This class provides an image feature that mounts /etc as an overlayfs
file system. This is an extension for existing overlayfs class, which
doesn't support /etc
Signed-off-by: Alfred Schapansky <alfred.schapan...@avantys.de>
Signed-off-by: Vyacheslav Yurkov <uvv.m...@gmail.com>
---
meta/classes/overlayfs-etc.bbclass | 76 ++++++++++++++++++++++++++++++
1 file changed, 76 insertions(+)
create mode 100644 meta/classes/overlayfs-etc.bbclass
diff --git a/meta/classes/overlayfs-etc.bbclass
b/meta/classes/overlayfs-etc.bbclass
new file mode 100644
index 0000000000..5e89339269
--- /dev/null
+++ b/meta/classes/overlayfs-etc.bbclass
@@ -0,0 +1,76 @@
+# Class for setting up /etc in overlayfs
+#
+# In order to have /etc directory in overlayfs a special handling at early
boot stage is required
+# The idea is to supply a custom init script that mounts /etc before launching
actual init program,
+# because the latter already requires /etc to be mounted
+#
+# The configuration must be machine specific. You should at least set these
three variables:
+# OVERLAYFS_ETC_MOUNT_POINT ?= "/data"
+# OVERLAYFS_ETC_FSTYPE ?= "ext4"
+# OVERLAYFS_ETC_DEVICE ?= "/dev/mmcblk0p2"
+#
+# To control more mount options you should consider setting mount options:
+# OVERLAYFS_ETC_MOUNT_OPTIONS ?= "defaults"
+#
+# The class provides two options for /sbin/init generation
+# 1. Default option is to rename original /sbin/init to /sbin/init.orig and
place generated init under
+# original name, i.e. /sbin/init. It has an advantage that you won't need
to change any kernel
+# parameters in order to make it work, but it poses a restriction that
package-management can't
+# be used, becaause updating init manager would remove generated script
+# 2. If you are would like to keep original init as is, you can set
+# OVERLAYFS_ETC_USE_ORIG_INIT_NAME = "0"
+# Then generated init will be named /sbin/preinit and you would need to
extend you kernel parameters
+# manually in your bootloader configuration.
+#
+# Regardless which mode you choose, update and migration strategy of
configuration files under /etc
+# overlay is out of scope of this class
+
+ROOTFS_POSTPROCESS_COMMAND += '${@bb.utils.contains("IMAGE_FEATURES",
"overlayfs-etc", "create_overlayfs_etc_preinit;", "", d)}'
+IMAGE_FEATURES_CONFLICTS_overlayfs-etc = "package-management"
+
+OVERLAYFS_ETC_MOUNT_POINT ??= ""
+OVERLAYFS_ETC_FSTYPE ??= ""
+OVERLAYFS_ETC_DEVICE ??= ""
+OVERLAYFS_ETC_USE_ORIG_INIT_NAME ??= "1"
+OVERLAYFS_ETC_MOUNT_OPTIONS ??= "defaults"
+OVERLAYFS_ETC_INIT_TEMPLATE ??= "${COREBASE}/meta/files/preinit.sh.in"
+
+python create_overlayfs_etc_preinit() {
+ overlayEtcMountPoint = d.getVar("OVERLAYFS_ETC_MOUNT_POINT")
+ overlayEtcFsType = d.getVar("OVERLAYFS_ETC_FSTYPE")
+ overlayEtcDevice = d.getVar("OVERLAYFS_ETC_DEVICE")
+
+ if not overlayEtcMountPoint:
+ bb.fatal("OVERLAYFS_ETC_MOUNT_POINT must be set in your MACHINE
configuration")
+ if not overlayEtcDevice:
+ bb.fatal("OVERLAYFS_ETC_DEVICE must be set in your MACHINE
configuration")
+ if not overlayEtcFsType:
+ bb.fatal("OVERLAYFS_ETC_FSTYPE should contain a valid file system type
on {0}".format(overlayEtcDevice))
+
+ with open(d.getVar("OVERLAYFS_ETC_INIT_TEMPLATE"), "r") as f:
+ PreinitTemplate = f.read()
+
+ useOrigInit =
oe.types.boolean(d.getVar('OVERLAYFS_ETC_USE_ORIG_INIT_NAME'))
+ preinitPath = oe.path.join(d.getVar("IMAGE_ROOTFS"),
d.getVar("base_sbindir"), "preinit")
+ initBaseName = oe.path.join(d.getVar("base_sbindir"), "init")
+ origInitNameSuffix = ".orig"
+
+ args = {
+ 'OVERLAYFS_ETC_MOUNT_POINT': overlayEtcMountPoint,
+ 'OVERLAYFS_ETC_MOUNT_OPTIONS': d.getVar('OVERLAYFS_ETC_MOUNT_OPTIONS'),
+ 'OVERLAYFS_ETC_FSTYPE': overlayEtcFsType,
+ 'OVERLAYFS_ETC_DEVICE': overlayEtcDevice,
+ 'SBIN_INIT_NAME': initBaseName + origInitNameSuffix if useOrigInit
else initBaseName
+ }
+
+ if useOrigInit:
+ # rename original /sbin/init
+ origInit = oe.path.join(d.getVar("IMAGE_ROOTFS"), initBaseName)
+ bb.debug(1, "rootfs path %s, init path %s, test %s" %
(d.getVar('IMAGE_ROOTFS'), origInit, d.getVar("IMAGE_ROOTFS")))
+ bb.utils.rename(origInit, origInit + origInitNameSuffix)
+ preinitPath = origInit
+
+ with open(preinitPath, 'w') as f:
+ f.write(PreinitTemplate.format(**args))
+ os.chmod(preinitPath, 0o755)
+}
--
2.28.0
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