
@@ -0,0 +1,34 @@
+#!/bin/sh
+#
+# Perform a bind mount, copying existing files as we do so to ensure the
+# overlaid path has the necessary content.
+
+if [ $# -lt 2 ]; then
+    echo >&2 "Usage: $0 spec mountpoint [OPTIONS]"
+    exit 1
+fi
+
+spec=$1
+mountpoint=$2
+
+if [ $# -gt 2 ]; then
+    options=$3
+else
+    options=
+fi
+
+[ -n "$options" ] && options=",$options"
+
+mkdir -p "${spec%/*}"
+if [ -d "$mountpoint" ]; then
+    if [ ! -d "$spec" ]; then
+        mkdir "$spec"
+        cp -pPR "$mountpoint"/. "$spec/"
+    fi
+elif [ -f "$mountpoint" ]; then
+    if [ ! -f "$spec" ]; then
+        cp -pP "$mountpoint" "$spec"
+    fi
+fi
+
+mount -o "bind$options" "$spec" "$mountpoint"
diff --git a/meta/recipes-core/volatile-binds/files/volatile-binds.service.in b/meta/recipes-core/volatile-binds/files/volatile-binds.service.in
new file mode 100644
index 0000000000..32be5b4425
--- /dev/null
+++ b/meta/recipes-core/volatile-binds/files/volatile-binds.service.in
@@ -0,0 +1,19 @@
+[Unit]
+Description=Bind mount volatile @where@
+DefaultDependencies=false
+Before=local-fs.target
+RequiresMountsFor=@whatparent@ @whereparent@
+ConditionPathIsReadWrite=@whatparent@
+ConditionPathExists=@where@
+ConditionPathIsReadWrite=!@where@
+
+[Service]
+Type=oneshot
+RemainAfterExit=Yes
+StandardOutput=syslog
+TimeoutSec=0
+ExecStart=/sbin/mount-copybind @what@ @where@
+ExecStop=/sbin/umount @where@
+
+[Install]
+WantedBy=local-fs.target